Showing papers on "Plant physiology published in 2019"
TL;DR: It is found that the past planting record had a significant effect on the assembly of the microbial community in the peanut rhizosphere, indicating a soil memory effect, and suggests that land use history affects croprhizosphere microbiomes and plant physiology.
Abstract: Microorganisms associated with roots are thought to be part of the so-called extended plant phenotypes with roles in the acquisition of nutrients, production of growth hormones, and defense against diseases. Since the crops selectively enrich most rhizosphere microbes out of the bulk soil, we hypothesized that changes in the composition of bulk soil communities caused by agricultural management affect the extended plant phenotype. In the current study, we performed shotgun metagenome sequencing of the rhizosphere microbiome of the peanut (Arachis hypogaea) and metatranscriptome analysis of the roots of peanut plants grown in the soil with different management histories, peanut monocropping and crop rotation. We found that the past planting record had a significant effect on the assembly of the microbial community in the peanut rhizosphere, indicating a soil memory effect. Monocropping resulted in a reduction of the rhizosphere microbial diversity, an enrichment of several rare species, and a reduced representation of traits related to plant performance, such as nutrients metabolism and phytohormone biosynthesis. Furthermore, peanut plants in monocropped soil exhibited a significant reduction in growth coinciding with a down-regulation of genes related to hormone production, mainly auxin and cytokinin, and up-regulation of genes related to the abscisic acid, salicylic acid, jasmonic acid, and ethylene pathways. These findings suggest that land use history affects crop rhizosphere microbiomes and plant physiology.
134 citations
TL;DR: The results of this study revealed that the inoculation of plants by ACC deaminase-producing PGPEs is a potential tool for the enhancement of plant growth and stress tolerance.
130 citations
TL;DR: This review will recapitulate the responses of the photosynthetic machinery to biotic stress factors, from pathogens (viruses, bacteria, and fungi) to pests (herbivory) analyzed by chlorophyll fluorescence imaging both at the lab and field scale.
Abstract: Photosynthesis is a pivotal process in plant physiology, and its regulation plays an important role in plant defense against biotic stress. Interactions with pathogens and pests often cause alterations in the metabolism of sugars and sink/source relationships. These changes can be part of the plant defense mechanisms to limit nutrient availability to the pathogens. In other cases, these alterations can be the result of pests manipulating the plant metabolism for their own benefit. The effects of biotic stress on plant physiology are typically heterogeneous, both spatially and temporarily. Chlorophyll fluorescence imaging is a powerful tool to mine the activity of photosynthesis at cellular, leaf, and whole-plant scale, allowing the phenotyping of plants. This review will recapitulate the responses of the photosynthetic machinery to biotic stress factors, from pathogens (viruses, bacteria, and fungi) to pests (herbivory) analyzed by chlorophyll fluorescence imaging both at the lab and field scale. Moreover, chlorophyll fluorescence imagers and alternative techniques to indirectly evaluate photosynthetic traits used at field scale are also revised.
114 citations
TL;DR: Pi-stressed plants are susceptible to colonization by latent opportunistic competitors found within their microbiome, thus exacerbating the plant’s Pi starvation.
Abstract: Phosphate starvation response (PSR) in nonmycorrhizal plants comprises transcriptional reprogramming resulting in severe physiological changes to the roots and shoots and repression of plant immunity. Thus, plant-colonizing microorganisms-the plant microbiota-are exposed to direct influence by the soil's phosphorus (P) content itself as well as to the indirect effects of soil P on the microbial niches shaped by the plant. The individual contribution of these factors to plant microbiota assembly remains unknown. To disentangle these direct and indirect effects, we planted PSR-deficient Arabidopsis mutants in a long-term managed soil P gradient and compared the composition of their shoot and root microbiota to wild-type plants across different P concentrations. PSR-deficiency had a larger effect on the composition of both bacterial and fungal plant-associated microbiota than soil P concentrations in both roots and shoots. To dissect plant-microbe interactions under variable P conditions, we conducted a microbiota reconstitution experiment. Using a 185-member bacterial synthetic community (SynCom) across a wide P concentration gradient in an agar matrix, we demonstrated a shift in the effect of bacteria on the plant from a neutral or positive interaction to a negative one, as measured by rosette size. This phenotypic shift was accompanied by changes in microbiota composition: the genus Burkholderia was specifically enriched in plant tissue under P starvation. Through a community drop-out experiment, we demonstrated that in the absence of Burkholderia from the SynCom, plant shoots accumulated higher ortophosphate (Pi) levels than shoots colonized with the full SynCom but only under Pi starvation conditions. Therefore, Pi-stressed plants are susceptible to colonization by latent opportunistic competitors found within their microbiome, thus exacerbating the plant's Pi starvation.
110 citations
TL;DR: Salinity stress and Cu exposure may change the primary metabolic pathways in favor of major volatile oil components biosynthesis, resulting in significant changes of essential oil yield and composition.
93 citations
TL;DR: In this article, the potential effects of yeast and carrot extracts, and their associated mechanisms in the alleviation of seawater-induced salt stress in maize, were investigated, and it was shown that pretreatment of maize seeds with yeast or carrot extract provided maize plants with enormous abilities in reducing growth inhibition and biomass loss when exposed to seawater.
Abstract: Damage to plant productivity due to soil salinity is a major agricultural problem, necessitating the development of effective salinity management measures. Here, we sought the potential effects of yeast and carrot extracts, and their associated mechanisms in the alleviation of seawater-induced salt stress in maize. Pretreatment of maize seeds with yeast or carrot extract provided maize plants with enormous abilities in reducing growth inhibition and biomass loss when exposed to seawater. The better growth performance of yeast extract- and carrot extract-primed plants under saline conditions coincided with improved protection of the photosynthetic pigments, chlorophylls and carotenoids. The primed plants also restricted Na+ accumulation in both roots and shoots while maintaining a higher K+ content and lower Na+/K+ ratio when compared with that of non-primed plants. Yeast extract and carrot extract also potentiated salt tolerance mechanisms by accelerating the production of osmolytes, as evidenced by accumulating levels of total free amino acids and soluble sugars, especially in the roots of primed plants during salinity. The enhanced levels of ascorbic acid and phenolic compounds, and the heightened activities of reactive oxygen species-detoxifying enzymes superoxide dismutase, catalase, and ascorbate peroxidase with concurrent reduction of lipid peroxidation in the leaves of primed plants clearly indicated a positive impact of yeast extract- and carrot extract-priming on the antioxidant system of maize under salt stress. Our results together suggest decisive roles of yeast extract and carrot extract in the management of salt-induced adverse effects in economically important maize, and perhaps other crops.
64 citations
TL;DR: The presence of Methylobacterium significantly enhanced the performance of lentils exposed to drought by stimulating early growth of shoots and roots and increasing photosynthetic rates, and improving Harvest Index.
49 citations
TL;DR: In this article, Hartmannibacter and Pseudomonas sp. were used to inoculate plants of alfalfa cultivars to mitigate the harmful effects of salinity on plants growth.
Abstract: Alfalfa (Medicago sativa L.) plant growth decreases when cultivated under salinity or irrigated with salty water. Inoculation with plant growth-promoting bacteria (PGPB) is a method for mitigating the harmful effects of salinity on plants growth. To investigate salt-tolerant PGPB with salt-tolerant and salt-sensitive alfalfa cultivar interactions under salinity, some physiological and agronomical aspects were investigated. The inoculated plants of alfalfa cultivars with Hartmannibacter. diazotrophicus and Pseudomonas sp. bacteria were compared with non-inoculated plants. Plants were grown in growth room and irrigated with tap water until 6–7 weeks, and then, salinity stress imposed by irrigating with tap water (control), 10 dS m−1 and 20 dS m−1 NaCl. Salinity reduced relative water content (RWC), membrane stability index (MSI), K+, photosynthesis rate (Pn) and stomatal conductance (gs), leaf number, height, and dry weight, and increased sodium in all cultivars. Inoculation of cultivars with both PGPB mitigated the negative effects of salinity on plants growth by increasing the root length and weight, nodule number, chlorophyll pigments, RWC, MSI, Pn, and gs. Chlorophyll pigments, plant height and leaf number, Na+, K+/Na+, and nodule number improved more pronounced through inoculating with Pseudomonas sp., whereas K+, carotenoids, and RWC improved more pronounced through H. diazotrophicus under salinity. The results showed inoculation with two bacteria improved growth performance in salt-tolerant and salt-sensitive cultivars under 10 dS m−1, but at high salinity (20 dS m−1), inoculation was successful only in salt-tolerant alfalfa cultivars.
47 citations
TL;DR: The role of drought tolerant PGPR namely, Pseudomonas simiae strain AU, in protection of soybean plants by modulating the gene expression profile and phytohormone biosynthesis responsible for drought tolerance in plants is emphasized.
Abstract: Plant growth promoting rhizobacteria (PGPR) have been described for sustainable agriculture practices as being a vital agent for abiotic and biotic stress mitigation and growth promotion in plants. In the present research, the authors emphasize the role of drought tolerant PGPR namely, Pseudomonas simiae strain AU, in protection of soybean plants by modulating the gene expression profile and phytohormone biosynthesis responsible for drought tolerance in plants. The gene expression analysis confirmed the involvement of transcription factors (DREB/EREB), osmoprotectants (P5CS, GOLS), and water transporters (PIP & TIP), as these genes were up-regulated in P. simiae AU-inoculated plants leading to drought tolerance. In addition, enhanced production of abscisic acid (ABA) and salicylic acid (SA) hormones and reduction of ethylene emission, associated with promoting drought tolerance, was observed in bacterial-inoculated plants in comparison to non-inoculated plants. Higher proline and total soluble sugar contents in AU-inoculated soybean plants also contributed to increased tolerance to drought stress. Overall, P. simiae AU mediated drought-induced expression profiles of stress genes and plant hormones were determined in soybean plants.
42 citations
TL;DR: It is found that the improved wheat plant growth, photosynthesis and nutrient accumulations by the inoculation of Alternaria alternata LQ1230 might be attributed to the reprogramming of wheat plant metabolism, thus enhancing wheat drought tolerance.
Abstract: Endophytic fungi colonization is an eco-friendly strategy to respond to environmental stresses and confer tolerance to the host plant. Here, the responses of wheat plant inoculated with an indole acetic acid (IAA) -producing endophytic fungus to drought stress and water recovery were evaluated. The inoculation of wheat plants with Alternaria alternata (LQ1230) was conducted to evaluate drought resistance under adequate water, water deficit and water recovery conditions by examining the growth parameters and various physiological indicators of wheat seedlings. The LQ1230 isolated from Elymus dahuricus Turcz could secrete indole acetic acid (IAA) by both the tryptophan-dependent (319.24 ± 14.88 μg/mL) and independent (40.12 ± 8.59 μg/mL) pathways. LQ1230 inoculation enhanced wheat growth and drought tolerance through regulation of antioxidant enzyme activities and the content of compatible solutes such as soluble sugars and proline. Additionally, LQ1230 inoculated plants demonstrated significantly improved photosynthesis, C and N accumulation of wheat plants, leading to a positive relationship with plant dry biomass under water deficit and re-watering conditions. We found that the improved wheat plant growth, photosynthesis and nutrient accumulations by the inoculation of Alternaria alternata LQ1230 might be attributed to the reprogramming of wheat plant metabolism, thus enhancing wheat drought tolerance. Inoculation with fungal endophytes such as LQ1230 has the potential to increase crop drought resistance.
41 citations
TL;DR: Characteristics that promote plant growth were explored for their ability to enhance the growth of peanut plants under N2 deficit condition and results indicate that plants co-cultivated with PGPR, S. maltophilia, increase plant growth, antioxidant levels, scavenging, and stress tolerance under N1 deficit condition.
Abstract: Arachis hypogea (Peanut) is one of the most important crops, and it is harvested and used for food and oil production. Being a legume crop, the fixation of atmospheric nitrogen is achieved through symbiotic association. Nitrogen deficiency is one of the major constrains for loss of crop productivity. The bacterium Stenotrophomonas maltophilia is known for interactions with plants. In this study, characteristics that promote plant growth were explored for their ability to enhance the growth of peanut plants under N2 deficit condition. In the presence of S. maltophilia, it was observed that fatty acid composition of peanut plants was influenced and increased contents of omega-7 monounsaturated fatty acid and omega-6 fatty acid (γ-Linolenic acid) were detected. Plant growth was increased in plants co-cultivated with PGPR (Plant Growth Promoting Rhizobacteria) under normal and stress (nitrogen deficient) condition. Electrolyte leakage, lipid peroxidation, and H2O2 content reduced in plants, co-cultivated with PGPR under normal (grown in a media supplemented with N2 source; C+) or stress (nitrogen deficient N+) conditions compared to the corresponding control plants (i.e. not co-cultivated with PGPR; C-or N-). The growth hormone auxin, osmoprotectants (proline, total soluble sugars and total amino acids), total phenolic-compounds and total flavonoid content were enhanced in plants co-cultivated with PGPR. Additionally, antioxidant and free radical scavenging (DPPH, hydroxyl and H2O2) activities were increased in plants that were treated with PGPR under both normal and N2 deficit condition. Overall, these results indicate that plants co-cultivated with PGPR, S. maltophilia, increase plant growth, antioxidant levels, scavenging, and stress tolerance under N2 deficit condition. The beneficial use of bacterium S. maltophilia could be explored further as an efficient PGPR for growing agricultural crops under N2 deficit conditions. However, a detail agronomic study would be prerequisite to confirm its commercial role.
TL;DR: Investigation of the interactions between the ABA biosynthesis genes PpNCED2/3 and the ethylene response transcription factor PpERF3 in peach fruit suggests that ethylene promotes A BA biosynthesis through Pp ERF3’s regulation of the expression of ABAenes, and may help in finding ways to prolong fruit shelf life.
Abstract: The plant hormone ethylene regulates ripening in climacteric fruits. The phytohormone abscisic acid (ABA) affects ethylene biosynthesis, but whether ethylene influences ABA biosynthesis is unknown. To explore this possibility, we investigated the interactions between the ABA biosynthesis genes PpNCED2/3 and the ethylene response transcription factor PpERF3 in peach fruit. The ABA content increased during fruit maturation and reached a peak at stage S4 III. The increase was greatly inhibited by the ethylene inhibitor 1-MCP, which also suppressed PpERF3 expression. PpERF3 shared a similar expression profile with PpNCED2/3, encoding a rate-limiting enzyme involved in ABA biosynthesis, during fruit ripening. A yeast one-hybrid assay suggested that the nuclear-localized PpERF3 might bind to the promoters of PpNCED2/3. PpERF3 increased the expression of PpNCED2/3 as shown by dual-luciferase reporters, promoter-GUS assays and transient expression analyses in peach fruit. Collectively, these results suggest that ethylene promotes ABA biosynthesis through PpERF3’s regulation of the expression of ABA biosynthesis genes PpNCED2/3. Two hormones that regulate fruit ripening are more closely linked than previously thought, according to a study of ripening in peaches. Ethylene is a key ripening hormone in many fruits, and high ethylene levels turn on ethylene response factors (ERFs), genes that trigger production of sugars, pigments, and flavor compounds associated with ripening. Another hormone, abscisic acid (ABA), has recently been found to affect ripening, but its interaction with ethylene is unclear. Zhiqiang Wang and Guohuai Li at the Chinese Academy of Agricultural Sciences and coworkers investigated how ethylene and ABA interact during ripening. They found that as ethylene levels increased, ABA production was stimulated. Further investigation showed that ethylene directly triggered the ABA increase via ERFs. These results illuminate the fruit ripening process, and may help in finding ways to prolong fruit shelf life.
TL;DR: It is reported that overexpression of OsARD1 elevates the endogenous ethylene release rate, enhances the tolerance to submergence stress, and reduces the sensitivity to drought, salt, and osmotic stresses in rice.
Abstract: Acireductone dioxygenase (ARD) is a metal-binding metalloenzyme and involved in the methionine salvage pathway. In rice, OsARD1 binds Fe2+ and catalyzes the formation of 2-keto-4-methylthiobutyrate (KMTB) to produce methionine, which is an initial substrate in ethylene synthesis pathway. Here, we report that overexpression of OsARD1 elevates the endogenous ethylene release rate, enhances the tolerance to submergence stress, and reduces the sensitivity to drought, salt, and osmotic stresses in rice. OsARD1 is strongly induced by submergence, drought, salinity, PEG6000, and mechanical damage stresses and exhibits high expression level in senescent leaves. Transgenic plants overexpressing OsARD1 (OsARD1-OE) display fast elongation growth to escape submergence stress. The ethylene content is significantly maximized in OsARD1-OE plants compared with the wide type. OsARD1-OE plants display increased shoot elongation and inhibition of root elongation under the submergence stress and grow in dark due to increase of ethylene. The elongation of coleoptile under anaerobic germination is also significantly promoted in OsARD1-OE lines due to the increase of ethylene content. The sensitivity to drought and salt stresses is reduced in OsARD1-OE transgenic lines. Water holding capacity is enhanced, and the stomata and trichomes on leaves increase in OsARD1-OE lines. Drought and salt tolerance and ethylene synthesis-related genes are upregulated in OsARD1-OE plants. Subcellular localization shows that OsARD1 displays strong localization signal in cell nucleus, suggesting OsARD1 may interact with the transcription factors. Taken together, the results provide the understanding of the function of OsARD1 in ethylene synthesis and abiotic stress response in rice.
TL;DR: It is concluded that overexpression of SiDHN gene can promote cold and drought tolerance of transgenic tomato plants by inhibiting cell membrane damage, protecting chloroplasts, and enhancing the reactive oxygen species scavenging capacity.
Abstract: Dehydrins are late embryogenesis abundant proteins that help regulate abiotic stress responses in plants. Overexpression of the Saussurea involucrata dehydrin gene SiDHN has previously been shown to improve water-use efficiency and enhance cold and drought tolerance of transgenic tobacco. To understand the mechanism by which SiDHN exerts its protective function, we transformed the SiDHN gene into tomato plants (Solanum lycopersicum L.) and assessed their response to abiotic stress. We observed that in response to stresses, the SiDHN transgenic tomato plants had increased contents of chlorophyll a and b, carotenoid and relative water content compared with wild-type plants. They also had higher maximal photochemical efficiency of photosystem II and accumulated more proline and soluble sugar. Compared to those wild-type plants, malondialdehyde content and relative electron leakage in transgenic plants were not significantly increased, and H2O2 and O2- contents in transgenic tomato plants were significantly decreased. We further observed that the production of stress-related antioxidant enzymes, including superoxide dismutase, ascorbate peroxidase, peroxidase, and catalase, as well as pyrroline-5-carboxylate synthetase and lipid transfer protein 1, were up-regulated in the transgenic plants under cold and drought stress. Based on these observations, we conclude that overexpression of SiDHN gene can promote cold and drought tolerance of transgenic tomato plants by inhibiting cell membrane damage, protecting chloroplasts, and enhancing the reactive oxygen species scavenging capacity. The finding can be beneficial for the application of SiDHN gene in improving crop tolerance to abiotic stress and oxidative damage.
TL;DR: In this article, the effects of plant treatment with a donor of hydrogen sulfide (sodium hydrosulfide) on the state of antioxidative and osmoprotective systems of young plants of winter wheat (Triticum aestivum L.) cv. Doskonala under conditions of soil drought (progressive decrease in soil moisture down to 25-30% of the total moisture capacity) were studied.
Abstract: Effects of plant treatment with a donor of hydrogen sulfide—sodium hydrosulfide—on the state of antioxidative and osmoprotective systems of young plants of winter wheat (Triticum aestivum L.) cv. Doskonala under conditions of soil drought (progressive decrease in soil moisture down to 25–30% of the total moisture capacity) were studied. Spraying of plants with NaHS solutions (0.1–0.5 mM) before the drought significantly alleviated the growth suppression and favored the conservation of the chlorophyll pool under drought conditions. The beneficial effect of sodium hydrosulfide on plants was eliminated by their simultaneous treatment with hydroxylamine, which is a scavenger of hydrogen sulfide. The plant pretreatment with NaHS prevented the drought-induced accumulation of hydrogen peroxide and that of a lipid peroxidation product (malonic dialdehyde) in leaves. Such pretreatment also promoted an increase in the activity of superoxide dismutase (SOD) and prevented a stress-induced decrease in activities of catalase and guaiacol peroxidase in the leaves. Furthermore, the hydrogen sulfide donor elevated the concentration of proline and considerably increased levels of anthocyanins and UV-absorbing flavonoids under the drought. It is concluded that the plant drought protection afforded by the hydrogen sulfide donor depends to large extent on SOD and flavonoid compounds.
TL;DR: In this article, the effects of brassinosteroids on woody plants, notably on photosynthesis and chloroplast ultrastructure, have received little attention, and the results suggest that treatment of black locust seedlings with 24-epiBL prior to planting may improve performance and aid establishment on salt-affected soils.
Abstract: The brassinosteroids (BRs) constitute a recently defined class of plant hormone that can enhance the resistance of plants to multiple stresses. However, the effects of BRs on salt-stressed woody plants, notably on photosynthesis and chloroplast ultrastructure, have received little attention. Black locust (Robinia pseudoacacia L.) seeds and seedlings were pretreated with 1.04 µmol L− 1 24-epibrassinolide (24-epiBL) by soaking and root dipping, respectively, and grown under non-saline or saline conditions (0, 100, 200 mmol L− 1 NaCl). Salinity stress decreased photosynthesis, chlorophyll concentration, transpiration, and stomatal conductance but also decreased the water-use efficiency, while chlorophyll fluorescence indicated a decrease in photochemical quenching and in maximum potential quantum efficiency. Indicators of oxidative stress (for example, H2O2 and antioxidant enzymes), membrane leakage, and amounts of Na+ ions in leaves and chloroplasts were increased and, at the highest stress, chloroplast ultrastructure was severely disrupted. Exogenous 24-epiBL improved membrane stability and reduced foliar Na+ levels, while substantially alleviating stress-induced changes in photosynthetic gas exchange. Improvements in chlorophyll content and indicators of oxidative stress were not as large but were still highly significant. Thylakoid membrane structure was protected. Both methods of applying 24-epiBL were effective, but root-dipped seedlings performed marginally better. The results suggest that treatment of black locust seedlings with 24-epiBL prior to planting may improve performance and aid establishment on salt-affected soils.
TL;DR: The pretreatment of whole tomato plants with α-ionone vapor decreased the survival rate of western flower thrips without exhibiting insecticidal activity and common cutworm larvae fed on α-IONone-treated tomato plants exhibited a reduction in weight.
Abstract: Apocarotenoids, such as β-cyclocitral, α-ionone, β-ionone, and loliolide, are derived from carotenes via chemical or enzymatic processes. Recent studies revealed that β-cyclocitral and loliolide play an important role in various aspects of plant physiology, such as stress responses, plant growth, and herbivore resistance. However, information on the physiological role of α-ionone is limited. We herein investigated the effects of α-ionone on plant protection against herbivore attacks. The pretreatment of whole tomato (Solanum lycopersicum) plants with α-ionone vapor decreased the survival rate of western flower thrips (Frankliniella occidentalis) without exhibiting insecticidal activity. Exogenous α-ionone enhanced the expression of defense-related genes, such as basic β-1,3-glucanase and basic chitinase genes, in tomato leaves, but not that of jasmonic acid (JA)- or loliolide-responsive genes. The pretreatment with α-ionone markedly decreased egg deposition by western flower thrips in the JA-insensitive Arabidopsis (Arabidopsis thaliana) mutant coi1-1. We also found that common cutworm (Spodoptera litura) larvae fed on α-ionone-treated tomato plants exhibited a reduction in weight. These results suggest that α-ionone induces plant resistance to western flower thrips through a different mode of action from that of JA and loliolide.
TL;DR: The proposed in vitro infection model could be used to identify novel bioactive compounds and/or to select specific endophytes contributing to the host metabolism properties to influence bacterial colonization specificity and plant growth.
Abstract: Echinacea-endophyte interaction might affect plant secondary metabolites content and influence bacterial colonization specificity and plant growth, but the underlying mechanisms need deepening. An in vitro model, in which E. purpurea axenic plants as host species and E. angustifolia and Nicotiana tabacum as non-host species inoculated with single endophytes isolated from stem/leaf, root and rhizospheric soil, were used to investigate bacterial colonization. Colonization analysis showed that bacteria tended to reach tissues from which they were originally isolated (tissue-specificity) in host plants but not in non-host ones (species-specificity). Primary root elongation inhibition as well as the promotion of the growth of E. purpurea and E. angustifolia plants were observed and related to endophyte-produced indole-3-Acetic Acid. Bacteria-secreted substances affected plant physiology probably interacting with plant regulators. Plant metabolites played an important role in controlling the endophyte growth. The proposed in vitro infection model could be, generally used to identify novel bioactive compounds and/or to select specific endophytes contributing to the host metabolism properties.
TL;DR: Results from this study provide evidences of the involvement of lipid metabolism in the response of ectomycorrhizal plants to water deficit and point to an increased ability to maintain a stable chloroplast membrane functional integrity under stress.
TL;DR: In this article, the authors evaluated the response of wheat plants (Triticum aestivum L.) cultivar Gimeza 7 to various concentrations of foliar application of anti-transpirant substances as kaolin (3 and 6%), potassium sulfate (100 and 200 mg/l), and two pot experiments were conducted during 2016/2017 and 2017/2018 successive growing winter seasons under greenhouse conditions at the Experimental Station, in the National Research Centre, Egypt.
Abstract: Certain substances with some physical and chemical activities can be used to decrease the transpiration rate and alleviate plant water stress through rising leaf resistance to the diffusion of water vapor. Wheat plant is considered as one of the most important and economic winter plants. So, the objective of this work is to evaluate the response of wheat plants (Triticum aestivum L.) cultivar Gimeza 7 to various concentrations of foliar application of anti-transpirant substances as kaolin (3 and 6%), potassium sulfate (100 and 200 mg/l). Two pot experiments were conducted during 2016/2017 and 2017/2018 successive growing winter seasons under greenhouse conditions at the Experimental Station, in the National Research Centre, Egypt. The plants were exposed to various levels of water holding capacity (WHC) 80, 60, and 40%. Water stress led to a decrease in growth parameters, yield components, photosynthetic pigments, and carbohydrate contents as compared to 80% of WHC. Meanwhile, water stress caused significant increases in some compatible solute (total soluble sugar, free amino acids, and proline) and some antioxidant enzymes activities. Foliar treatments of wheat plants with kaolin or K2SO4 led to an increase in growth parameters, yield components, photosynthetic pigments, and carbohydrate constituents. More accumulation of the organic solutes of leaves (total soluble sugar and free amino acids), antioxidant enzyme activities, and some minerals (N, P, K, and Ca) was observed. Data also illustrated that the nutritional values of the grain yield of wheat were also improved when sprayed with kaolin and K2SO4. The used substances are safe for the environment, and for the plant, potassium is an essential nutrient and its ability controls several biochemical and physiological responses in plants. Kaolin also can ameliorate plant physiology and consequently lead to higher yield production.
TL;DR: In this paper, chemical modifications were proposed with the objective of potentializing its biological effects in maize plants, and the derivatives were semi-synthesized (N-succinyl and N,O-dicarboxymethyl) and, together with chitosan, they were applied, via the leaf, in a drought-sensitive maize hybrid (BRS1030) under pre-flowering water deficit.
Abstract: Chitosan induces plant tolerance to various abiotic stresses, including water deficit. However, its use may be limited, due to its constitution and low solubility in water. Thus, chemical modifications were proposed in this study with the objective of potentializing its biological effects in maize plants. The derivatives were semi-synthesized (N-succinyl and N,O-dicarboxymethyl) and, together with chitosan, they were applied, via the leaf, in a drought-sensitive maize hybrid (BRS1030) under pre-flowering water deficit. The water deficit was maintained for 15 days and the analyses were performed at the beginning and end of stress, and also in rehydration. Leaf water potential, gas exchange, chlorophyll fluorescence, and content of chloroplastidic pigments were evaluated. The use of the derivatives modulated photosynthesis parameters, affecting the involved mechanisms, such as stomatal activity, water use efficiency and photosystem II activity. Chlorophyll fluorescence indicated that the antenna complex was damaged by the water deficit condition, with a decrease in the energy flux in the electron transport chain and in the photochemical phase of photosynthesis. However, the spraying of chitosan derivatives induced tolerance to water deficit, suggesting that chitosan derivatives are more bioavailable to plants. Water stress decreases pigment content, but both the application of chitosan and derivatives increased these contents. It is concluded that chitosan derivatives improved the photosynthetic parameters in maize susceptible to drought, inducing tolerance to this stress, and the possible reasons and consequences are discussed.
19 Sep 2019
TL;DR: It is found that hexokinase 1 is needed to turn off photosynthesis in the presence of glucose and for glucose-mediated upregulation of lipid metabolism, and a relatively simple, emerging model system is introduced to investigate conserved eukaryotic sugar sensing and signaling at the base of the green lineage.
Abstract: Global primary production is driven largely by oxygenic photosynthesis, with algae as major contributors. The green alga Chromochloris zofingiensis reversibly switches off photosynthesis in the presence of glucose in the light and augments production of biofuel precursors (triacylglycerols) and the high-value antioxidant astaxanthin. Here we used forward genetics to reveal that this photosynthetic and metabolic switch is mediated by the glycolytic enzyme hexokinase (CzHXK1). In contrast to wild-type, glucose-treated hxk1 mutants do not shut off photosynthesis or accumulate astaxanthin, triacylglycerols, or cytoplasmic lipid droplets. We show that CzHXK1 is critical for the regulation of genes related to photosynthesis, ketocarotenoid synthesis and fatty acid biosynthesis. Sugars play fundamental regulatory roles in gene expression, physiology, metabolism, and growth in plants and animals, and we introduce a relatively simple, emerging model system to investigate conserved eukaryotic sugar sensing and signaling at the base of the green lineage.
TL;DR: The results showed that exposure to Cu and Cr causes decline in plant growth, including biomass and plant height, and suggest that cultivar ZS 758 is more resistant to Cu/Cr than Zheda 622, due to better adapted metabolism and maintenance of structural integrity under metal stress.
Abstract: Nowadays, modern plant physiology focuses on complex behavior of metal co-contaminants in agrosystems. Keeping this in view, the current study was conducted to investigate the response of two Brassica napus cultivars (Zheda 622 and ZS 758) under co-contamination of copper (Cu2+) and chromium (Cr6+) to observe their effects on plant growth, photosynthetic parameters, and subcellular distribution of these metals in leaves and roots. The results showed that exposure to Cu and Cr causes decline in plant growth, including biomass and plant height. Significant decrease in pigment concentration and the photosynthetic activity [photosynthetic rate (Pn), stomatal conductance (Gs), and transpiration rate (E), maximal quantum yield of photosystem II (Fv/Fm)] in leaves was also observed. Results of subcellular distribution of metals showed that Cu and Cr were predominantly distributed in cell wall and soluble fraction of roots and leaves. Moreover, Cu and Cr in cellular fractions showed a synergistic accumulation pattern under combined metal stress treatment. Both cultivars showed increased levels of reactive oxygen species (ROS), i.e., hydrogen peroxide (H2O2) and superoxide radical (O2•-), and significant modulation in the activities of antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX)] under Cu/Cr alone or their combined treatments. Similarly, expression levels of defense-related genes, such as BnCat, BnApx, BnPrx, and BnSod, were also generally up-regulated compared with control. Electron micrographs (TEM) of the mesophyll and root tip cells indicated prominent alterations both in cellular and organelle levels. Additionally, Cr was found to be more toxic than Cu but less than their combined effect, as revealed by enhanced production of oxidative stress and a reduction in biomass production and photosynthetic activity. The present results also suggest that cultivar ZS 758 is more resistant to Cu/Cr than Zheda 622, due to better adapted metabolism and maintenance of structural integrity under metal stress.
TL;DR: The present findings indicate that under drought muskmelon elevates the abundance of defense proteins and suppresses catabolic proteins to counter the impacts of drought induced stress.
Abstract: Water deficiency up to a certain level and duration leads to a stress condition called drought. It is a multi-dimensional stress causing alteration in the physiological, morphological, biochemical, and molecular traits in plants resulting in improper plant growth and development. Drought is one of the major abiotic stresses responsible for loss of crops including muskmelon (Cucumis melo. L). Muskmelon genotype SC-15, which exhibits high drought resistance as reported in our earlier reports, was exposed to deficient water condition and studied for alteration in physiological, molecular and proteomic profile changes in the leaves. Drought stress results in reduced net photosynthetic rate (Pn), stomatal conductance (Gs) and transpiration (E) rate. With expanded severity of drought, declination recorded in content of total chlorophyll and carotenoid while enhancement observed in phenol content indicating generation of oxidative stress. In contrary, activities of catalase (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX), and guaiacol (POD) were increased under drought stress. Peptide mass fingerprinting (PMF) showed that drought increased the relative abundance of 38 spots while decreases10 spots of protein. The identified proteins belong to protein synthesis, photosynthesis, nucleotide biosynthesis, stress response, transcription regulation, metabolism, energy and DNA binding. A drought-induced MADS-box transcription factor was identified. The present findings indicate that under drought muskmelon elevates the abundance of defense proteins and suppresses catabolic proteins. The data obtained exhibits possible mechanisms adopted by muskmelon to counter the impacts of drought induced stress.
TL;DR: Findings suggest that the endophytic fungus CSL-1, which produces IAA and GAs, can play a vital role in promoting plant growth and that C SL-1 could be used to enhance crop growth and mitigate plant stress under a variety of environmental conditions.
Abstract: Endophytic fungi have been considered as strong plant growth promoters due to phytohormones production. The current study reports the isolation of endophytic fungi from bio-prospective medicinal plant cannabis sativa. Endophytic fungus Bipolaris sp. CSL-1 from the leaves of C. sativa was isolated. Culture filtrate (CF) was primarily investigated for indole-3-acetic acid (IAA) and gibberellins (GAs) and was further evaluated for its capability to enhance mutant Waito-C rice growth attributes. A variety of plant growth characteristics, including seedling length, seedling biomass, and chlorophyll content, were significantly promoted by the CF, and the growth-promoting effect was due to IAA and various GAs in the CF. Gas chromatography/mass spectrometry analysis revealed the quantities (ng/mL) of various GAs, including GA1 (0.758 ± 0.005), GA3 (0.00015 ± 0.005), GA4 (0.945 ± 0.081), GA7 (0.6382 ± 0.012), GA9 (0.0125 ± 0.0002), and GA24 (0.0139 ± 0.0013). Similarly, endogenous GA4 (33.243 ± 4.36), GA24 (29.64 ± 2.68), GA7 (22.5 ± 1.3), and GA12 (25.21 ± 2.8) were significantly upregulated in rice mutant after CF application. Furthermore, RT-PCR indicated that IAA and GA pathway genes (des, ggs2, P50-1, P450-4, and iaaH) were expressed in CSL-1 and the combined application of CSL-1 spore suspension with yucasin and uniconazole to maize seedlings revealed that CSL-1 such as exogenous GA3 and IAA alleviated the negative effect of uniconazole and yucasin and promoted maize-seedling growth. These findings suggest that the endophytic fungus CSL-1, which produces IAA and GAs, can play a vital role in promoting plant growth and that CSL-1 could be used to enhance crop growth and mitigate plant stress under a variety of environmental conditions.
TL;DR: Investigation of effects of light quality on tomato fruit sugar metabolism revealed that nine, three, and two proteins related to sugar metabolism were differentially accumulated between the CK and RB31-treated fruit at mature green, breaker, and ripe stages, respectively.
Abstract: Light quality is an important environmental factor that drives photosynthesis and regulates plant growth and development. The purpose of this study was to investigate effects of light quality on sugar metabolism of tomato fruit. Tomato variety ‘Micro-Tom’ was used as the test material. After a 30-day cultivation period, seedlings were moved to an artificial climate chamber and grown under different light conditions: ratio of red and blue light, 1:1 (RB11), ratio of red and blue light, 3:1 (RB31), ratio of red and blue light, 5:1 (RB51), ratio of red and blue light, 7:1 (RB71), and white light as the control (CK). Fruit were harvested at the mature green, breaker, and ripe stages. The soluble sugar, total soluble solids, glucose, fructose, and sucrose contents in developing tomato fruit were highest under the RB31 condition. To further investigate effects of light quality on tomato fruit sugar metabolism, proteomic analysis using total proteins extracted from the CK and RB31-treated tomato fruit revealed that nine, three, and two proteins related to sugar metabolism were differentially accumulated between the CK and RB31-treated fruit at mature green, breaker, and ripe stages, respectively. Seven of them were up-regulated and the rest were down-regulated. The transcript abundances of these corresponding genes were analyzed by qRT-PCR. The expression levels of 12 genes were consistent with the protein abundances, but expression levels of xylose isomerase and l-iditol 2-dehydrogenase did not correlate with their protein abundances.
TL;DR: Overall, TGase positively regulated photosynthesis by maintaining the activation states of the Benson–Calvin cycle and inducing changes in cellular redox homeostasis in tomato.
Abstract: Transglutaminases (TGases), which are widespread cross-linking enzymes in plants, play key roles in photosynthesis and abiotic/biotic stress responses; however, evidence concerning the genetics underlying how TGase improves the capability of photosynthesis and the mechanism of TGase-mediated photosynthesis are not clear in this crop species. In this study, we clarified the function of TGase in the regulation of photosynthesis in tomato by comparing wild-type (WT) plants, tgase mutants generated by the CRISPR/Cas9 system and TGase-overexpressing (TGaseOE) plants. Our results showed that increasing the transcript level of TGase resulted in an enhanced net photosynthetic rate (Pn), whereas the tgase mutants presented significantly inhibited Pns and CO2 assimilation compared with the WT. Although the total RuBisCO activity was not affected by TGase, the initial and activation status of RuBisCO and the activity of RuBisCO activase (RCA) and fructose-1,6-bisphosphatase (FBPase) in TGaseOE plants were significantly higher than that in WT plants. Except for RuBisCO small subunit (RbcS), the transcription levels of Benson-Calvin cycle-related genes were positively related to the endogenous TGase activity. Furthermore, TGaseOE plants had higher protein levels of RuBisCO large subunit (RbcL) and RCA than did WT plants and showed a reduced redox status by enhancing the activity of dehydroascorbate reductase (DHAR) and glutathione reductase (GR), which was compromised in TGase-deficient plants. Overall, TGase positively regulated photosynthesis by maintaining the activation states of the Benson-Calvin cycle and inducing changes in cellular redox homeostasis in tomato.
TL;DR: Even though hydraulics, gas-exchange traits and non-structural carbohydrate pools were negatively affected, coffee trees did not present individual mortality, demonstrating a great resilience to drought events.
Abstract: We analysed field-grown coffee trees that faced the most severe drought event in the last 28 years in Brazil. Vulnerability curves indicated that water potentials were low enough to decrease leaf hydraulic conductance and carbohydrate content under drought. However, individual tree mortality was not observed indicating a great resilience of coffee to drought stress. Drought affects leaf photosynthesis by acting on hydraulic, diffusive and/or biochemical components. Here, we analysed two field-grown coffee (Coffea arabica L.) cultivars (Catuai and Catimor) subjected to a severe natural drought (the most severe drought event in the last 28 years in Brazil) followed by a subsequent rehydration. We estimated leaf hydraulic vulnerability and found that the leaf water potential under drought reached values that were low enough to cause drastic decreases (up to 90%) in leaf hydraulic conductance (Kleaf) in both cultivars. Such Kleaf loss was associated with a reduced stomatal conductance (gs) under drought (c. 70%) and likely limited gas-exchange recovery upon rainfall as abscisic acid levels and gs were not correlated. Net photosynthesis rates (An) were largely limited by diffusive constraints, with gs explaining c. 90% of the variation in An. Rubisco carboxylation capacity and soluble protein content remained unaltered, in contrast to starch content which was drastically reduced by drought. Soluble sugars were less affected, with hexoses having an apparent role as osmolytes. Even though hydraulics, gas-exchange traits and non-structural carbohydrate pools were negatively affected, coffee trees did not present individual mortality, demonstrating a great resilience to drought events.
TL;DR: In this paper, the authors tested the hypothesis that photosynthetic and oxidative changes induced by drought are dependent on CAT activity and obtained results evidence that CO2 assimilation and oxidative protection in leaves of Jatropha curcas plants exposed to water deficit are greatly dependent on drought-induced CAT activity deficiency.
Abstract: Catalase (CAT) is a crucial enzyme to control the excess peroxisomal H2O2 produced during photorespiration. In many plant species, this enzymatic activity decreases in response to drought but its specific role in photosynthesis and redox metabolism is still poorly understood. In this study was tested the hypothesis that photosynthetic and oxidative changes induced by drought are dependent on CAT activity. For this, Jatropha curcas, a drought-tolerant species, was subjected to water deficit and CAT inhibition by a specific pharmacological inhibitor (3-AT), in order to decrease the activity of this enzyme to a similar level as compared to that exhibited by water deficit-treated plants. The CO2 assimilation and other photosynthetic-related parameters were decreased more intensively by drought as compared to plants exposed to 3-AT, whereas the photochemical efficiency of PSII remained unchanged in both conditions. Non-photochemical quenching was strongly increased in drought-treated plants, but only slightly increased in 3-AT treatment. Membrane integrity and lipid peroxidation were strongly increased in both treatments, while H2O2 content was increased only by drought imposition. Ascorbate peroxidase and superoxide dismutase activities were increased in both drought and 3-AT treatments, but glycolate oxidase was strongly increased only in drought-stressed plants. The obtained results evidence that CO2 assimilation and oxidative protection in leaves of Jatropha curcas plants exposed to water deficit are greatly dependent on drought-induced CAT activity deficiency.
TL;DR: In this article, the role of exogenous GSH in improving abiotic stress tolerance in maize was investigated, and the possible physiological mechanism underlying the tolerance phenotypes in GSH-treated plants were also analyzed in this study.
Abstract: The role of exogenous GSH in improving abiotic stress tolerance in maize was investigated in this study. GSH-treated plants showed significantly higher germination percentage, survival rate, plant biomass, and grain yield per plant than control plants. The possible physiological mechanism underlying the tolerance phenotypes in GSH-treated plants were also analyzed in this study. GSH-treated plants showed reduced oxidative destruction, enhanced water retention, and increased activity of antioxidant enzyme, vacuolar H+-pyrophosphatase (V-H+-PPase), and H+-adenosine triphosphatase (V-H+-ATPase), compared to control plants. In addition, the accumulation of abscisic acid (ABA) and the expression of ABA-responsive genes were upregulated by GSH treatment. These results suggested that GSH played a role in relieving oxidative destruction, maintaining plant water content, and promoting higher ABA levels, which were responsible for GSH-enhanced tolerance to abiotic stresses in maize.