ABA Regulation of Plant Responses to Drought and Salt Stresses
01 Jan 2014-pp 315-336
TL;DR: This chapter focuses on the ABA regulation of drought and salt responses in plants, examining gene expression, stress signaling, and ion homeostasis under these stresses.
Abstract: The phytohormone abscisic acid (ABA) plays an essential role in the abiotic stress response and tolerance of plants, especially during water-related stresses. Thus, ABA is also known as a plant stress hormone. In response to drought and/or salinity stresses, the expression of many ABA-responsive genes is16.1 induced. Several transcription factors and their corresponding DNA target sequences have been identified to control this biological response on the molecular level. Drought stress can directly induce ABA biosynthesis, transportation, and release from its storage form. The activity of ion channels, located on the guard cell membrane, is modulated by drought and/or salinity stresses to regulate stomata movement, which can be simulated by treatment with ABA. In this chapter, we focus on the ABA regulation of drought and salt responses in plants, examining gene expression, stress signaling, and ion homeostasis under these stresses.
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TL;DR: Experimental data suggest that SOAR1 likely regulates plant stress responses at least partly by integrating ABA-dependent and independent signaling pathways, which is different from the ABI2/ABI1 type 2C protein phosphatase-mediated ABA signaling.
Abstract: Whereas several mitochondrial/chloroplast pentatricopeptide repeat (PPR) proteins have been reported to regulate plant responses to abiotic stresses, no nucleus-localized PPR protein has been found to play role in these processes. In the present experiment, we provide evidence that a cytosol-nucleus dual-localized PPR protein SOAR1, functioning to negatively regulate abscisic acid (ABA) signaling in seed germination and postgermination growth, is a crucial, positive regulator of plant response to abiotic stresses. Downregulation of SOAR1 expression reduces, but upregulation of SOAR1 expression enhances, ABA sensitivity in ABA-induced promotion of stomatal closure and inhibition of stomatal opening, and plant tolerance to multiple, major abiotic stresses including drought, high salinity and low temperature. Interestingly and importantly, the SOAR1-overexpression lines display strong abilities to tolerate drought, salt and cold stresses, with surprisingly high resistance to salt stress in germination and postgermination growth of seeds that are able to potentially germinate in seawater, while no negative effect on plant growth and development was observed. So, the SOAR1 gene is likely useful for improvement of crops by transgenic manipulation to enhance crop productivity in stressful conditions. Further experimental data suggest that SOAR1 likely regulates plant stress responses at least partly by integrating ABA-dependent and independent signaling pathways, which is different from the ABI2/ABI1 type 2C protein phosphatase-mediated ABA signaling. These findings help to understand highly complicated stress and ABA signalling network.
97 citations
Cites background from "ABA Regulation of Plant Responses t..."
...Plant response to cold stress, like that to drought and salt stresses, requires both ABA-dependent and -independent signaling pathways (Shinozaki et al. 2003; Zhu 2002, 2003; Qin et al. 2011; Ma and Qi 2014; Shi and Yang 2014)....
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TL;DR: It is confirmed that ZDS is encoded by a single gene in tomato transcriptionally regulated by ripening transcription factors RIN, NOR and ethylene and revealed ZDS as an additional bottleneck in ripening‐associated carotenogenesis of tomato.
Abstract: Spontaneous mutations in fruit-specific carotenoid biosynthetic genes of tomato (Solanum lycopersicum) have led to improved understanding of ripening-associated carotenogenesis. Here, we confirm that ZDS is encoded by a single gene in tomato transcriptionally regulated by ripening transcription factors RIN, NOR and ethylene. Manipulation of ZDS was achieved through transgenic repression and heterologous over-expression in tomato. CaMV 35S-driven RNAi repression inhibited carotenoid biosynthesis in all aerial tissues examined resulting in elevated levels of ζ-carotene isomers and upstream carotenoids, while downstream all trans-lycopene and subsequent photoprotective carotenes and xanthophylls were diminished. Consequently, immature fruit displayed photo-bleaching consistent with reduced levels of the photoprotective carotenes and developmental phenotypes related to a reduction in the carotenoid-derived phytohormone abscisic acid (ABA). ZDS-repressed ripe fruit was devoid of the characteristic red carotenoid, all trans-lycopene and displayed brilliant yellow pigmentation due to elevated 9,9' di-cis-ζ-carotene. Over-expression of the Arabidopsis thaliana ZDS (AtZDS) gene bypassed endogenous co-suppression and revealed ZDS as an additional bottleneck in ripening-associated carotenogenesis of tomato. Quantitation of carotenoids in addition to multiple ripening parameters in ZDS-altered lines and ABA-deficient fruit-specific carotenoid mutants was used to separate phenotypic consequences of ABA from other effects of ZDS manipulation and reveal a unique and dynamic ζ-carotene isomer profile in ripe fruit.
42 citations
TL;DR: Measuring relative root growth rate (length) using PEG-treated paper roll-grown seedlings also seems to be a highly suitable and promising method for screening a large number of genotypes in breeding programs.
Abstract: Plant breeders are in the need for a convenient, reproducible, reliable and rapid screening methods to be used as a proxy for drought tolerance for a large number of genotypes. Addressing this need, we compared different physiological measures of stress in six barley (Hordeum vulgare L.) genotypes subjected to different drought treatments under glasshouse conditions. Genotypes were evaluated by measuring transpiration rate, quantum yield of PSII (chlorophyll fluorescence Fv/Fm ratio), SPAD chlorophyll meter reading, dry biomass and shoot water content. The accuracy of different methods for quantifying water stress tolerance was evaluated by measuring the rates of surviving and death in plants and leaves, and newly grown leaves after rewatering. In another experiment, the same genotypes were evaluated by applying 18% (w/v) of polyethylene glycol (PEG) to germinating seeds grown in paper rolls to induce osmotic stress, using relative root and shoot lengths as a measure of tolerance. The results suggest that transpiration measurements at the recovery stage could be the most sensitive method for separating contrasting genotypes. However, the method is time-consuming and laborious for large-scale screening. Chlorophyll content, dry biomass, shoot water content and stomatal density did not correlate with plant drought tolerance. At the same time, chlorophyll fluorescence Fv/Fm ratio showed a strong correlation with drought tolerance and could be recommended as suitable proxy for screening. Measuring relative root growth rate (length) using PEG-treated paper roll-grown seedlings also seems to be a highly suitable and promising method for screening a large number of genotypes in breeding programs.
27 citations
Cites background from "ABA Regulation of Plant Responses t..."
...Under severe drought conditions, stomata respond to chemical signals like ABA, causing stomatal closure and reduced transpiration (Ma and Qin 2014)....
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...drought conditions, stomata respond to chemical signals like ABA, causing stomatal closure and reduced transpiration (Ma and Qin 2014)....
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TL;DR: Significant differences between hybrids grown in low and severe soil compactions and exposed to drought or flooding were noticed in membrane injury, leaf water potential, chlorophyll a content and gas exchange parameters.
Abstract: In field conditions plants undergo combinations of stresses like soil compaction combined with soil drought or flooding. In maize there exists an intraspecific variation in responses to environmental stresses, e.g. drought, flooding and soil compaction. In this study seedlings of two maize hybrids (sensitive and resistant to soil compaction) were grown under low, moderate and high soil compaction levels and drought or flooding. Water potential, electrolyte leakage, chlorophyll a content, gas exchange, ABA and antioxidant activity were measured. In seedlings exposed to different soil compaction levels differences between soil, leaf and root water potentials were observed at noon and later in the day. Significant differences between hybrids grown in low and severe soil compactions and exposed to drought or flooding were noticed in membrane injury, leaf water potential, chlorophyll a content and gas exchange parameters. Statistically significant differences between hybrids were observed in ABA content in the stem under severe and in the root under low soil compaction and exposed to drought and flooding, and in antioxidant activity in leaf under severe soil compaction and under low soil compaction with drought or flooding stresses. Further studies on physiological responses of genotypes contrasting in tolerance to different stresses would help us explore stress tolerance mechanisms.
26 citations
Cites background from "ABA Regulation of Plant Responses t..."
...abiotic stress factors such as drought (Yun and Feng 2014),...
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...ABA, as a key stress hormone, is involved in plants’ reactions to various environmental abiotic stress factors such as drought (Yun and Feng 2014), soil compaction and flooding stress (Jackson 2002)....
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...On the other hand, there is no clear information on ABA synthesis depending on the current state of hydration and on cytoplasmic membrane damages caused by these factors (Else et al. 2009; Jackson 2002; Janowiak et al. 2002; Saniewski et al. 2003; Yun and Feng 2014)....
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TL;DR: Abscisic acid (ABA) is a stress phytohormone as a signaling molecule that led to investigate its potential to improve morpho-physiological characteristics, antioxidant metabolism, and ion homeostasis in wheat (Triticum aestivum L.) seedlings grown under salinity stress (0, 50, and 100mM NaCl) as mentioned in this paper.
Abstract: Salinity, one of the catastrophic abiotic stresses that uces wheat production around the globe. Abscisic acid (ABA) is a stress phytohormone as a signaling molecule that led us to investigate its potential to improve morpho-physiological characteristics, antioxidant metabolism, and ion homeostasis in wheat (Triticum aestivum L.) seedlings grown under salinity stress (0, 50, and 100 mM NaCl). The findings suggested that salt-induced toxicity significantly (P + ion accumulation and uptake in wheat leaf and root tissues with the increasing NaCl concentration in the nutrient media. However, root-zone supply of ABA (0, 5, and 10 μ M) prominently alleviated salt induced phytotoxicity. The 10 μ M concentration of ABA promoted shoot (81.7%) and root (102.1%) dry weight, root length (38.2%), Chl. a (65.3%), Chl. b (149.0%), carotenoids (95.7%) and membrane damage (36.7%) when NaCl was added at 100 mM, relative to the corresponding treatment without ABA. Moreover, ABA (10 μ M) supply decreased Na + ion uptake (root to leaf) due to reduced transpiration rate (81.1%), and thereby ameliorated oxidative injury by ucing leaf malondialdehyde (MDA) and H 2 O2 contents by 36.8% and 29.9%, respectively, at 100 mM NaCl stress, relative to the similar treatment without ABA. In addition, the activities of catalase (CAT), superoxide dismutase (SOD), and ascorbate peroxidase (APX) were upregulated by 143.9%, 20.2%, and 19.5% in leaves and by 144.9%, 23.4% and 41.1% in roots respectively, with 10 μ M ABA application under 100 mM salinity stress, compa to the 100 mM NaCl treatment without ABA. Conclusively, this study proposed that root-zone ABA application promoted salinity tolerance in wheat seedlings and could be a practical approach for wheat production in salt-affected regions to ensure food security.
25 citations
References
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TL;DR: Salt and drought stress signal transduction consists of ionic and osmotic homeostasis signaling pathways, detoxification (i.e., damage control and repair) response pathways, and pathways for growth regulation.
Abstract: Salt and drought stress signal transduction consists of ionic and osmotic homeostasis signaling pathways, detoxification (i.e., damage control and repair) response pathways, and pathways for growth regulation. The ionic aspect of salt stress is signaled via the SOS pathway where a calcium-responsive SOS3-SOS2 protein kinase complex controls the expression and activity of ion transporters such as SOS1. Osmotic stress activates several protein kinases including mitogen-activated kinases, which may mediate osmotic homeostasis and/or detoxification responses. A number of phospholipid systems are activated by osmotic stress, generating a diverse array of messenger molecules, some of which may function upstream of the osmotic stress-activated protein kinases. Abscisic acid biosynthesis is regulated by osmotic stress at multiple steps. Both ABA-dependent and -independent osmotic stress signaling first modify constitutively expressed transcription factors, leading to the expression of early response transcriptional activators, which then activate downstream stress tolerance effector genes.
5,328 citations
TL;DR: The elucidation ofMYB protein function and regulation that is possible in Arabidopsis will provide the foundation for predicting the contributions of MYB proteins to the biology of plants in general.
3,542 citations
Book•
01 Jan 2002
TL;DR: This edition of Biochemistry & Molecular Biology of Plants holds a unique place in the plant sciences literature as it provides the only comprehensive, authoritative, integrated single volume book in this essential field of study.
Abstract: Since its publication in 2000, Biochemistry & Molecular Biology of Plants, has been hailed as a major contribution to the plant sciences literature and critical acclaim has been matched by global sales success. Maintaining the scope and focus of the first edition, the second will provide a major update, include much new material and reorganise some chapters to further improve the presentation. This book is meticulously organised and richly illustrated, having over 1,000 full-colour illustrations and 500 photographs. It is divided into five parts covering: Compartments: Cell Reproduction: Energy Flow; Metabolic and Developmental Integration; and Plant Environment and Agriculture. Specific changes to this edition include: Completely revised with over half of the chapters having a major rewrite. Includes two new chapters on signal transduction and responses to pathogens. Restructuring of section on cell reproduction for improved presentation. Dedicated website to include all illustrative material. Biochemistry & Molecular Biology of Plants holds a unique place in the plant sciences literature as it provides the only comprehensive, authoritative, integrated single volume book in this essential field of study.
3,439 citations
TL;DR: Overexpression of the DREB1A cDNA in transgenic Arabidopsis plants not only induced strong expression of the target genes under unstressed conditions but also caused dwarfed phenotypes in the transgenic plants, and revealed freezing and dehydration tolerance.
Abstract: Plant growth is greatly affected by drought and low temperature. Expression of a number of genes is induced by both drought and low temperature, although these stresses are quite different. Previous experiments have established that a cis-acting element named DRE (for dehydration-responsive element) plays an important role in both dehydration- and low-temperature-induced gene expression in Arabidopsis. Two cDNA clones that encode DRE binding proteins, DREB1A and DREB2A, were isolated by using the yeast one-hybrid screening technique. The two cDNA libraries were prepared from dehydrated and cold-treated rosette plants, respectively. The deduced amino acid sequences of DREB1A and DREB2A showed no significant sequence similarity, except in the conserved DNA binding domains found in the EREBP and APETALA2 proteins that function in ethylene-responsive expression and floral morphogenesis, respectively. Both the DREB1A and DREB2A proteins specifically bound to the DRE sequence in vitro and activated the transcription of the b-glucuronidase reporter gene driven by the DRE sequence in Arabidopsis leaf protoplasts. Expression of the DREB1A gene and its two homologs was induced by low-temperature stress, whereas expression of the DREB2A gene and its single homolog was induced by dehydration. Overexpression of the DREB1A cDNA in transgenic Arabidopsis plants not only induced strong expression of the target genes under unstressed conditions but also caused dwarfed phenotypes in the transgenic plants. These transgenic plants also revealed freezing and dehydration tolerance. In contrast, overexpression of the DREB2A cDNA induced weak expression of the target genes under unstressed conditions and caused growth retardation of the transgenic plants. These results indicate that two independent families of DREB proteins, DREB1 and DREB2, function as trans-acting factors in two separate signal transduction pathways under low-temperature and dehydration conditions, respectively.
2,886 citations
TL;DR: PYR/PYLs are ABA receptors functioning at the apex of a negative regulatory pathway that controls ABA signaling by inhibiting PP2Cs, illustrating the power of the chemical genetic approach for sidestepping genetic redundancy.
Abstract: Type 2C protein phosphatases (PP2Cs) are vitally involved in abscisic acid (ABA) signaling. Here, we show that a synthetic growth inhibitor called pyrabactin functions as a selective ABA agonist. Pyrabactin acts through PYRABACTIN RESISTANCE 1 (PYR1), the founding member of a family of START proteins called PYR/PYLs, which are necessary for both pyrabactin and ABA signaling in vivo. We show that ABA binds to PYR1, which in turn binds to and inhibits PP2Cs. We conclude that PYR/PYLs are ABA receptors functioning at the apex of a negative regulatory pathway that controls ABA signaling by inhibiting PP2Cs. Our results illustrate the power of the chemical genetic approach for sidestepping genetic redundancy.
2,336 citations