Showing papers in "Plant and Cell Physiology in 1996"
TL;DR: In transgenic tobacco plants, a representative powerful promoter, as compared to the 35S promoter, allowed 10- and 50-fold higher levels of expression on average and at most, respectively, with no clear qualitative differences in tissue- and organ-specific patterns of expression.
Abstract: A series of chimeric promoters for higher-level expression of foreign genes in plants was constructed as fusions of a gene for beta-glucuronidase (GUS) with the terminator of a gene for nopaline synthase (nos) or of the cauliflower mosaic virus (CaMV) 35S transcript, and the strength of these promoters was assayed in transient and stable expression systems in tobacco and rice. As parts of these promoters, the CaMV 35S core promoter, three different 5'-upstream sequences of the 35S promoter, the first intron of a gene for phaseolin, and a 5'-untranslated sequence (omega sequence) of tobacco mosaic virus were used in various combinations. In tobacco and rice protoplasts, all three fragments of the 35S promoter (-419 to -90, -390 to -90 and -290 to -90, relative to the site of initiation of transcription), the intron, and the omega sequence effectively enhanced GUS activity. Some chimeric promoters allowed levels of GUS activity that were 20- to 70-fold higher than those obtained with the 35S promoter in pBI221. In tobacco protoplasts, the two longer fragments of the 35S promoter were more effective than the shortest fragment. In rice cells, by contrast, the shortest fragment was as effective as the two longer ones. The terminator of the 35S transcript was more effective than that of the nos gene for gene expression. In transgenic tobacco plants, a representative powerful promoter, as compared to the 35S promoter, allowed 10- and 50-fold higher levels of expression on average and at most, respectively, with no clear qualitative differences in tissue- and organ-specific patterns of expression. When the representative promoter was introduced into tobacco with a gene for luciferase, the autofluorescence of detached leaves after a supply of luciferin to petioles was great and was easily detectable by the naked eye in a dark room.
602 citations
TL;DR: It is suggested that only Gramineae plants might contain the eukaryotic ACCases both in the plastids and in the cytosol, as the first possible example of substitution of a plastid gene by a nuclear gene for a non-ribosomal component.
Abstract: The presence and the absence of a prokaryote type and a eukaryote type of acetyl-CoA carboxylase (EC 6.4.1.2; ACCase) were examined in members of 28 plant families by two distinct methods: the detection of biotinylated subunits of ACCase with a streptavidin probe, and the detection of the accD gene, which encodes a subunit of the prokaryotic ACCase, by Southern hybridization analysis. The protein extracts of all the plants studied contained a biotinylated polypeptide of 220 kDa, which was probably the eukaryotic ACCase. All the plants but those belonging to Gramineae also contained a biotinylated polypeptide of ca. 35 kDa, which is a putative subunit of the prokaryotic ACCase. In all plants but those in Gramineae, the ca. 35 kDa polypeptide was found in the protein extracts of plastids, while the 220 kDa polypeptide was absent from these plastid extracts. The plastid extracts of the plants in Gramineae contained the 220 kDa polypeptide, as did the homogenates of the leaves. Southern hybridization analysis demonstrated that all the plants but those in the Gramineae contained the accD gene. These findings suggest that most higher plants have the prokaryotic ACCase in the plastids and the eukaryotic ACCase in the cytosol. Only Gramineae plants might contain the eukaryotic ACCases both in the plastids and in the cytosol. The origin of the plastid-located eukaryotic ACCase in Gramineae is discussed as the first possible example of substitution of a plastid gene by a nuclear gene for a non-ribosomal component.
273 citations
TL;DR: A novel type of photoinhibition has recently been characterized in chillingsensitive plants and occurs under relatively weak illumination at chilling temperatures and the main site of damage is in PSI.
Abstract: Photoinhibition was denned originally as the decrease in photosynthetic activity that occurs upon excess illumination The site of photoinhibiti on has generally been considered to be located in PSII However, a novel type of photoinhibition has recently been characterized in chillingsensitive plants This photoinhibition occurs under relatively weak illumination at chilling temperatures and the main site of damage is in PSI The photoinhibition of PSI is initiated by the inactivation of the acceptor side, with the subsequent destruction of the reaction center and the degradation of the product of the psaB gene, which is one of the two major subunit polypeptides of the PSI reaction center complex Chilling and oxidative stress (the presence of reactive species of oxygen) are characteristic requirements for the photoinhibition of PSI in vivo
252 citations
TL;DR: Treatment of potato tuber tissues with l-hydroxy-2-oxo-3,3-bis(2-aminoethyl)1-triazene (NOC-18), an NO-releasing compound, induced the accumulation of the potato phytoalexin rishitin, suggesting a phytochemical inducing activity for NO.
Abstract: We investigated whether nitric oxide (NO) radical could induce phytoalexin production. Treatment of potato tuber tissues with 1-hydroxy-2-oxo-3,3-bis(2-aminoethyl)1-triazene (NOC-18), an NO-releasing compound, induced the accumulation of the potato phytoalexin rishitin. This induction was inhibited by carboxy-2-phenyl-4,4,5,5-tetramethylimidazoline 1-oxyl-3-oxide (carboxy-PTI0), an NO-specific scavenger, or by Tiron, a radical scavenger, suggesting a phytoalexin inducing activity for NO.
210 citations
TL;DR: The findings suggest that the PBZ1 gene has an important function during the disease resistance response in rice, and significant homology at the amino acid level exists between the predictedPBZ1 protein and intracellular pathogenesis-related (IPR) proteins.
Abstract: Probenazole (3-allyloxy-1,2-benzisothiazole-1,1-dioxide) induces disease resistance in rice against rice blast fungus. To investigate the molecular mechanism of probenazole-induced resistance, we isolated and characterized a cDNA clone of a probenazole-inducible gene in rice, which encoded a protein designated PBZ1. Sequence analysis revealed that significant homology at the amino acid level exists between the predicted PBZ1 protein and intracellular pathogenesis-related (IPR) proteins. Accumulation of PBZ1 mRNA was not induced by wounding, but markedly induced by inoculation with rice blast fungus. In addition, it was induced sooner by inoculation with an incompatible race than that with a compatible race. On the other hand, when the accumulation of the PBZ1 mRNA was examined after treatment with probenazole-related compounds, it was not fully correlated with anti-rice blast activity. However, it was induced after treatment with N-cyano-methyl-2-chloro-isonicotinamide (NCI), which belongs to another group of compounds known to induce disease resistance. Thus, although the accumulation of the PBZ1 mRNA was not fully correlated with anti-rice blast activity, our findings suggest that the PBZ1 gene has an important function during the disease resistance response in rice.
200 citations
TL;DR: A similar degree of photoinhibition occurred under excess visible light in the red versus green varieties; whereas, the red leaf varieties were less damaged by UV-B and UV-C radiation suggesting protection by anthocyanin in their epidermal tissue.
Abstract: The maximum quantum yield for photosynthetic O2 evolution in red leaf coleus varieties having anthocyanin in their upper epidermis is much lower in green light and slightly lower in white light than in a green leaf variety lacking anthocyanin. A similar degree of photoinhibition occurred under excess visible light in the red versus green varieties; whereas, the red leaf varieties were less damaged by UV-B and UV-C radiation suggesting protection by anthocyanin in their epidermal tissue.
198 citations
TL;DR: Root growth of barley was inhibited by 200 raM NaCl, when 1 mM CaCl2 was present in the hydroponic culture solution, and nuclear degradation was accompanied by apoptosislike DNA fragmentation.
Abstract: Root growth of barley (Hordeum vulgare L., cv. Akashinriki) was inhibited by 200 raM NaCl, when 1 mM CaCl2 was present in the hydroponic culture solution. Increasing the CaCl2 up to 10 mM partially prevented this inhibition. However, inhibition also occurred with 100 mM NaCl in the presence of 0.1 mM CaCI 2. The nuclei of meristematic cells in roots in which growth had been inhibited by salt stress were studied after staining with DAPI (4',6-diamino-2-phenyIindol). Nuclear deformation of the cells occurred with 12 h of salt stress with 500 mM NaCl, and was followed by degradation. The nuclear degradation was also observed when the roots were exposed to more than 300 mM NaCl for 24 h. Biochemical analysis revealed that nuclear degradation was accompanied by apoptosislike DNA fragmentation. The intracellular mechanisms of nuclear degradation in cells after salt stress are discussed.
177 citations
TL;DR: Natural photosynthesis is discovered using Zn-containing bacteriochlorophyll a in an acidophilic bacterium Addiphilium rubrum, indicating an unexpectedly wide variability of photosynthesi s.f.
Abstract: We discovered natural photosynthesis using Zn-containing bacteriochlorophyll a in an acidophilic bacterium Addiphilium rubrum. Chemical analysis of the cell extracts gave a 13 : 2 :1 molar ratio of Zn-bacterioch lorophyll a : Mg-bacteriochlorophyll a : bacteriopheophytin a. Most of the pigments are associated with fully active reaction center and light-harvesting complexes analogous to those in purple photosynthetic bacteria. The finding indicates an unexpectedly wide variability of photosynthesi s.
174 citations
TL;DR: Observations suggest that hydrogen peroxide at nanomolar levels, produced by autooxidation of ascorbate at lower than micromolar Levels, might participate in the inactivation of tAPX.
Abstract: One of the characteristic properties of ascorbate peroxidase (APX), which distinguishes it from guaiacol peroxidase, Cyt c peroxidase and glutathione peroxidase, is the rapid inactivation of the enzyme under conditions where an electron donor is absent. When thylakoid-bound APX (tAPX) in 100 f/M ascorbate was diluted 500-fold with an ascorbate-depleted medium, the enzymatic activity was lost with half time of about 15 s. The inactivation of tAPX was suppressed under anaerobic conditions and also by the addition of catalase, but it was unaffected by the addition of superoxide dismutase. These observations suggest that hydrogen peroxide at nanomolar levels, produced by autooxidation of ascorbate at lower than micromolar levels, might participate in the inactivation of tAPX. The participation of hydrogen peroxide was confirmed by the inactivation of tAPX upon incubation with hydrogen peroxide under anaerobic conditions. In the absence of ascorbate, the heme of the two-electron-oxidized intermediate of tAPX (designated Compound I) is decomposed by hydrogen peroxide. Thus, the instability of Compound I to hydrogen peroxide is responsible for the inactivation of APX when ascorbate is not available for Compound I and the enzyme cannot turnover.
173 citations
TL;DR: The introduction of chimeric sense and antisense gene constructs for 4-coumarate:coenzyme A ligase into tobacco plants caused the reduction of the 4CL activity in the transgenic plants, indicating that 4CL has important roles in the determination of the composition and the amount of lignin in tobacco plants.
Abstract: The introduction of chimeric sense and antisense gene constructs for 4-coumarate:coenzyme A ligase into tobacco plants caused the reduction of the 4CL activity in the transgenic plants. In the transgenic plants, the cell walls of the xylem tissue in stems were brown and the molecular structure of lignin in the colored cell walls was dramatically different from that in the control plants. Analysis with different types of stain revealed that levels of cinnamyl aldehyde residues and syringyl units in lignin were depressed in the brownish cell walls. Furthermore, the lignin content in colored tissue was lower than that in the normal tissue. Our results indicate that 4CL has important roles in the determination of the composition and the amount of lignin in tobacco plants.
160 citations
TL;DR: In 15 species it seemed likely that RG-II might be the exclusive carrier of boron in the cell wall, and in all the species examined, cell-wall borons was judged to be associated withRG-II.
Abstract: The presence of a borate-rhamnogalacturonan II (RGII) complex [Kobayashi et al. (1996) Plant Physiol. 110: 1017] was examined in cell walls of 24 species from higher plants. We studied two species in Brassicaceae, three in Cucurbitaceae, four in Leguminosae, two in Apiaceae, two in Chenopodiaceae, two in Solanaceae, two in Asteraceae, one in Liliaceae, one in Araeae, two in Amaryllidaceae and three in Gramineae. In all the species examined, cell-wall boron was judged to be associated with RG-II. Moreover, in 15 species it seemed likely that RG-II might be the exclusive carrier of boron in the cell wall.
TL;DR: Full length cDNA clones of flavonoids 3',5'-hydroxylase, dihydroflavonol 4-reductase and flavonoid 3-glucosyltransferase were cloned from petals of Gentiana triflora and enzymatically characterized by expressing cDNAs in heterologous expression systems.
Abstract: Full length cDNA clones of flavonoid 3',5'-hydroxylase, dihydroflavonol 4-reductase and flavonoid 3-glucosyltransferase were cloned from petals of Gentiana triflora. Their sequences were homologous to counterparts from other plants. Flavonoid 3',5'-hydroxylase and flavonoid 3-glucosyltransferase were enzymatically characterized by expressing cDNAs in heterologous expression systems.
TL;DR: The identification of genes for the reduction of Pchlide provides the groundwork for investigations of the mechanism that regulates the synthesis of Chl, which is closely coordinated with greening in plants.
Abstract: The reduction of Protochlorophyllide (Pchlide) is a major regulatory step in the biosynthesis of chlorophyll (Chl) in oxygenic phototrophs Two different enzymes catalyze this reduction: a light-dependent enzyme (LPOR), which is unique as a consequences of its direct utilization of light for catalysis; and a light-independent Pchlide reductase (DPOR) Since the reduction of Pchlide in angiosperms is catalyzed exclusively by LPOR, they become etiolated in the absence of light LPOR, a major protein in etioplast membranes, consists of a single polypeptide and it exists as a ternary complex with its substrates, Pchlide and NADPH By contrast to the copious information about LPOR, limited information about DPOR has been reported Recent molecular genetic analyses in a cyano-bacterium and a green alga have revealed that at least the three genes, namely, chlL, chlN and chlB, encode proteins essential for the activity of DPOR These genes are widely distributed among phototrophic organisms with exception of angiosperms and Euglenophyta This distribution seems to be well correlated with light-independent greening ability These genes might have been lost during the evolution of gymnosperms to angiosperms The similarities among the deduced amino acid sequences of the three gene products and the subunits of nitrogenase suggest an evolutionary relationship between DPOR and nitrogenase The identification of genes for the reduction of Pchlide provides the groundwork for investigations of the mechanism that regulates the synthesis of Chl, which is closely coordinated with greening in plants
TL;DR: Because transgenic plants constitutively produce four- to six-fold higher amounts of endogenous cytokinin than wild-type plants, it is concluded that cytokinins are indispensable for control of endogenous levels of SA and JA.
Abstract: Plants respond differentially to wounding and pathogens using distinct signaling pathways, so that wound signals are transmitted to jasmonic acid (JA) which induces basic pathogenesis-related (PR) proteins, whereas pathogenic signals cause, in addition to JA, accumulation of salicylic acid (SA) which stimulates production of acidic PR proteins. Transgenic tobacco plants expressing a gene for a small GTP binding protein respond abnormally to mechanical wounding to produce SA and consequently acidic PR proteins, suggesting that wound signals cross witli pathogen signaling pathways [Sano et al. (1994) Proc. Natl. Acad. Sci. USA 91: 10556]. This unusual signal crossing is associated with a highly sensitive wound-response of transgenic plants which, upon wounding, produce JA at least eighteen hours earlier than wild-type plants. When wildtype plants are wounded in the presence of the synthetic cytokinin, benzylaminopurine, production of JA begins six hours earlier than in untreated samples, and also SA begins to accumulate. The cytokinin antagonist, 2-chloro-4-cyclohexylamino-6-ethylamino-s-triazine, erases these effects. Because transgenic plants constitutively produce four- to six-fold higher amounts of endogenous cytokinins than wild-type plants, it is concluded that cytokinins are indispensable for control of endogenous levels of SA and JA.
TL;DR: It is demonstrated that the background level of ethylene intensifies the effects of auxin transport inhibitors, and that NPA-resistant mutants of Arabidopsis thaliana, with mutations designated pir1 and pir2, that were also resistant to TIBA, have a weak auxin-like inhibitory effect.
Abstract: Polar auxin transport inhibitors, including TV-1-naphthylphthalamic acid (NPA) and 2,3,5-triiodobenzoic acid (TIBA), have various effects on physiological and developmental events, such as the elongation and tropism of roots and stems, in higher plants. We isolated NPA-resistant mutants of Arabidopsis thaliana, with mutations designated pirl and pir2, that were also resistant to TIBA. The mutations specifically affected the root-elongation process, and they were shown ultimately to be allelic to auxl and ein2, respectively, which are known as mutations that affect responses to phytohormones . The mechanism of action of auxin transport inhibitors was investigated with these mutants, in relation to the effects of ethylene, auxin, and the polar transport of auxin. With respect to the inhibition of root elongation in A. thaliana, we demonstrated that (1) the background level of ethylene intensifies the effects of auxin transport inhibitors, (2) auxin transport inhibitors might act also via an inhibitory pathway that does not involve ethylene, auxin, or the polar transport of auxin, (3) the hypothesis that the inhibitory effect of NPA on root elongation is due to high-level accumulation of auxin as a result of blockage of auxin transport is not applicable to A. thaliana, and (4) in contrast to NPA, TIBA itself has a weak auxin-like inhibitory effect.
TL;DR: The PLA2 activity of the patatin was much higher than the PLA1 activity, even though the protein exhibited both activities, and was particularly apparent when phosphatidylcholine with linoleic acid at the sn-2 position was used as substrate.
Abstract: Phospholipase (PL) A2is involved in signal transduction in the resistance reaction that is induced in potato by inoculation of an incompatible race of Phytophthora infestans, the late blight fungus, or by treatment with fungal elicitor hyphal wall components (Kawakita et al. 1993). In this study, PLA2 in the soluble fraction from potato tuber was purified. The following results suggested that the enzyme was, in fact, patatin: (1) the molecular mass of the purified enzyme was 40 kDa, the same as that of patatin; (2) the pi of the purified enzyme was approximately 4.75, which corresponds to that of patatin; and (3) the amino-terminal amino acid sequence of the purified enzyme showed a high degree of homology to that of patatin. Patatin is known as a storage protein of the potato tuber and it has been shown to have esterase activity. However, other enzymatic activities and the function(s) of patatin are unknown. We investigated the PLA activities of the purified patatin. The PLA2 activity of the patatin was much higher than the PLA, activity, even though the protein exhibited both activities. The PLA2 activity of the enzyme was particularly apparent when phosphatidylcholine with linoleic acid at the sn-2 position was used as substrate. Lower activity was observed with phosphatidylcholine with palmitic acid, oleic acid and arachidonic acid at the sn-2 position.
TL;DR: The results suggest that the ethylene-induced expression of OLP is regulated by a trans-acting factor(s) common to basic PR-proteins.
Abstract: Osmotin-like protein (OLP) is a neutral isoform in the group 5 pathogenesis-related (PR) tobacco proteins. The OLP gene, like the basic PR protein genes, is constitutively expressed in tobacco roots and cultured cells. OLP is not naturally present in intact healthy leaves, but ethylene treatment induces a high accumulation there. To study the mechanism of OLP gene expression as induced by ethylene, we cloned the gene from Nicotiana sylvestris, an ancestor of N. tabacum. Sequence analysis showed that it has no intron and that its promoter region contains two AGCCGCC sequences that are conserved in most basic PR-protein genes. The function of the AGCCGCC sequences in transgenic tobacco plants that harbor the wild and mutated OLP promoter::GUS fusion genes was analyzed. Mutation in the AGCCGCC sequences clearly inhibited the GUS expression induced by ethylene, indicative that the AGCCGCC sequence(s) is a DNA element(s) responsive to ethylene. An EREBP2 protein, isolated as one of the proteins binding to the AGCCGCC sequence of the tobacco beta-1,3-glucanase gene, also was found to bind to the AGCCGCC sequence(s) of OLP gene. These results suggest that the ethylene-induced expression of OLP is regulated by a trans-acting factor(s) common to basic PR-proteins.
TL;DR: An index, 'nitrogen deficit (ND*)', was introduced, to quantify nitrogen deficit of the whole plant, and the decrease in leaf N was expressed as a liner function of ND* irrespective of the growth conditions, which indicates validity of this index.
Abstract: We examined changes in nitrogen content of the first leaves in relation to growth and nitrogen status of sunflower (Helianthus annuus L.) plants that were raised hydroponically at two irradiance levels (high and low light, HL and LL) and at two nitrogen concentrations (high and low nitrogen, HN and LN). Initial increases in total dry mass and total nitrogen of the whole plant were faster in HL-plants than in LL-plants irrespective of nitrogen supply, but in LN-plants the increase in total nitrogen was soon blunted. When plants grown under the same irradiance were compared, nitrogen content of the first leaves (leaf N) decreased faster in LN-plants than in HN-plants, while for the plants grown at the same nitrogen concentrations, it decreased faster in HL-plants than in LL-plants. Since these changes in leaf N were not explained solely by the changes in plant dry mass or plant nitrogen, we introduced an index, 'nitrogen deficit (ND*)', to quantify nitrogen deficit of the whole plant. ND* was expressed as ND*(t) = [NmM— N(t)] x DM(t), where Nmax and N(t) were nitrogen contents in the young, expanding leaves that had just unfolded to expand, at the initial stage with sufficient nitrogen and at time t, respectively, and DM(t), plant dry mass at t. The decrease in leaf N was expressed as a liner function of ND* irrespective of the growth conditions, which indicates validity of this index. Limitation of the use of ND*, and mechanisms by which leaves sense nitrogen demand are also discussed.
TL;DR: The light-dependent production of hydroxyl radicals by thylakoids, chloroplasts and leaves of Spinacia oleracea was investigated using dimethylsulfoxide as HO' trapping agent and methylviologen decreased HO* formation in the absence, but stimulated it in the presence of Fe 3+.
Abstract: The light-dependent production of hydroxyl radicals (HO*) by thylakoids, chloroplasts and leaves of Spinacia oleracea was investigated using dimethylsulfoxide as HO' trapping agent. Maximum rates of HO' production by thylakoids as indicated by the formation of methane sulfinic acid were observed under aerobic conditions in the absence of added electron acceptors. They were higher than 2 /anol (mgChlh)"1. Saturation of HO* production occurred at the low photon flux density of 100 /rniol m~2 s"1. Trapping of HO* by dimethylsulfoxide suppressed, but did not eliminate light-dependent inactivation of PSI and II suggesting that HO' formation contributed to the photosensitivity of isolated thylakoids. DCMU inhibited HO' formation. Importantly, methylviologen decreased HO* formation in the absence, but stimulated it in the presence of Fe 3+. In intact chloroplasts, HO' formation became appreciable only after KCN had been added to inhibit effective H2O2 scavenging by ascorbate peroxidase. It was stimulated by ferrisulfate, but not by ferricyanide which does not penetrate the chloroplast envelope. Infiltrated spinach leaves behaved similar in principle to intact chloroplasts in regard to HO* formation but HO' production was very slow if detectable at all by the formation of methylsulfini c acid indicating effective radical detoxification. HO' formation is interpreted to be the result of a Fenton-type reaction which produces HO' in chloroplasts from H2O2 and reduced ferredoxin, when O2 is electron acceptor in the Mehler reaction and radical detoxification reactions are inhibited.
TL;DR: Sequence analysis of CPRD8 and CPRD22 cDNAs revealed that they encoded putative proteins that were related to old yellow enzyme and group 2 LEA proteins, respectively, which indicates the existence of at least two signal-transduction pathways between the detection of water stress and the expression of CPRd genes in cowpea.
Abstract: Ten cDNAs of genes that were induced by dehydration stress were cloned by differential screening from the highly drought-tolerant legume, cowpea (Vigna unguiculata), a major crop in West Africa. The clones were collectively named CPRD (cowpea clones responsive to dehydration). Northern blot analysis revealed that nine of the CPRD genes were induced by dehydration stress, but the timing of induction of mRNA synthesis varied among the CPRD genes. We analyzed the effects of other environmental stresses on the expression of the CPRD8, CPRD14 and CPRD22 genes, and we found that these genes were strongly induced by high-salinity stress but not by cold or heat stress. Drought-stressed cowpea plants accumulated abscisic acid (ABA) to a level that was 160 times higher than that in unstressed plants. The CPRD8 and CPRD22 genes were induced to a significant extent by the application of exogenous ABA but the CPRD14 gene was not. These results indicate the existence of at least two signal-transduction pathways between the detection of water stress and the expression of CPRD genes in cowpea. Sequence analysis of CPRD8 and CPRD22 cDNAs revealed that they encoded putative proteins that were related to old yellow enzyme and group 2 LEA proteins, respectively. The protein encoded by CPRD14 exhibited sequence homology to dihydroflavonol-4-reductase (DFR) and vestitone reductase (VR). Old yellow enzyme, DFR and VR have not been identified as drought-inducible proteins in other plants, whereas LEA genes have been well characterized as drought-inducible genes. The various gene products might function to protect cells from environmental stress.
TL;DR: The results indicate that ndh genes may be involved in the protection of chloroplasts against photooxidative stress, particularly in mature-senescent leaves.
Abstract: A 76 amino acid sequence of NDH-A (the protein encoded by plastid ndhA gene) from barley (Hordeum vulgare L.) was expressed as a fusion protein with beta-galactosidase in E. coli. The corresponding antibody generated in rabbits was used to investigate localization, expression and synthesis in vitro of NDH-A. NDH-A was identified as a 35 kDa polypeptide localized in thylakoid membrane. Western blots shows a large increase in NDH-A levels when barley leaves were incubated under photooxidative conditions, which was more pronounced in mature-senescent leaves than in young leaves. Immunoprecipitation of the [35S]methionine labelled proteins, synthesized in vitro by isolated chloroplasts, demonstrated the synthesis in chloroplasts of the NDH-A 35 kDa polypeptide when barley leaves had been incubated under photooxidative conditions. The results indicate that ndh genes may be involved in the protection of chloroplasts against photooxidative stress, particularly in mature-senescent leaves.
TL;DR: The occurrence of new isoforms of Jip-23 during germination in comparison to jasmonate-treated leaves suggests, that the JIP-23 gene family of barley is able to express different subsets of isoforms dependent on the developmental stage.
Abstract: Developmental expression of a 23 kDa jasmonate-induced protein (JIP-23) of barley leaves (Hordeum vulgare cv. Salome) was studied by measuring the time-dependent accumulation of transcript and protein during germination. Tissue-specific expression of JIP-23 was analyzed immunocytochemically and by in situ hybridizations, respectively. During seed germination JIP-23 mRNA was found to accumulate transiently with a maximum at 32 h, whereas the protein was steadily detectable after the onset of expression. The occurrence of new isoforms of JIP-23 during germination in comparison to jasmonate-treated leaves suggests, that the JIP-23 gene family of barley is able to express different subsets of isoforms dependent on the developmental stage. JIP-23 and its transcript were found mainly in the scutellum, the scutellar nodule and in lower parts of the primary leaf of 6 days old seedings. All these tissues exhibited high levels of endogenous jasmonates. In situ hybridization revealed specific accumulation of JIP-23 mRNA in companion cells of the phloem in the nodule plate of the scutellum. In accordance with that, JIP-23 was detected immunocytochemically in phloem cells of the root as well as of the scutellar nodule and in parenchymatic cells of the scutellum. The cell type-specific occurrence of JIP-23 was restricted to cells, which are known to be highly stressed osmotically by active solute transport. This observation suggests, that the expression of this protein might be a response to osmotic stress during development.
TL;DR: It is proposed that acetate-induced stimulation of the chlororespiratory electron flow triggers the regulation of PSII.
Abstract: Addition of acetate to a suspension of Chlamydomonas reinhardtii cells in darkness induced transient and biphasic non-photochemical quenching of Chi fluorescence (qN) due to -dpH-dependen t down-regulatio n of PSII and the transition from state 1 to state 2. We propose that acetate-induced stimulation of the chlororespiratory electron flow triggers the regulation of PSII.
TL;DR: By using subtracted probes, two cDNA clones of rice, EL2 and EL3, were isolated as genes responsive within 6 min to N-acetylchitoheptaose, a potent biotic elicitor for phytoalexin biosynthesis.
Abstract: By using subtracted probes, two cDNA clones of rice, EL2 and EL3, were isolated as genes responsive within 6 min to jV-acetylchit oheptaose, a potent biotic elicitor for phytoalexin biosynthesis. Analyses of the sequence of the cDNAs showed that both of EL2 and EL3 encoded basic proteins with no significant similarities to those of known genes.
TL;DR: Results indicate that high photolyase activity is present in cucumber cotyledons and that repair activities in cucumbers are different from those reported in Arabidopsis, in which (6-4)photoproducts are photorepaired more rapidly than CPDs.
Abstract: Photoinduced lesions in DNA, namely, cyclobutane pyrimidine dimers (CPDs) and pyrimidine-(6-4)-pyrimidone photoproducts [(6-4)photoproducts], in cucumber cotyledons that had been irradiated with naturally occurring levels of UV-B (290-320 nm) were quantitated by enzyme-linked immunosorbent assays with monoclonal antibodies specific to each type of photolesion. Induction of these photolesions was dependent on temperature and their extent was reduced by simultaneous irradiation with white light. The dark repair of both types of photolesion was undetectable. Light-dependent removal of (6-4)photoproducts was very slow, with 50% removal in 4 h. By contrast, 50% of initial CPDs were removed within 15 min. Both photorepair processes were dependent on the intensity of white light and were sensitive to temperature. These results indicate that high photolyase activity is present in cucumber cotyledons and that repair activities in cucumber cotyledons are different from those reported in Arabidopsis, in which (6-4)photoproducts are photorepaired more rapidly than CPDs.
TL;DR: It is likely that ethylene biosynthesis in internodes of deep water rice is controlled, at least in part, at the level of ACC oxidase, which accumulates in the air spaces of submerged internodes.
Abstract: Partial submergence greatly stimulates internodal growth in deepwater rice (Oryza sativa L.). Previous work has shown that the effect of submergence is, at least in part, mediated by ethylene, which accumulates in the air spaces of submerged internodes. To investigate the expression of the genes encoding ethylene biosynthetic enzymes during accelerated growth of deepwater rice, we cloned a 1-aminocyclopropane-1-carboxylate (ACC) oxidase cDNA (OSACO1) from internodes of submerged plants and measured the activity of the enzyme in tissue extracts with an improved assay. We found an increase in ACC oxidase mRNA levels and enzyme activity after 4 to 24 h of submergence. Thus, it is likely that ethylene biosynthesis in internodes of deepwater rice is controlled, at least in part, at the level of ACC oxidase.
TL;DR: Monodehydroascorbate radical was determined in leaf segments of several plant species using electron paramagnetic resonance spectrometry, indicating the participation of the photoproduced superoxide and the hydrogen peroxide derived from the superoxide in the production of MDA in chloroplasts.
Abstract: Monodehydroascorbate radical (MDA) was determined in leaf segments of several plant species using electron paramagnetic resonance spectrometry. When the leaves were young and healthy, MDA was often below detection level in both the light and dark. However, in senescent leaves, higher levels of MDA were observed in the light than in the dark. After removal of ascorbate by infiltration of such leaves with ascorbate oxidase, dark-signals of MDA did not disappear; thus the apoplast was not a major source of MDA in the dark. Methylviologen induced high levels of light-depende nt MDA, indicating the participation of the photoproduced superoxide and the hydrogen peroxide derived from the superoxide in the production of MDA in chloroplasts. The photoproduction of MDA was greatly enhanced by intense light, water stress, and suppression of the photosynthetic reactions due to either infiltration or cyanide. Thus, MDA is a sensitive endogeneous probe of oxidative stress in leaf tissues in the sense that increased MDA levels indicate either increased oxidation of ascorbate or decreased efficiency of ascorbate regeneration, or a combination of both.
TL;DR: Apoplastic peroxidase isoenzymes from stems of Nicotiana tabacum rapidly oxidized sinapic acid and sinapyl alcohol, in addition to 4-coumaric acid, ferulic acid and coniferyl alcohol as mentioned in this paper.
Abstract: Apoplastic peroxidase isoenzymes from stems of Nicotiana tabacum rapidly oxidized sinapic acid and sinapyl alcohol, in addition to 4-coumaric acid, ferulic acid and coniferyl alcohol. By contrast, the peroxidase isoenzymes from stems of Vigna angularis oxidized sinapic acid and sinapyl alcohol quite slowly but rapidly oxidized compounds with a 4-hydroxyphenyl or a guaiacyl group. However, the oxidation of sinapyl alcohol was greatly enhanced by 4-coumaric acid, ferulic acid and an ester of ferulic acid. Intercellular washing fluid of V. angularis, which contained apoplastic components, also enhanced the oxidation of sinapyl alcohol. Based on these results, a possible mechanism for the oxidation of sinapyl alcohol is discussed on the assumption that the biosynthesis of lignin proceeds mainly via peroxidases which cannot oxidize sinapyl alcohol in V. angularis.