Regulation by ABA of osmotic-stress-induced changes in protein synthesis in tomato roots

Polypeptide synthesis and accumulation were examined in the roots of tomato seedlings exposed to a polyethylene glycol‐imposed water deficit stress. In these roots, the synthesis of a number of polypeptides was induced, while that of several others was enhanced or repressed. To examine the role played by abscisic acid (ABA) in co‐ordinating the accumulation of these proteins, water‐deficit‐stress‐responsive polypeptide synthesis was investigated in the roots of the ABA‐deficient mutant flacca. In the roots of this mutant, the ability to accumulate a complete set of water‐deficit‐stress‐responsive polypeptides was impaired, indicating that ABA is required for their synthesis. The role of ABA was further examined by exposing the roots of both genotypes to exogenous ABA, which, with one exception, elicited the accumulation of all water‐deficit‐stress‐responsive proteins. Polyethylene glycol‐induced polypeptide accumulation was accompanied by a 1·6‐fold increase in the level of endogenous ABA in the roots of wild‐type plants and a 5‐fold increase in the roots of flc. Thus, although the absolute level was lower than that of the wild‐type, flc has the capacity to accumulate ABA in its roots. When fluridone was used to prevent the biosynthesis of ABA, the accumulation of several water‐deficit‐stress‐responsive polypeptides was reduced further. The synthesis of polypeptides was also examined in the roots of salt‐treated seedlings. Salt altered the accumulation of several polypeptides, all of which were previously observed in water‐deficit‐stressed roots, indicating that their synthesis was the result of the osmotic component of the salt stress. However, the accumulation of these polypeptides was not impaired in flc roots, indicating that the role played by ABA in regulating their accumulation in salt‐and polyethylene glycol‐treated roots differs. As such, salt‐ and water‐deficit‐stress‐induced changes in gene expression may be effected by different mechanisms, at least at the level of polypeptide accumulation.     

Adaptation versus shock response to polyethylene glycol-induced low water potential in cultured potato cells

We compared long-term adaptation versus short-term or shock response of potato ( Solanum tuberosum ) cells to polyethylene glycol (PEG)-induced low water potential. Potato cells, which were allowed to adapt gradually to a decreasing water potential, were able to grow actively in a medium containing 20% PEG. In contrast, no appreciable gain in dry weight was observed in potato cells shocked by abrupt transfer to the same medium. PEG-adapted cells were also salt-tolerant, as they were able to proliferate in a medium supplemented with 200 m M NaCl. No visible ultrastructural changes of mitochondria or proplastids were observed in adapted cells at values of low water potential (about −2.0 MPa), which caused membrane disruption and appearance of lipid droplets in unadapted cells. ABA cellular content increased 5-fold in PEG-shocked cells but no significant increase was found in PEG-adapted cells. The intracellular content of free proline increased 12.5 times over the basal level in PEG-adapted cells and 6.5 times in PEG-shocked cells. As shown by in vivo protein labeling, shock conditions strongly inhibited protein synthesis, which was completely recovered in PEG-adapted cells. Osmotin, a protein associated with salt adaptation in tobacco, was constitutively expressed at a high level in PEG-adapted cells and accumulated in PEG-shocked cells only three days after the transfer in a medium supplemented with 20% PEG. Proline and osmotin accumulation were coincident with the increase in cellular ABA content in PEG-shocked cells, but not in PEG-adapted cells. These data suggest that this hormone is mainly involved in shock response rather than long-term adaptation.     

Dehydrin-like proteins in castor bean seeds and seedlings are differentially produced in response to ABA and water-deficit-related stresses

The stress inducibility of dehydrin protein production in seedlingsof castor bean was analysed by subjecting them to ABA and variouswater-deficit-related treatments including desiccation, waterstress, high salt, high osmolarity, and low temperature. A furthergoal was to determine whether the immature seed (at stages priorto major dehydrin synthesis) would respond in a similar mannerto these stresses. A number of dehydrin-like proteins increasedin seedlings subjected to the various stress treatments. Inthe endosperm, these appear to be different from the dehydrin-relatedpolypeptides that are induced during late seed development andwhich persist following germination/growth of mature seeds.In the endosperm of seedlings, ABA, water stress and desiccationinduced the same dehydrin polypeptides, while high osmolarity,high salt and low temperature induced a different set. Stress-specificdifferences in dehydrin synthesis were also found in the cotyledonsand radicle of castor bean seedlings; however, dehydrins indu-cibleby exogenous ABA were consistently produced. Immature seedstreated with ABA or subjected to stress responded by producingdehydrin-like proteins associated with late development; however,the same proteins were induced following detachment of immatureseeds from the parent plant and maintenance on water. When seedlingswere exposed simultaneously to GA and either ABA, high salt,or low temperature, dehydrin production was suppressed. It isconcluded that dehydrin production in castor bean is tissue-specificand is dependent upon the physiological stage of the seed. Inthe endosperm, the response to different stresses may rely uponmore than one signal trans-duction pathway. Key words: Dehydrin, castor bean, ABA, desiccation     

Effect of Abscisic Acid, Osmoticum, and Desiccation on Synthesis of Storage Proteins during the Development of White Spruce Somatic Embryos

The effect of abscisic acid (ABA), non-permeating osmoticumand desiccation treatment on storage protein synthesis duringmaturation of somatic embryos of Picea glauca (Moench) Voss.was examined. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis(SDS-PAGE) and Western blot analysis demonstrated that someof the major crystalloid and matrix polypeptides were absentfrom somatic embryos maturing on medium containing ABA and lowosmoticum. However, treatment with polyethylene glycol-4000(PEG) in combination with ABA resulted in the synthesis of aspectrum of storage polypeptides resembling that of mature zygoticembryos. These storage proteins accumulated throughout an 8-weekculture period, resulting in a threefold higher protein contentthan somatic embryos maturing for the same time in the absenceof PEG. The structure and distribution of protein bodies incells of these osmotically treated somatic embryos was similarto that in cells of mature zygotic embryos. Treatment with 5·0-7·5%PEG prevented catabolism of the accumulated storage polypeptidesduring desiccation. The optimal culture conditions for somaticembryo maturation and storage protein deposition was 16 µMABA and 7·5% PEG for 8 weeks followed by desiccation.Analysis of mRNAs by in vitro translation and immunoprecipitationof translated products showed that the crystalloid protein mRNAprofiles of zygotic and those of somatic embryos maturing on16 µM ABA in the absence of PEG were similar. The differencesobserved in the pattern of accumulated polypeptides in thesesomatic embryos and those of mature zygotic embryos, therefore,indicates that storage-protein synthesis in response to osmoticumis in part regulated at the translational level. During regenerationof somatic embryos to plantlets the storage polypeptides wererapidly utilized in a manner similar to that in zygotic seedlings.Copyright1993, 1999 Academic Press Desiccation, osmotic stress, storage proteins, Picea, embryogenesis—somatic, mRNA (crystalloid protein)     

Drought- and ABA-Induced Changes in Polypeptide and mRNA Accumulation in Tomato Leaves

Drought stress triggers abscisic acid (ABA) biosynthesis resulting in ABA accumulation. The ABA-deficient tomato mutant, flacca (Lycopersicon esculentum Mill. cv Ailsa Craig), does not synthesize ABA in response to drought stress. This mutant has been used to distinguish polypeptides and in vitro translation products that are synthesized during drought stress in response to elevated ABA levels from those that are induced directly by altered water relations. A set of polypeptides and in vitro translation products was synthesized during drought stress in the wild type. These polypeptides and in vitro translation products were synthesized to a lesser extent in the drought-stressed ABA-deficient mutant. Treatment of flacca with ABA resulted in the synthesis of the drought-stress-induced polypeptides and in vitro translation products. These results support the hypothesis that many of the polypeptides that are synthesized during drought are regulated by alterations in ABA concentration. Similarly, the mRNA population was altered by ABA during drought stress.     

Salt-induced protein synthesis in tomato roots: the role of ABA

The role played by abscisic acid (ABA) in regulating salt-induced protein synthesis was investigated in roots of tomato (Lycopersicon esculentum Mill. cv. Ailsa Craig). Roots of 9-d-old Ailsa Craig (AC) seedlings and the near-isogenic ABA-deficient mutant, flacca (flc), were exposed to salt which elicited the appearance of novel polypeptides and both repressed and enhanced the synthesis of others. The polypeptide profiles of salt-treated AC and flc roots were similar suggesting that the synthesis of most novel polypeptides in salt-treated roots is not dependent on an elevated level of endogenous ABA. Exogenous ABA and a combined ABA/salt treatment were applied to the roots of AC and flc. Exogenous ABA, in the absence of salt, induced the accumulation of several polypeptides that were unique to this treatment as well as a subset of those synthesized in salt-treated roots. Interestingly, in roots exposed to the combined ABA/salt treatment, only those polypeptides that accumulated in both ABA or salt-treated roots were synthesized. Endogenous ABA levels increased 2-fold in salt-treated AC roots and 14-fold in salt-treated flc roots. Although the absolute level of ABA was lower in salt-treated flc than in AC, this demonstrates that flc has the capacity to accumulate some ABA in its roots following a salt treatment. Since it is possible that this level of ABA was sufficient to induce the changes in polypeptide synthesis observed in salt-treated roots of flc, the salt-induced accumulation of endogenous ABA was prevented by treating AC roots with fluridone. In these roots, the set of salt-induced polypeptides was similar to that observed in salt-treated roots indicating that an elevated level of endogenous ABA may not play a major role in regulating the accumulation of most salt-induced proteins in tomato roots.Keywords: Salt stress, ABA, polypeptide synthesis, roots.      

Effects of water stress on plant growth and root proteins in three cultivars of rice (Oryza sativa) with different levels of drought tolerance

Rice ( Oryza sativa L.) is considered a drought-sensitive crop species; however, within this species, there are considerable varietal differences in sensitivity to this environmental stress. In the present work, the effect of water stress on germination, plant growth and root proteins in three rice cultivars (Sinaloa, IR10120 and Chiapas) was analyzed. Seed germination and plant growth were found to be significantly inhibited by polyethylene glycol (PEG)-imposed water deficit in cv. Sinaloa; cvs IR10120 and Chiapas were more tolerant to water stress. Fluorographs of two-dimensional electropherograms of in vivo-labeled polypeptides were analyzed to identify changes in the root protein patterns that resulted when plants were grown in the presence of 10% PEG for 10 days. The treatment induced or increased the synthesis of eight polypeptides or groups of polypeptides in cv. Sinaloa, seven in cv, IR10120 and four in cv. Chiapas. The synthesis of several polypeptides was decreased by the PEG treatment in cv. Sinaloa and cv. IR10120. Most of these PEG-induced changes in the root protein patterns were cultivar-specific and only one 26-kDa protein with a pI of 6.0 was induced by water deficit in the two cultivars Sinaloa and IR10120.     

Globulin-1 gene expression in regenerable<Emphasis Type="Italic"> Zea mays</Emphasis> (maize) callus

Since maize callus cultures regenerate plants via somatic embryogenesis, one might expect to find similar proteins in both zygotic embryos and tissue cultures. The 63-kD globulin protein designated GLB1, the expression of which is regulated by abscisic acid (ABA), is one such protein. When maize Type I regenerable callus was exposed for 24 h to 0.1 m M ABA or a water stress induced by 0.53 M mannitol, GLB1 was produced as determined by Western analysis. This protein was not detected in ABA or mannitol-treated regenerable cultured tissue of a null genotype or in tissues not exposed to ABA or water stress. Exposure to ABA in the culture medium increased the callus ABA levels greatly but a mannitol-induced water stress had only a small effect on ABA levels. Regenerable callus exposed to 0.1 m M ABA also produced mRNA that hybridized on a Northern blot with a globulin- 1 gene ( Glb1) probe. When both Type I and Type II regenerable cultured tissues were exposed to regeneration medium without ABA or mannitol, several GLB1 antibody immunoreactive proteins were produced. These proteins were not detected in regenerated plants nor in non-regenerable callus treated with ABA. These results suggest that: (1) at least for expression of Glb1, somatic embryogenesis is similar to zygotic embryogenesis, (2) there may be a regulatory role for auxin in the processing of Glb1-encoded polypeptides since fewer are seen when dicamba is present in the medium, (3) ABA has a role in somatic embryogenesis, and (4) regenerability of a maize callus culture may be assessed by treating the cultured tissue with 0.1 m M ABA to determine if GLB1 proteins are induced.     

盐胁迫下苜蓿中盐蛋白的诱导产生

盐胁迫下苜蓿叶片中蛋白质的合成受到抑制,而其离体叶绿体中蛋白质合成增强,ABA阻碍了后者的蛋白质合成。NaCl胁迫下,“松江”和“肇东”两品种的根和叶中均无新多肽出现。在盐敏感的“松江”品种离体叶绿体中,NaGl诱导70,65,60和43kD4种多肽产生,ABA诱导60和17kD两种多肽产生;在较抗盐的“肇东”品种离体叶绿体中,NaGl诱导83,80kD和43kD3种多肽产生,但100mmol/L NaCl并不诱导83kD多肽出现,ABA无明显作用。两品种的43kD多肽和肇东品种的80kD多肽都存在于类囊体膜上,而松江品种的60kD多肽则存在于叶绿体间质中。     

三氟啦嗪（TFP）、ABA处理对小麦幼苗及悬浮培养细胞中诱导蛋白的影响

水分胁迫及ABA处理能诱导丰抗8号小麦幼苗及其悬浮培养细胞中44.2kD蛋白亚基的产生或大量合成。不同浓度的CaM抑制剂三氟啦嗪（Trifluoperazine)处理,对丰抗8号小麦幼苗在水分胁迫时产生的44.2kD蛋白亚基没有明显抑制作用,对悬浮培养细胞中由ABA＋PEG所诱导的该蛋白含量的升高影响较小,但能抑制细胞中由ABA诱导的44.2kD蛋白亚基百分含量的增加。表明由单纯激素（ABA）引起的信号传递途径可能与CaM有关,且较为简单,而水分胁迫或水分胁迫＋ABA引起的信号传递途径可能比单纯激素引起的胞人信号传递过程更复杂。     

Role of abscissic acid in water stress-induced antioxidant defense in leaves of maize seedlings

Roles of abscisic acid (ABA) in water stress-induced oxidative stress were investigated in leaves of maize ( Zea mays L.) seedlings exposed to water stress induced by polyethylene glycol (PEG 6000). Treatment with PEG at -0.7 MPa for 12 and 24 h led to a reduction in leaf relative water content (RWC) by 7.8 and 14.1%, respectively. Duration of the osmotic treatments is considered as mild and moderate water stress. The mild water stress caused significant increases in the generation of superoxide radical ( O 2 - ) and hydrogen peroxide (H 2 O 2 ), the activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) and the contents of ascorbate (ASC), reduced glutathione (GSH). The moderate water stress failed to further enhance the capacity of antioxidant defense systems, as compared to the mild water stress. The contents of catalytic Fe, which is critical for H 2 O 2 -dependent hydroxyl radical ( •OH) production, and the oxidized forms of ascorbate and glutathione pools, dehydroascorbate (DHA) and oxidized glutathione (GSSG), markedly increased, a significant oxidative damage to lipids and proteins took place under the moderate water stress. Pretreatment with ABA caused an obvious reduction in the content of catalytic Fe and significant increases in the activities of antioxidant enzymes and the contents of non-enzymatic antioxidants, and then significantly reduced the contents of DHA and GSSG and the degrees of oxidative damage in leaves exposed to the moderate water stress. Pretreatment with an ABA biosynthesis inhibitor, tungstate, significantly suppressed the accumulation of ABA induced by water stress, reduced the enhancement in the capacity of antioxidant defense systems, and resulted in an increase in catalytic Fe, DHA and GSSG, and oxidative damage in the water-stressed leaves. These effects were completely prevented by addition of ABA, which raised the internal ABA content. Our data indicate that ABA plays an important role in water stress-induced antioxidant defense against oxidative stress.     

Mass spectrometry proteomic analysis of stress adaptation reveals both common and distinct response pathways in<Emphasis Type="Italic"> Propionibacterium freudenreichii</Emphasis>

Microorganisms used in food technology and probiotics are exposed to technological and digestive stresses, respectively. Traditionally used as Swiss-type cheese starters, propionibacteria also constitute promising human probiotics. Stress tolerance and cross-protection in Propionibacterium freudenreichii were thus examined after exposure to heat, acid, or bile salts stresses. Adapted cells demonstrated acquired homologous tolerance. Cross-protection between bile salts and heat adaptation was demonstrated. By contrast, bile salts pretreatment sensitized cells to acid challenge and vice versa. Surprisingly, heat and acid responses did not present significant cross-protection in P. freudenreichii. During adaptations, important changes in cellular protein synthesis were observed using two-dimensional electrophoresis. While global protein synthesis decreased, several proteins were overexpressed during stress adaptations. Thirty-four proteins were induced by acid pretreatment, 34 by bile salts pretreatment, and 26 by heat pretreatment. Six proteins are common to all stresses and represent general stress-response components. Among these polypeptides, general stress chaperones, and proteins involved in energetic metabolism, oxidative stress response, or SOS response were identified. These results bring new insight into the tolerance of P. freudenreichii to heat, acid, and bile salts, and should be taken into consideration in the development of probiotic preparations.     

Role of Abscisic Acid in Water Stress-induced Antioxidant Defense in Leaves of Maize Seedlings

Roles of abscisic acid (ABA) in water stress-induced oxidative stress were investigated in leaves of maize ( Zea mays L.) seedlings exposed to water stress induced by polyethylene glycol (PEG 6000). Treatment with PEG at &#109 0.7 MPa for 12 and 24 h led to a reduction in leaf relative water content (RWC) by 7.8 and 14.1%, respectively. Duration of the osmotic treatments is considered as mild and moderate water stress. The mild water stress caused significant increases in the generation of superoxide radical ( O 2 &#109 ) and hydrogen peroxide (H 2 O 2 ), the activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) and the contents of ascorbate (ASC), reduced glutathione (GSH). The moderate water stress failed to further enhance the capacity of antioxidant defense systems, as compared to the mild water stress. The contents of catalytic Fe, which is critical for H 2 O 2 -dependent hydroxyl radical ( &#148 OH) production, and the oxidized forms of ascorbate and glutathione pools, dehydroascorbate (DHA) and oxidized glutathione (GSSG), markedly increased, a significant oxidative damage to lipids and proteins took place under the moderate water stress. Pretreatment with ABA caused an obvious reduction in the content of catalytic Fe and significant increases in the activities of antioxidant enzymes and the contents of non-enzymatic antioxidants, and then significantly reduced the contents of DHA and GSSG and the degrees of oxidative damage in leaves exposed to the moderate water stress. Pretreatment with an ABA biosynthesis inhibitor, tungstate, significantly suppressed the accumulation of ABA induced by water stress, reduced the enhancement in the capacity of antioxidant defense systems, and resulted in an increase in catalytic Fe, DHA and GSSG, and oxidative damage in the water-stressed leaves. These effects were completely prevented by addition of ABA, which raised the internal ABA content. Our data indicate that ABA plays an important role in water stress-induced antioxidant defense against oxidative stress.     

Dithiothreitol and PEG Induced Combined Stress May Affect the Expressions of ABA Aldehyde Oxidase,Sucrose Synthase and Proline Metabolic Genes in Maize Seedlings

The endoplasmic reticulum (ER) is an organelle in the cell where proteins are created and folded. Folding is a very elaborate process that is often interrupted by various biotic and abiotic stresses, leading to the formation of unfolded and misfolded proteins called ER stress. Dithiothreitol (DTT)-induced unfolded protein response (UPR) in endoplasmic reticulum (ER) has been recently reported in plants. Also, previous studies demonstrated that treatment with polyethylene glycol (PEG₆₀₀₀) could stimulate water deficit in crops. However, further researches should be conducted to elucidate the molecular mechanism of ER stress response and the relationship between water deficiency and ER. In this study, we examined the expressions of sucrose synthase (SuS) gene, proline metabolic genes and abscisic aldehyde oxidase (AAO3) gene in maize seedlings that were subjected to DTT and PEG induced combined stresses by using quantitative real-time RT-PCR. Three weeks old detached maize seedlings were treated with or without DTT and PEG₆₀₀₀ for 12 h. The treatment with DTT increased about 2-fold the expression of gene encoding proline synthesis enzyme, pyrroline-5-carboxylate synthetase (P5CS) but no statistically affected the proline catabolism enzyme, proline dehydrogenase (ProDH) in comparison with un-treated seedlings. PEG treatment was also up-regulated P5CS while it was down-regulated ProDH. The relative expression levels of SuS and AAO3 genes statistically enhanced about 2.5 fold under the DTT-induced ER stress. Likewise, the expression levels of SuS and AAO3 genes were up-regulated in the detached seedlings exposed to PEG-induced water deficit. Conversely, the induced gene expressions were down-regulated under the combined stress, the DTT-induced ER stress and PEG-induced water deficit in comparison with the singular stress responses (DTT or PEG). The results indicated that the expressions of genes, related to the synthesis of some signal osmolyte compounds such as proline and sucrose can be suppressed when ER stress occurred under water deficiency in maize seedlings. The changes in the expressions of genes involved in osmolyte and ABA metabolism can be related to ER stress response as well as variations in water status.     

Relations between MAPK phosphorylation and ABA level in <Emphasis Type="Italic">Malus sieversii</Emphasis> under water stress

A correlation between protein kinase phosphorylation and ABA level was studied in Malus sieversii (Ledeb.) Roem. seedlings under water stress. The seedlings were treated with PEG 6000 for imitation of water stress, and the MAPK activity and ABA content in each treatment were then determined. We demonstrated that the increase in the activities of the total protein kinase (TPK) and mitogen-activated protein kinase (MAPK) after treatment with 20% PEG 6000 appeared to result in a high level of ABA. MAPK activity accounted for 76.8% of TPK activity. The activity peaks of TPK and MAPK preceded the highest level of ABA accumulation. It is interesting that the ABA level in roots and leaves of seedlings pretreated with 2 × 10⁻² mM exogenous ABA for 20 min following treatment by 20% PEG 6000 was much higher than that of seedlings treated with exogenous ABA only. We analyzed the influence of MAPK inhibitor ITU (5-iodotubercidin) on ABA accumulation in the seedlings of M. sieversii under water stress and showed that 1 μM ITU significantly decreased the ABA level induced by a water loss. However, the phosphoesterase inhibitor PAO (phenylarisine oxide) enhanced ABA accumulation, indicating that the phosphorylated MAPK was correlated to ABA synthesis. Together, these results suggest that MAPK phosphorylation played an important role in ABA accumulation under water stress, and MAPK might mediate the signal transduction of ABA synthesis.     

Expression and molecular cloning of drought-induced genes in the wild tomato Lycopersicon chilense.

Protein synthesis and translatable mRNA population changes induced during water stress were studied in leaves of a drought-resistant wild relative of tomato, Lycopersicon chilense, using one- and two-dimensional polyacrylamide gel electrophoresis. Under our experimental conditions, water deficit did not significantly affect total protein synthesis capacity. However, it induced biphasic synthesis of a new set of proteins. These newly synthesized proteins resumed to control levels upon rehydration of the plants. Certain drought-induced proteins also accumulated in leaves subjected to heat shock (39 degrees C) or exogenous abscisic acid (ABA, 1 mM) treatments. A cDNA library was constructed using poly(A)+ RNA from leaves of plants exposed to drought stress for 4 days. Differential screening of the library identified three groups of clones corresponding to drought- and ABA-induced mRNAs. Northern blot analysis showed that the genes of selected clones respond differently to the different environmental stresses. Our data clearly demonstrate that water stress alters gene expression in L. chilense plants resulting in the synthesis of new proteins, of which several respond to high temperature stress and others to an osmotic effect. These responses are in part modulated by ABA.     

Genetic Variability in Recovery Growth and Synthesis of Stress Proteins in Response to Polyethylene Glycol and Salt Stress in Finger Millet

Marked differences were found among 28 finger millet genotypes(Eleusine coracana Gaertn.) in acquired tolerance to osmoticstress as assessed by the recovery of root growth from severestress [-1·2 MPa polyethylene glycol, (PEG) or 400 mMNaCl]. However, these differences in tolerance were observedonly when the seedlings were subjected to a preceding mild inductionstress (-0·6 MPa PEG or 200 mM NaCl). In two contrastinggenotypes, synthesis of stress-induced proteins was studied.Proteins with apparent molecular weight of 70-72, 52, 37, 34and 23 kDa were synthesized in the highly responsive genotype(GE 415) and poorly responsive (VL 481) genotype following amild induction stress (200 mM NaCl). However, GE-415 synthesizeda 54 kDa protein that was not observed in VL-481. Addition ofabscisic acid (ABA) to the induction medium containing 200 mMNaCl enhanced the acquired tolerance of finger millet seedlingsover those without ABA in association with the appearance ofseveral ABA-responsive proteins. GE-415 required much less ABAthan VL-481 to obtain the same response. With 10 µM ABA+ 200 mM, A NaCl induction stress, GE-415 had significantlyhigher endogenous ABA. In association with higher levels ofABA, GE-415 had greater recovery root growth following severestress from 600 mM NaCl. Pretreatment with 10 µM ABA +200 mM NaCl induced several proteins with apparent molecularweights of 70-72, 54, 45, 36, 29 and 21 kDa in both genotypes.Qualitatively, GE-415 synthesized a unique 23-24 kDa proteinand quantitatively there was significantly more of the 21 kDaprotein in GE-415 compared to VL-481. The results indicate thatthe synthesis of stress proteins is correlated with the observedvariation in acquired tolerance of the two genotypes.Copyright1995, 1999 Academic Press Eleusine coracana Gaertn., salinity, polyethylene glycol, stress proteins, ABA, ABA-responsive proteins, finger millet seedlings     

Accumulation of Group 3 Late Embryogenesis Abundant Proteins in Zea mays Embryos : Roles of Abscisic Acid and the Viviparous-1 Gene Product

Several different types of proteins that are modulated by abscisic acid (ABA) accumulate in developing embryos of maize (Zea mays L.). Some of these proteins are specific to the developing seed, such as the storage globulin, GLB1, whereas others are involved in general responses to water deficit. Here we describe a maize protein family of this second type, a Group 3 late embryogenesis abundant (MLG3). Like other proteins of this class, MLG3 polypeptides are ABA-responsive. They are found in maturing seeds and in dehydrating plant tissues. Antigenically related proteins are found in other cereals. To distinguish the regulation of developmentally programmed ABA responses from those that are environmentally induced, we compared the ontological pattern and accumulation requirements of MLG3 polypeptides with those we previously described for GLB1. GLB1 accumulation begins early in the maturation phase and specifically requires high levels of ABA and the participation of the Viviparous-1 (Vp1) gene product. Vp1 is required for other ABA-modulated events in maize seed development as well. In experiments using vp1 mutants and mutants deficient in ABA synthesis (vp5 mutation), we show that MLG3 accumulation also is dependent upon ABA, but it shows striking differences from GLB1. MLG3 accumulates much later in embryogenesis, coincident with the onset of dehydration. In contrast to GLB1, MLG3 proteins can be induced by de novo ABA synthesis in response to culturing in high osmoticum. Unlike GLB1, MLG3 has no specific requirement for the Vp1 gene product.