Cytosolic glyceraldehyde-3-phosphate dehydrogenases interact with phospholipase Dδ to transduce hydrogen peroxide signals in the Arabidopsis response to stress

Reactive oxygen species (ROS) are produced in plants under various stress conditions and serve as important mediators in plant responses to stresses. Here, we show that the cytosolic glycolytic enzymes glyceraldehyde-3-phosphate dehydrogenases (GAPCs) interact with the plasma membrane-associated phospholipase D (PLDδ) to transduce the ROS hydrogen peroxide (H(2)O(2)) signal in Arabidopsis thaliana. Genetic ablation of PLDδ impeded stomatal response to abscisic acid (ABA) and H(2)O(2), placing PLDδ downstream of H(2)O(2) in mediating ABA-induced stomatal closure. To determine the molecular link between H(2)O(2) and PLDδ, GAPC1 and GAPC2 were identified to bind to PLDδ, and the interaction was demonstrated by coprecipitation using proteins expressed in Escherichia coli and yeast, surface plasmon resonance, and bimolecular fluorescence complementation. H(2)O(2) promoted the GAPC-PLDδ interaction and PLDδ activity. Knockout of GAPCs decreased ABA- and H(2)O(2)-induced activation of PLD and stomatal sensitivity to ABA. The loss of GAPCs or PLDδ rendered plants less responsive to water deficits than the wild type. The results indicate that the H(2)O(2)-promoted interaction of GAPC and PLDδ may provide a direct connection between membrane lipid-based signaling, energy metabolism and growth control in the plant response to ROS and water stress.     

WD40‐REPEAT 5a functions in drought stress tolerance by regulating nitric oxide accumulation in Arabidopsis

Nitric oxide (NO) generation by NO synthase (NOS) in guard cells plays a vital role in stomatal closure for adaptive plant response to drought stress. However, the mechanism underlying the regulation of NOS activity in plants is unclear. Here, by screening yeast deletion mutants with decreased NO accumulation and NOS‐like activity when subjected to H₂O₂ stress, we identified TUP1 as a novel regulator of NOS‐like activity in yeast. Arabidopsis WD40‐REPEAT 5a (WDR5a), a homolog of yeast TUP1, complemented H₂O₂‐induced NO accumulation of a yeast mutant Δtup1, suggesting the conserved role of WDR5a in regulating NO accumulation and NOS‐like activity. This note was further confirmed by using an Arabidopsis RNAi line wdr5a‐1 and two T‐DNA insertion mutants of WDR5a with reduced WDR5a expression, in which both H₂O₂‐induced NO accumulation and stomatal closure were repressed. This was because H₂O₂‐induced NOS‐like activity was inhibited in the mutants compared with that of the wild type. Furthermore, these wdr5a mutants were more sensitive to drought stress as they had reduced stomatal closure and decreased expression of drought‐related genes. Together, our results revealed that WDR5a functions as a novel factor to modulate NOS‐like activity for changes of NO accumulation and stomatal closure in drought stress tolerance.     

OsASR5 enhances drought tolerance through a stomatal closure pathway associated with ABA and H2O2 signalling in rice

Drought is one of the major abiotic stresses that directly implicate plant growth and crop productivity. Although many genes in response to drought stress have been identified, genetic improvement to drought resistance especially in food crops is showing relatively slow progress worldwide. Here, we reported the isolation of abscisic acid, stress and ripening (ASR) genes from upland rice variety, IRAT109 (Oryza sativa L. ssp. japonica), and demonstrated that overexpression of OsASR5 enhanced osmotic tolerance in Escherichia coli and drought tolerance in Arabidopsis and rice by regulating leaf water status under drought stress conditions. Moreover, overexpression of OsASR5 in rice increased endogenous ABA level and showed hypersensitive to exogenous ABA treatment at both germination and postgermination stages. The production of H₂O₂, a second messenger for the induction of stomatal closure in response to ABA, was activated in overexpression plants under drought stress conditions, consequently, increased stomatal closure and decreased stomatal conductance. In contrast, the loss‐of‐function mutant, osasr5, showed sensitivity to drought stress with lower relative water content under drought stress conditions. Further studies demonstrated that OsASR5 functioned as chaperone‐like protein and interacted with stress‐related HSP40 and 2OG‐Fe (II) oxygenase domain containing proteins in yeast and plants. Taken together, we suggest that OsASR5 plays multiple roles in response to drought stress by regulating ABA biosynthesis, promoting stomatal closure, as well as acting as chaperone‐like protein that possibly prevents drought stress‐related proteins from inactivation.     

TaTIP41 and TaTAP46 positively regulate drought tolerance in wheat by inhibiting PP2A activity

Drought is a major environmental stress limiting global wheat(Triticum aestivum) production. Exploring drought tolerance genes is important for improving drought adaptation in this crop. Here, we cloned and characterized TaTIP41, a novel drought tolerance gene in wheat. TaTIP41 is a putative conserved component of target of rapamycin(TOR)signaling, and the Ta TIP41 homoeologs were expressed in response to drought stress and abscisic acid(ABA). The overexpression of Ta TIP41 enhanced drought tole...     

Phospholipase Dδ is involved in nitric oxide-induced stomatal closure

Nitric oxide (NO) has recently emerged as a second messenger involved in the complex network of signaling events that regulate stomatal closure. Little is known about the signaling events occurring downstream of NO. Previously, we demonstrated the involvement of phospholipase D (PLD) in NO signaling during stomatal closure. PLDδ, one of the 12 Arabidopsis PLDs, is involved in dehydration stress responses. To investigate the role of PLDδ in NO signaling in guard cells, we analyzed guard cells responses using Arabidopsis wild type and two independent pldδ single mutants. In this work, we show that pldδ mutants failed to close the stomata in response to NO. Treatments with phosphatidic acid, the product of PLD activity, induced stomatal closure in pldδ mutants. Abscisic acid (ABA) signaling in guard cells involved H₂O₂ and NO production, both required for ABA-induced stomatal closure. pldδ guard cells produced similar NO and H₂O₂ levels as the wild type in response to ABA. However, ABA- or H₂O₂-induced stomatal closure was impaired in pldδ plants. These data indicate that PLDδ is downstream of NO and H₂O₂ in ABA-induced stomatal closure.     

Increased expression of phospholipase Dα1 in guard cells decreases water loss with improved seed production under drought in Brassica napus

The activation of phospholipase Dα1 (PLDα1) produces lipid messenger phosphatidic acid and promotes stomatal closure in Arabidopsis. To explore the use of the PLDα1‐mediated signalling towards decreasing water loss in crop plants, we introduced Arabidopsis PLDα1 under the control of a guard cell–specific promoter AtKatI_pro into two canola (Brassica napus) cultivars. Multiple AtKatI_pro::PLDα1 lines in each cultivar displayed decreased water loss and improved biomass accumulation under hyperosmotic stress conditions, including drought and high salinity. Moreover, AtKatI_pro::PLDα1 plants produced more seeds than did WT plants in fields under drought. The results indicate that the guard cell–specific expression of PLDα1 has the potential to improve crop yield by enhancing drought tolerance.     

Identification of the Arabidopsis dry2/sqe1‐5 mutant reveals a central role for sterols in drought tolerance and regulation of reactive oxygen species

Squalene epoxidase enzymes catalyse the conversion of squalene into 2,3‐oxidosqualene, the precursor of cyclic triterpenoids. Here we report that the Arabidopsis drought hypersensitive/squalene epoxidase 1‐5 (dry2/sqe1‐5) mutant, identified by its extreme hypersensitivity to drought stress, has altered stomatal responses and root defects because of a point mutation in the SQUALENE EPOXIDASE 1 (SQE1) gene. GC‐MS analysis indicated that the dry2/sqe1‐5 mutant has altered sterol composition in roots but wild‐type sterol composition in shoots, indicating an essential role for SQE1 in root sterol biosynthesis. Importantly, the stomatal and root defects of the dry2/sqe1‐5 mutant are associated with altered production of reactive oxygen species. As RHD2 NADPH oxidase is de‐localized in dry2/sqe1‐5 root hairs, we propose that sterols play an essential role in the localization of NADPH oxidases required for regulation of reactive oxygen species, stomatal responses and drought tolerance.     

干旱胁迫对降香黄檀幼苗光合生理特性的影响

采用温室盆栽方法,设置对照(CK)、轻度(LS)、中度(MS)和重度(HS)干旱胁迫4个水分条件,研究不同水分条件对降香黄檀幼苗光合和生理特性的影响。结果表明:(1)随着干旱胁迫程度增加,降香黄檀幼苗叶片叶绿素总含量总体呈现出下降趋势。(2)降香黄檀幼苗叶片净光合速率、气孔导度、胞间CO2浓度和蒸腾速率随着干旱胁迫强度增加均呈现出先增加后降低趋势,且MS和HS处理下的气孔导度和胞间CO2浓度同时降低,此时幼苗光合能力的下降主要受气孔因素限制。(3)随着干旱胁迫强度的增加,降香黄檀幼苗叶片细胞膜相对透性、丙二醛含量、游离脯氨酸含量和POD活性均呈现出增加趋势,而同期SOD和CAT活性呈现出先升高后降低趋势。可见,降香黄檀幼苗在轻度干旱胁迫下可通过增加叶片保护酶活性来清除活性氧对其组织造成的伤害,但胁迫超过一定程度后保护酶活性下降,表明降香黄檀幼苗的耐旱能力有限。     

G protein and PLDδ are involved in JA to regulate osmotic stress responses in Arabidopsis thaliana

Jasmonic acid (JA) is regarded as an endogenous regulator which plays an important role in regulating plant growth, development and stress response. Using the seedlings of A. thaliana ecotype Col-0 (wild-type, WT), phospholipase Dδ (PLDδ) deficient mutant (pldδ), the G protein α subunit (GPA1) deficient mutant (gpa1-4), 9-Lipoxygenase (9-LOX) deficient mutants (lox1 and lox5) as materials, the effects of JA responding to osmotic stress and the functions of G protein and PLDδ in this response were investigated. The results showed that GPA1 involved in the regulation of JA to PLDδ under osmotic stress. Both GPA1 and PLDδ participated in the regulation of JA on the seed germination and osmotic tolerance. Exogenous MeJA reduced the EL and MDA in WT, but increased the EL and MDA in gpa1-4 and pldδ, indicating that GPA1 and PLDδ were involved in the protection of JA on the membrane. The genes expression levels, and the activities of PLDδ and LOX1 were significantly induced by osmotic stress. The LOX activity and JA content in pldδ seedings were lower obviously than those in WT, but were markedly increased and were higher than WT after applying phosphatidic acid (PA). These results demonstrated that JA responded to osmotic stress by regulating G protein and PLDδ in A. thaliana. PLDδ was located upstream of 9-LOX and involved in the JA biosynthesis.     

小麦叶片光合作用与其渗透调节能力的关系

在缓慢干旱条件下,小麦叶片渗透调节能力在一定范围内随胁迫程度的加剧而增加,而在快速干旱下,渗透调节能力丧失。小麦叶片通过渗透调节使光合速率和气孔导度对水分胁迫的敏感性降低,叶片维持较高的电子传递能力、RuBP羧化酶活性和叶绿体光合能量转换系统活性,并推迟了小麦叶片光合速率受气孔因素限制向叶肉细胞光合活性限制转变的时间。     

二氧化硫增强拟南芥植株对干旱的适应性

以模式植物拟南芥为材料,研究SO_2对植物干旱适应性的影响。采用分光光度法检测植物干旱生理指标的变化,并用半定量RT-PCR技术分析了拟南芥热激基因和干旱响应基因的转录水平。研究发现:4周龄拟南芥植株暴露于30mg/m3的SO_2后,6—72h间叶面气孔开度显著低于对照并逐渐减小,在暴露48h和72h时,热激转录因子HsfA2和热激基因Hsp17.7、Hsp17.6B、Hsp17.6C转录上调,干旱响应基因DREB2A、DREB2B和RD29A表达增强;在SO_2熏气72h后进行干旱胁迫,干旱期间SO_2预暴露植株的叶片相对含水量高于非熏气干旱处理组,植株萎蔫程度比后者明显减轻,且SO_2预暴露植株的地上组织中可溶性糖和脯氨酸含量升高,超氧化物歧化酶活性提高,丙二醛含量降低。结果表明:SO_2能降低气孔开度、提高抗氧化能力、上调热激基因和干旱响应基因转录,并能促进干旱期间植物细胞内渗透调节物质的合成和积累,促使抗氧化酶活性提高,从而降低干旱胁迫对植株造成的氧化损伤,增强拟南芥对干旱的适应性。植物通过基因转录应答、酶活性改变、渗透调节物质积累等,在适应环境高浓度SO_2的同时,提高了对干旱的适应性。