ZmWRKY104 positively regulates salt tolerance by modulating ZmSOD4 expression in maize

Salinity impairs plant growth, limiting agricultural development. It is desirable to identify genes responding to salt stress and their mechanism of action. We identified a function of the Zea mays WRKY transcription factor, Zm WRKY104, in salt stress response. Zm WRKY104 was localized in the nucleus and showed transcriptional activation activity. Phenotypic and physiological analysis showed that overexpression of Zm WRKY104 in maize increased the tolerance of maize to salt stress and alleviated salt-induced increases in O;accumulation, malondialdehyde(MDA) content, and percent of electrolyte leakage. Further investigation showed that Zm WRKY104 increased SOD activity by regulating Zm SOD4 expression. Yeast onehybrid, electrophoretic mobility shift test, and chromatin immunoprecipitation–quantitative PCR assay showed that Zm WRKY104 bound directly to the promoter of Zm SOD4 by recognizing the W-box motif in vivo and in vitro. Phenotypic, physiological, and biochemical analysis showed that Zm SOD4 increased salt tolerance by alleviating salt-induced increases in O;accumulation, MDA content, and percent of electrolyte leakage under salt stress. Taken together, our results indicate that Zm WRKY104 positively regulates Zm SOD4 expression to modulate salt-induced O;accumulation, MDA content, and percent of electrolyte leakage, thus affecting salt stress response in maize.

Calcineurin B-like protein 5(SiCBL5)in Setaria italica enhances salt tolerance by regulating Na^(+)homeostasis

Salinity,a major abiotic stress,reduces plant growth and severely limits agricultural productivity.Plants regulate salt uptake via calcineurin B-like proteins(CBLs).Although extensive studies of the functions of CBLs in response to salt stress have been conducted in Arabidopsis,their functions in Setaria italica are still poorly understood.The foxtail millet genome encodes seven CBLs,of which only SiCBL4 was shown to be involved in salt response.Overexpression of SiCBL5 in Arabidopsis thaliana sos3-1 mutant rescued its salt hypersensitivity phenotype,but that of other SiCBLs(SiCBL1,SiCBL2,SiCBL3,SiCBL6,and SiCBL7)did not rescue the salt hypersensitivity of the Atsos3-1 mutant.SiCBL5 harbors an N-myristoylation motif and is located in the plasma membrane.Overexpression of SiCBL5 in foxtail millet increased its salt tolerance,but its knockdown increased salt hypersensitivity.Yeast two-hybrid and firefly luciferase complementation imaging assays showed that SiCBL5 physically interacted with SiCIPK24 in vitro and in vivo.Cooverexpression of SiCBL5,SiCIPK24,and SiSOS1 in yeast conferred a high-salt-tolerance phenotype.Compared to wild-type plants under salt stress conditions,SiCBL5 overexpressors showed lower accumulations of Na^(+) and stronger Na^(+) efflux,whereas RNAi-SiCBL5 plants showed higher accumulations of Na^(+) and weaker Na^(+) efflux.These results indicate that SiCBL5 confers salt tolerance in foxtail millet by modulating Na^(+) homeostasis.

The C_2H_2 -type Zinc Finger Protein ZFP182 is Involved in Abscisic Acid-Induced Antioxidant Defense in Rice

C2H2 -type zinc finger proteins (ZFPs) are thought to play important roles in modulating the responses of plants to drought, salinity and oxidative stress. However, direct evidence is lacking for the involvement of these ZFPs in abscisic acid (ABA)-induced antioxidant defense in plants. In this study, the role of the rice (Oryza sativa L. sub. japonica cv. Nipponbare) C 2 H 2 -type ZFP ZFP182 in ABA-induced antioxidant defense and the relationship between ZFP182 and two rice MAPKs, OsMPK1 and OsMPK5 in ABA signaling were investigated. ABA treatment induced the increases in the expression of ZFP182, OsMPK1 and OsMPK5, and the activities of superoxide dismutase (SOD) and ascorbate peroxidase (APX) in rice leaves. The transient gene expression analysis and the transient RNA interference (RNAi) analysis in protoplasts showed that ZFP182, OsMPK1 and OsMPK5 are involved in ABA-induced up-regulation in the activities of SOD and APX. Besides, OsMPK1 and OsMPK5 were shown to be required for the up-regulation in the expression of ZFP182 in ABA signaling, but ZFP182 did not mediate the ABA-induced up-regulation in the expression of OsMPK1 and OsMPK5. These results indicate that ZFP182 is required for ABA-induced antioxidant defense and the expression of ZFP182 is regulated by rice MAPKs in ABA signaling.

A Novel Mitogen-Activated Protein Kinase Gene in Maize (Zea mays),ZmMPK3,is Involved in Response to Diverse Environmental Cues

In search for components of mitogen-activated protein kinase (MAPK) cascades in maize (Zea mays) involved in response to abscisic acid (ABA) stimulus,a novel MAPK gene,ZmMPK3,from ABA-treated maize leaves cDNA was isolated and characterized.The full length of the ZmMPK3 gene is 1 520 bp and encodes a 376 amino acid protein with a predicted molecular mass of 43.5 kD and a pI of 5.83.ZmMPK3 contains all 11 MAPK conserved subdomains and the phosphorylation motif TEY.Amino acid sequence alignment revealed that ZmMPK3 shared high identity with group-A MAPK in plants.A time course (30–360 min) experiment using a variety of signal molecules and stresses revealed that the transcripts level of ZmMPK3 accumulated markedly and rapidly when maize seedlings were subjected to exogenous signaling molecules: ABA,H2O2,jasmonic acid and salicylic acid,various abiotic stimuli such as cold,drought,ultraviolet light,salinity,heavy metal and mechanical wounding.Its transcription was also found to be tissue-specific regulated.Here,we show that ABA and H2O2 induced a significant increase in the ZmMPK3 activity using immunoprecipitation and in-gel kinase assay.Furthermore,the results showed that the ZmMPK3 protein is localized mainly to the nucleus.These results suggest that the ZmMPK3 may play an important role in response to environmental stresses.

OsDMI3 Is a Novel Component of Abscisic Acid Signaling in the Induction of Antioxidant Defense in Leaves of Rice

Ca2+ 和 calmodulin (凸轮) 被看了抗氧化剂防卫到在 abscisic 酸(骆驼毛的织物) 的一个重要角色导致了的玩。然而， Ca2+/CaM-dependent 蛋白质 kinase (CCaMK ) 是否涉及这个过程，是未知的。在现在的学习，米饭 CCaMK 的角色， OsDMI3，在导致骆驼毛的织物的抗氧化剂，防卫在米饭(Oryza sativa ) 的叶子被调查植物。有骆驼毛的织物， H2O2，和聚乙烯乙二醇(木钉) 的处理导致了 OsDMI3 和 OsDMI3 的活动的表示，并且 H2O2 在水应力下面为表示和 OsDMI3 的活动的导致骆驼毛的织物的增加被要求。Subcellular 本地化分析证明 OsDMI3 位于原子核，细胞质，和血浆膜。在米饭原物和在米饭原物的 OsDMI3 的 silencing 显示出的 RNA 干扰(RNAi ) 的 OsDMI3 的短暂表示的分析那 OsDMI3 为表示和 superoxide dismutase (草皮) 和过氧化氢酶(猫) 的活动的导致骆驼毛的织物的增加被要求。进一步，氧化损坏由木钉的更高的集中导致了， H2O2 在 OsDMI3 的异种被加重。而且，在原物和 OsDMI3 的异种的 OsDMI3 的 RNAi silencing 的分析证明 H2O2 累积的高水平要求在骆驼毛的织物发信号的 OsDMI3 激活，而是起始的 H2O2 生产导致了由骆驼毛的织物不依赖于在米饭植物的叶子的 OsDMI3 的激活。我们的数据表明 OsDMI3 是在在米饭的导致骆驼毛的织物的抗氧化剂防卫的一个重要部件。

Cell wallβ-1,4-galactan regulated by the BPC1/BPC2-GALS1 module aggravates salt sensitivity in Arabidopsis thaliana

Salinity severely reduces plant growth and limits agricultural productivity.Dynamic changes and rearrangement of the plant cell wall is an important response to salt stress,but relatively little is known about the biological importance of specific cell wall components in the response.Here,we demonstrate a specific function ofβ-1,4-galactan in salt hypersensitivity.We found that salt stress induces the accumulation ofβ-1,4-galactan in root cell walls by up regulating the expression of GALACTAN SYNTHASE 1(GALS1),which encodes aβ-1,4-galactan synthase.The accumulation ofβ-1,4-galactan negatively affects salt tolerance.Exogenous application of D-galactose(D-Gal)causes an increase inβ-1,4-galactan levels in the wild type and GALS1 mutants,especially in GALS1 overexpressors,which correlated with the aggravated salt hypersensitivity.Furthermore,we discovered that the BARLEY B RECOMBINANT/BASIC PENTACYSTEINE transcription factors BPC1/BPC2 positively regulate plant salt tolerance by repressing GALS1 expression andβ-1,4-galactan accumulation.Genetic analysis suggested that GALS1 is genetically epistatic to BPC1/BPC2 with respect to the control of salt sensitivity as well as accumulation ofβ-1,4-galactan.Taken together,our results reveal a new regulatory mechanism by whichβ-1,4-galactan regulated by the BPC1/BPC2-GALS1 module aggravates salt sensitivity in Arabidopsis thaliana.

Involvement of Protein Phosphorylation in Water Stress-induced Antioxidant Defense in Maize Leaves

Using pharmacological and biochemical approaches,the role of protein phosphorylation and the interrelationship between water stress-enhanced kinase activity,antioxidant enzyme activity,hydrogen peroxide(H2O2) accumulation and endogenous abscisic acid in maize(Zea mays L.) leaves were investigated.Water-stress upregulated the activities of total protein phosphorylation and Ca2+-dependent protein kinase,and the upregulation was blocked in abscisic acid-deficient vp5 mutant.Furthermore,pretreatments with a nicotinamide adenine dinucleotide phosphate oxidase inhibitor and a scavenger of H2O2 significantly reduced the increased activities of total protein kinase and Ca2+-dependent protein kinase in maize leaves exposed to water stress.Pretreatments with different protein kinase inhibitors also reduced the water stress-induced H2O2 production and the water stress-enhanced activities of antioxidant enzymes such as superoxide dismutase,catalase,ascorbate peroxidase and glutathione reductase.The data suggest that protein phosphorylation and H2O2 generation are required for water stress-induced antioxidant defense in maize leaves and that crosstalk between protein phosphorylation and H2O2 generation may occur.

OsHK3 is a crucial regulator of abscisic acid signaling involved in antioxidant defense in rice

In this study, the role of the rice(Oryza sativa L.)histidine kinase Os HK3 in abscisic acid(ABA)-induced antioxidant defense was investigated. Treatments with ABA, H2O2,and polyethylene glycol(PEG) induced the expression of Os HK3 in rice leaves, and H2O2 is required for ABA-induced increase in the expression of Os HK3 under water stress. Subcellular localization analysis showed that Os HK3 is located in the cytoplasm and the plasma membrane. The transient expression analysis and the transient RNA interference test in rice protoplasts showed that Os HK3 is required for ABA-induced upregulation in the expression of antioxidant enzymes genes and the activities of antioxidant enzymes. Further analysis showed that Os HK3 functions upstream of the calcium/calmodulin-dependent protein kinase Os DMI3 and the mitogen-activated protein kinase Os MPK1 to regulate the activities of antioxidant enzymes in ABA signaling. Moreover, Os HK3was also shown to regulate the expression of nicotinamide adenine dinucleotide phosphate oxidase genes, Osrboh B and Osrboh E, and the production of H2O2 in ABA signaling. Our data indicate that Os HK3 play an important role in the regulation of ABA-induced antioxidant defense and in the feedback regulation of H2O2 production in ABA signaling.