Functional Analysis Of OsLEA5 In Response To Drought And Salt Stresses And Its Co-regulation With ZFP36 In Seed Germination In Rice

The accumulation of the plant hormone ABA(abscisic acid)plays important roles in the response to abiotic stress(drought,high salt,etc).ABA induced by water stress can promote the antioxidant defense to enhance plant tolerance.Previous studies have revealed that ZFP36(zinc finger transcription factor)is involved in ABA-induced antioxidant defence.For further study the function of ZFP36 in ABA-induced antioxidant defense,we screened a protein,using the full-length of ZFP36 as bait by the yeast two hybrid approach,named OsLEA5.OsLEA5 belongs to the atypical late embryogenesis abundant group 5C from Oryza Sativa L and is involved in ABA-induced antioxidant defenses.In this review,mainly using RNAi interference materials as a supplement to the previous study and made a preliminary exploration about the mechanism of seed germination.The activities of antioxidant enzymes were significantly lower than that of wild type,while the MDA content and membrane leakage rate were increased under the treatment with PEG and NaCl,which indicated that OsLEA5 is involved in the stress.In addition,the root length of over-expression plants were shorter than wild type after treated with ABA,while the interference plants were insensitive to ABA compared with wild type.The ABA content were detected by UPLC and RT-PCR were used to detect the transcript levels of ABA synthesis,metabolism and dehydrin genes.The results showed that OsLEA5 overexpression plants had higher transcript levels of ABA synthesis and dehydrin-related genes than wild-type plants.While the interference plants showed the opposite results.Overexpress the OsLEA5 can enhance the ABA content and interference plants had lower ABA content compared with control under PEG and NaCl treatment The above results indicate that ABA participates in water stress by regulating the expression of OsLEA5,and OsLEA5 can increase the level of ABA in vivo by up-regulating ABA biosynthesis genes and down-regulating ABA degradation genes to achieve antioxidant protection.To explore the role of OsLEA5 and ZFP36 in seed germination,by ChIP(chromatin immunoprecipitation)-seq results,we found that ZFP36,a rice zinc finger transcription factor,could directly bind to the promoter of OsAPXl,and act as a transcriptional activator of OsAPX1 promoter.GUS experiments demonstrated that ZFP36 could interact with a late embryogenesis abundant protein OsLEA5 to co-regulate the promoter activity of OsAPXl.The seed germination is highly inhibited in ZFP36 overexpression plants under ABA treatment,while the RNA interference(RNAi)mutant of OsLEA5 rice seeds were less sensitive to ABA,and exogenous ASC(ascorbate acid)could alleviate the inhibition induced by ABA.Moreover,by LUC and qRT-PCR experments found two homologue of OsLEA5(5C700,short for Os05g0526700 and 5C300,short for Os05g0584300)which were induced by ABA also interacted with ZFP36 separately;interestingly,the nucleus-located 5C700 could also act as a co-activator of ZFP36 to modulate OsAPX1 while 5C300 which was ABA-induced down expressed played as an ABA-induced inhibitor of ZFP36 to regulate OsAPX1.Hence,we summarized that OsLEA5 participates in the ABA-mediated antioxidant defense to function in drought and salt stress response in rice,and 5C subgroup of LEAs contribute to play co-regulators of the transcription factor ZFP36 to promote the seeds germinate which inhibit by ABA.