Functional Analysis Of Rice ABA Receptors OsPYL1 And OsPYL9,and Maize BZIP Transcription Factors ZmbZIP36 And ZmbZIP81

PYR/PYL/RCAR proteins,which are located in nucleus and cytoplasm,act as ABA receptors in plant cell that can be recognized by their ligands and trigger downstream signaling pathway through direct interaction with ABA to regulate ABA-mediated gene expression and plant physiological response,bZIP transcription factors in plant belong to basic region/leucine zipper transcription factor family and play a vital role in diverse biological process such as plant defense response,photomorphogenesis and stress response.Several members of group A bZIP factors have been revealed to participate in ABA sigaling pathway.In order to explore the function of ABA receptors and bZIP transcription factors,we cloned the coding genes of two ABA receptors,OsPYL1 and OsPYL9 in rice,and two bZIP transcription factors,ZmbZIP36 and ZmbZIP81 in maize based on the rice and maize genome database.Gene expression in different growth and development stages of rice or maize and under different stress treatments were analyzed by Real-time PCR.Besides,Arabidopsis plants overexpressing the four genes were generated and their biological functions were assessed by phenotype analysis of the transgenic lines under different stress conditions,and gene and protein structure prediction by bioinformatics analysis.In addition,the function of OsPYL1 and OsPYL9 was further analysed by phenotype differences during the entire growth period by using mutant lines.The results indicated that OsPYL1 is located in chromosome 10 of rice,the coding region of which is 639 bp in length without intron,and encodes 212 animo acid residues.The expression of OsPYL1 was induced by drought and ABA treatment.Rice ospyll mutant showed decreased plant height,tiller number,seed setting rate,thousand seed weight and kernel number per spike,and Arabidopsis plants overexpressing OsPYL1 exhibited enhanced osmotic stress tolerance.It can be concluded that OsPYL1 plays a key role in rice growth and development,and can enhance plant stress resistance to a certain extent.Another gene OsPYL9 is located in chromosome 2 of rice.The coding region of OsPYL9 is 3582 bp in length with three exons and two introns,which encodes 204 animo acid residues.In contrast,OsPYL9 expression was inhibited by drought and ABA treatment.Rice ospyl9 mutant showed declined seed setting rate and thousand seed weight,and was accompanied by decreased flag leaf area.The germination of ospyl9 mutant seeds showed impaired resistance to osmotic strss and decreased sensitivity to ABA,and OsPYL9-overexpressing rabidopsis plants exhibited increased tolerance to osmotic stress.In conclusion,we can predict that OsPYL9 is imperative in plant stress tolerance,and may play important roles in maintaining rice yield by affecting flag leaf growth.ZmbZIP36 is located in chromosome 2 of maize encoding 295 animo acid residues,and ZmbZIP81 is located in chromosome 6 and encodes 254 animo acid residues.Both of them are group A bZIP transcription factor coding genes,which are induced by ABA,salt and drought treatment.Arabidopsis overexpressing ZmbZIP36 and ZmbZIP81 showed decreased sensitivity to ABA respectively compared with the wild type,but they performed differently when treated with salt stress.Overexpression of mbZIP36 made Arabidopsis plants more sensitive to salt,but ZmbZIP81 overexpression confered more resistance to salt.Additionally,ZmbZIP36 was found to be capable of interacting with ABA-responsive cis-elements(ABREs)that exist in promoter region of most ABA-responsive genes by yeast one-hybrid assay.It can be predicted that ZmbZIP36 and ZmbZIP81 may both play a role in ABA signaling pathway and plant stress response,while,perhaps owning different mechanisms.