Functional Characterization On An Abscisic Acid Receptor Family Gene TaPYR1 In Wheat In Mediating Plant Tolerance To Drought Stress

Through interaction with abscisic acid(ABA)molecules that are induced by osmotic stresses,the ABA receptors involve the mediation of the ABA signaling transduction and play critical roles in regulating the drought stress tolerance in plants.In this study,TaPYR1,an ABA family gene in wheat that showed differential expression in our previous transcriptome analysis,was subjected to characterize on molecular property,expression patterns upon drought stress condition,and its function in mediating plant adaptation to drought stress.The main results are as follows:1.The wheat ABA receptor gene TaPYR1 was 840 bp in length with 636 bp to be open reading frame.TaPYR1 protein has a molecular weight of 22.621 kD and an isoelectric point(PI)of 4.97.TaPYR1 shares high similarities to its plant counterparts at amino acid level.The coding protein is highly similar in sequence composition to some homologous proteins of plant species,containing the conserved region of the SRPBCC superfamily of the PYR family protein(44-192 aa).In addition,subcellular localization test of the protein encoded by this gene revealed that TaPYR1 was localized to the plasma membrane after endoplasmic reticulum sorted,which suggested that it is involved in the transmission ABA and specific ABA signals after binding ABA at this position.2.The TaPYR1 gene showed an obvious drought-induced expression pattern in wheat roots and leaves.Under normal growth conditions,the number of TaPYR1 transcripts in wheat roots and leaves was low;under drought treatment,TaPYR1 expression was up-regulated,which appeared within 48 h,The number of transcripts continued to increase with the progress of the treatment,and the expression level peaked at 48 h under drought stress.The expression of TaPYR1 was induced in both roots and leaves upon drought treatment,with the highest expression levels at 48 h after the treatment.3.Transgene analysis on TaPYR1 was performed to assess the gene function in mediating plant drought tolerance.Compared with wild type(WT),the tobacco lines overexpressing TaPYR1 conferred plants enhanced growth vigor and increased fresh and dry weight under drought stress treatment.Transgene analysis on TaPYR1 was performed to assess the gene function in mediating plant drought tolerance.With the progress of drought treatment,the stomata openings of the transformed strains and WT continued to decrease.However,compared with WT,the stomata closing rate of the Sen.Tobacco strain(Sen 1)was accelerated,while that of the Antisense strain(Anti 1)was slower.Compared with wild type(WT),the tobacco lines overexpressing TaPYR1 conferred plants enhanced growth vigor and increased fresh and dry weight under drought stress treatment.In addition,the transgenic lines with TaPYRl overexpression also increased photosynthetic function,enhanced activities of cellular antioxidant enzymes,and elevated the contents of osmolytes(i.e.,proline and soluble sugar)of plants once challenged by drought condition.The regulation of tapyrl on plant growth and dry quality under drought stress is closely related to the regulation of stomatal movement and photosynthetic carbon assimilation.4.Under drought stress,the regulation of TaPYR1 on cell protective ability is related to the transcription regulation of cell protective enzyme family gene and ABA receptor family gene.Compared with WT,the expression of NtSOD2,NtCAT and NtPOD1;3,NtPOD1;4 and NtPOD4 in Sen lis significantly up-regulated;the expression of NtPYL8 is significantly down regulated,and the expression of NtPYL12 is significantly up regulated;the expression of NtSRK2A-2 and NtSAPK3 is significantly up regulated,and the expression of NtSPK3;23,The expression of NtSPK7 was significantly down regulated.5.Sequencing the transcriptome analyses revealed that compared with WT,there were 17197 differential genes in TaPYRl overexpressing tobacco plants under drought treatment,including 8261 genes to be up-regulated and 8936 genes downregulated.These differential genes are associated with specific response in ABA signaling processes and are enriched in plant signal transduction-associated pathways.Our investigation indicated that TaPYR1 is response to drought stress signaling and plays an important role in regulating plant drought adaptation by improving the associated physiological processes.