Analysis And Functional Identification Of TaPYL Gene Family In Wheat

Wheat is one of the leading food crops in China,however its production is constrained by abiotic stresses,which seriously threatens food security.The clarification of regulation mechanism about stress tolerance,as well as the discovery and utilization of excellent genetic resources,greatly promoted the wheat genetic improvement.As reported in Arabidopsis and rice,PYL family genes of ABA receptors play important roles in ABA signaling pathway,which induce a series of physiological responses to participate in defense against abiotic stress.The related studies are less reported in wheat.In this study we conducted comparative genomics,association analysis,and molecular biology methods to identify wheat PYL family members at the genome-wide level,and to screen important functional members through positive selection analysis,gene expression,and genetic transformation.Allelic variation,and development of molecular markers,to provide new genes and new markers for wheat molecular stress breeding.The main findings are as follows:1.According to the conserved domain,27 PYLs were identified in the wheat genome.They were distributed on all the chromosomes except chromosomes 5 and 6.Gene and protein structure analysis showed that no introns existed in TaPYLs except for TaPYL1 and TaPYL8,and the amino acid sequences were highly conserved.The TaPYLs were divided into 6 subgroups according to their evolution relationship.12 TaPYLs in GroupA and GroupB exhibited rapid evolution,with the ω values of 0.349 and 0.321,respectively.For GroupA,three sites(P>0.99)were identified to experience positive selection.Four main cis-acting elements were identified in the promoters of TaPYLs,involved in abiotic stress response,light response,hormone response and plant growth and development.RNA-seq expression profiles showed that TaPYL1,TaPYL2,TaPYL4 and TaPYL7 were constitutively expressed,whereas others showed tissue specificity.2.The qPCR results showed different response patterns of TaPYLs under drought and heat stress.TaPYL1,TaPYL3,TaPYL4,TaPYL5,and TaPYL6 showed highest expression level within 6 hours after drought stress,and then gradually returned to normal levels,while expression TaPYL2 decreased at the beginning and gradually recovered within 12 hours.Under heat stress,the expression levels of TaPYL1 and TaPYL2 were highest at 6 h,TaPYL3,TaPYL5,TaPYL6 and TaPYL9 were highest at 12 h,and TaPYL7 and TaPYL4 were down-regulated.Overexpression of TaPYL1 in Arabidopsis enhanced high temperature and drought tolerance,the survival rate after re-watering increased by 34% and 43%.The biomass of transgenics were significantly increased than controls under high temperature.3.TaPYL4 has been reported to enhance drought resistance and significantly improve water use efficiency in wheat.The diversity and haplotype distribution of TaPYL4 in Chinese wheat MCC were analyzed in this study.Based on the development of InDel and dCAPS markers,the candidate gene association analysis showed that TaPYL4-2AS contains 3 haplotypes in the promoter region,and PYL4-2AS-Hap-2 is the favorable haplotype,which can reduce plant height by 7~12 cm,increase the effective tiller number by 1 ~ 1.5 and the 1000-grain weight by 2 ~ 5 g in landraces,while reduce plant height by 1 ~ 4 cm in modern cultivars.There are two haplotypes in TaPYL4-2BL,the grains number were increased by 4 to 5 in PYL4-2BL-Hap-1,which is the favorable allele and was positively selected in wheat breeding.