Auxin-responsive Gene PpIAA5-ARF8 On Peach Fruit Ripening And Softening

Peach(Prunu spersica L.)is considered as a model material for the study of Rosaceae fruit trees because of its wide cultivation area,high yield in China and clear genetic background.Peach is a typical respiration climacteric fruit,the ripening consequence is softening quickly,and it is extremely easy infected by pathogenic microorganisms,which shortens the shelf life,causes economic losses,and limits the development of peach industry.Hormone regulates the ripening and softening process of peach fruit,and auxin is an important regulatory hormone.The physiological process regulated by auxin is mediated by auxin signal transduction system.Aux/IAA and ARF transcription factors are the key regulators of auxin signaling pathway,which have been widely studied in tomato fruit ripening,but their regulation on peach fruit ripening is rarely reported.Previous studies in our laboratory found that some genes of Aux/IAA and ARF family may be involved in peach fruit ripening.In order to explore the regulatory effects of Aux/IAA and ARF on peach fruit ripening,this study explored the possibility of PpIAA5 participating in peach fruit ripening and softening process,clarified the strong interaction between PpIAA5 and PpARF8,and preliminarily confirmed that PpARF8 promoted peach fruit ripening.The results are as follows:1.The differentially expressed genes related to auxin signal transduction and synthesis and peach fruit ripening were obtained by transcriptome sequencing and integrated genomic database analysis of’Wan No.24’ peach fruits at different ripening stages.The relative expression level of PpIAA5/PpARF8 in peach increased in ripening stages.PpGH3.1,PpSAUR50,PpYUCCA10 and PpYUCCA6,four genes related to auxin signal transduction and synthesis,all showed a significant upward in the late stage of fruit ripening,and the genes PpERF4 and PpSAM related to ethylene signal transduction and synthesis also increased significantly in the late ripening stage of peach fruit.2.Combined with the previous laboratory research and RT-qPCR results,it was preliminarily determined that PpIAA5 gene may be involved in the ripening and softening process of peach fruit.After transient overexpression of PpIAA5 in peach fruit,the gene expression of PpSAUR50,PpGH3.1and PpYUCCA2/6/10 related to auxin signal transduction was significantly lower than that in the control group.The expression of some enzymes related to cell wall degradation and ethylene synthesis-related genes in peach fruit was affected,in which the expression of PpPA,PpPG and PpACO1 was significantly lower than that of the control group,indicating that PpIAA5 inhibited the expression of genes related to ripening and softening of peach fruit,which may be an inhibitory factor.3.The protein PpARF8,interacting with PpIAA5 was obtained by yeast two-hybrid and yeast library screening experiment.The interaction between PpIAA5 and PpARF8 protein was confirmed by bimolecular fluorescence complementary experiment.4.After transient overexpression of PpARF8 in peach fruit,the expression of cell wall degradation related genes PpEXP2,Ppβ-GAL,PpGLU,PpPA,PpPG and ethylene biosynthesis gene PpACO1 were significantly up-regulated.After transient transformation of strawberry and tomato with overexpression of PpARF8,the fruit matured earlier,while the fruit ripening of strawberry and tomato was inhibited after silencing PpARF8 gene.It was preliminarily confirmed that PpARF8 promoted the ripening and softening of peach fruit.