Effect Of Spraying Spermidine On The Flowering Of Flower Buds In 'Nagafu No.2' Apple And Identification And Analysis Of Polyamine Oxidase Gene Family

Difficulties in flowering of‘Fuji'apples severely restrict the development of the apple industry.Studies have shown that external application of polyamines?Polyamines,PAs?can induce the formation of flower buds,and spermidine?Spermidine,Spd?dominates in the process of flower bud differentiation,but no mechanism about the effect of Spd on apple flower formation Report.In order to study the effect of Spd on apple blossom,the flowering period;the endogenous polyamines in the top buds of short branches after spraying were measured,The content of endogenous hormones and the expression of genes related to polyamines,hormones and flower formation;the flower formation rate in the second year.Polyamine oxidase?PAO?,as a decomposing enzyme in the polyamine oxidation pathway,participates in PA terminal catabolism or reverse conversion,affects PA homeostasis and regulates plant growth and development.In this experiment,the biological information of apple PAO family members was systematically identified,the expression pattern of PAO gene after spraying Spd in different tissues was measured,and its possible role in PA steady state was predicted,providing a theoretical basis for further study of its gene function.The research results are as followsapple tree was treated with1.After exogenous spraying of Spd,the content of Put and Spd in the top buds of‘Nagafu No.2'apple short branches was significantly increased in the late stage of flower bud differentiation?60-80 days?,while the content of endogenous Spm was significantly reduced;The content of GA₃ decreased significantly in the late stage of flower bud differentiation?60-80 days?,the content of ABA increased significantly,and the changes of IAA and ZT content were not significant.In addition,during the physiological differentiation of flower buds,spraying Spd promoted the expression of the polyamine synthesis genes Md ADC1 and Md ODC1;significantly increased the expression level of the GA decomposition genes Md GA2ox2,up-regulated the transcription levels of the ABA synthesis genes Md NCED1 and Md NCED3;and promoted flower formation The transcription of related genes Md FD,Md FT and Md SOC1 significantly increased the flowering rate of‘Nagafu No.2'.2.Identified 8 apple PAO genes from the apple genome and divided them into 3subfamilies.It was found that members in the same subfamily had similar gene structure,protein structure and protein conserved motif distribution.The Md PAO gene promoter also contains multiple cis-acting elements,which are involved in the growth and development of apples.The GEO database shows that 8 Md PAOs have significant expression differences in different tissues and organs,and the expression of Md PAO4 in different varieties and organs is significantly higher than that of other family members.Using‘Nagafu No.2'apples as the material,RT-q PCR detection found that Md PAO3,Md PAO4,Md PAO5/6 and Md PAO8 had higher expression levels in flowers;Md PAO1/2 and Md PAO7 had higher expression in stems and fruits High expression level.After exogenous spraying Spd,in addition to Md PAO3,the transcription level of the remaining Md PAO increased significantly,indicating that Md PAO responded to Spd treatment.In summary,Spd treatment to promote‘Nagafu No.2'flowering is closely related to the expression of polyamines,hormone pathways and genes related to flower formation.And through bioinformatics analysis,the members of the Apple PAO gene family were systematically identified,and their functional characteristics were initially explored to provide a basis for further research on their functions.