Function Analysis Of Early Auxin-responsive Gene MdSAUR6 In Apple

Apple(Malus domestica)is one of the mainstream fruits in China,with high nutritional and commercial value,and is widely planted nationwide.The root system constitutes the underground part of the apple plant.It affects the aboveground growth by absorbing water,mineral nutrients and synthesizing endogenous hormones.Its good growth is extremely important for improving the resistance of fruit trees,ensuring the quality and high yield of fruit.SAURs(Small Auxin Up RNA)are early auxin response gene,which exists in many plants and encodes a specific small molecular protein in plant kingdom.At present,SAURs gene has been identified and cloned in soybean,maize,Arabidopsis and other plants.In this study,MdSAUR6 gene was obtained from apple by RT-PCR technology,and its expression regulation mode was analyzed.Transgenic plants with overexpression of MdSAUR6 were obtained by Agrobacterium tumefaciens-mediated leaf-disk method.The potential role of MdSAUR6 in regulating apple root growth was explored through the analysis of root phenotype and transcriptome sequencing of transgenic apple.The main research results are as follows:(1)The MdSAUR6 gene was successfully cloned from the apple genome.The MdSAUR6 gene has a total length of 519 bp and encodes 172 amino acids,containing the conservative domain SSD region of the SAUR gene family.The results of tissue organ specific expression analysis showed that the MdSAUR6 gene was expressed in the root,stem,and leaf of apple,with high expression in the root tissue and weak expression in the stem and leaf.The expression analysis of MdSAUR6 under hormone treatment showed that MdSAUR6 can be induced by hormones IAA and ABA in a short time,suggesting that MdSAUR6 may participate in the process of plant hormone signal transduction.(2)The overexpression vector p PZP211-MdSAUR6 was successfully constructed.The wild type ’Gala’ plantlets were genetically transformed using Agrobacterium tumefaciens mediated leaf disk method.After resistance screening,genomic DNA amplification,and quantitative PCR detection,a total of 5 overexpression apple transgenic lines were obtained.(3)Preliminary analysis of the phenotype of transgenic apple tissue-cultured seedlings with MdSAUR6 gene showed no significant phenotypic changes in the growth potential of wild-type WT and transgenic plants.Scanning of the roots of wild-type WT and transgenic plants revealed no significant changes in root length,surface area,number of root tips,root volume,and average root diameter between MdSAUR6 overexpressed tissue-cultured seedlings and wild-type.(4)The transcriptome sequencing analysis of transgenic plants overexpressing MdSAUR6 and control plants using RNA-Seq technology showed that a large number of differentially expressed genes were enriched in plant hormone transduction pathways,MAPK cascade signaling pathways,and amino acid metabolism pathways.It is speculated that the MdSAUR6 gene may participate in regulating the growth of apple plants at the molecular level.