Identification Of SAUR Gene Family And Preliminary Functional Analysis Of Several SAUR Genes In Loquat

Loquat belongs to the genus Eriobotrya Lindl in Maloideae,Rosaceae whose fruit size is an important quality trait and an important basis for the formation of yield.Therefore,it has always been the focus of research in the loquat industry,in order to break through the current situation of low production and high production cost.Studies have shown that cell number and cell size are the two core factors that determine fruit size.Based on the research results of the effect of these two core elements on the size of loquat fruit,It is shown that the contribution of cell size to the growth of loquat fruit is greater than the number of cells.At the same time,the sister lines ZP44 and ZP65,which retain a pair of fruit size extreme differences,were screened in the crossbreeding breeding population.Using the RNA samples of the five periods of the two materials for RNA-seq,it was found that the expression changes of auxin signal transduction genes,especially multiple SAURs,were significantly correlated with cell expansion and fruit size.SAUR is one of the early growth genes of auxin and is unique to plants.At present,SAUR gene has been reported in Arabidopsis,Malus,cotton,citrus,etc.,but has not been studied in the loquat.this study identified and analyzed the SAUR gene family of loquat,EjSAUR1,EjSAUR23,EjSAUR33 and EjSAUR38 were cloned and sequenced.The ZP65 and ZP44 lines were used as materials to compare physiological and biochemical characteristics and cytological characteristics.The expression patterns of EjSAUR1,EjSAUR23,EjSAUR33 and EjSAUR38 in different tissues and fruit development were analyzed by q PCR.The response patterns of EjSAUR1,EjSAUR23,EjSAUR33 and EjSAUR38 under IAA conditions were analyzed.After fruit silencing,the traits and cytological characteristics of the matured fruit were compared and analyzed.The expression levels of EjSAUR1,EjSAUR23,EjSAUR33 and EjSAUR38 were also analyzed.Furthermore,functional analysis of EjSAUR23,EjSAUR33 and EjSAUR38 were performed in Arabidopsis.The main findings are as follow:(1)Using the Arabidopsis 72 SAUR protein sequences for Blast P alignment in the genomic database(unpublished),57 SAUR gene sequences were detected.These gene CDS range from 267 to 735 bp and the predicted protein is 88-244 aa.A comprehensive analysis of the SAUR gene family in terms of subcellular localization,EjSAUR position distribution on chromosomes,EjSAURs phylogeny and expression profiling.The results showed that 47 SAUR genes were distributed on 11 chromosomes,and 10 SAUR genes failed to locate on the chromosome.80.9% of EjSAURs clustered on the loquat chromosome,suggesting that tandem repeat genes may be the primary mechanism for this family to amplify.Expression profiling indicated that the EjSAURs has different expression patterns in different organs,some of which exhibit tissue-specific expression patterns.The above results provide a framework for further study of the EjSAUR gene.(2)ZP65 and ZP44 lines were used as experimental materials to observe the growth and development of the two materials and the cell size and quantity in their corresponding periods.At the same time,q PCR was used to analyze the expression patterns of several SAUR genes in different tissues and fruits at different stages.The results showed that except EjSAUR1,EjSAUR23,EjSAUR33 and EjSAUR38 are mainly expressed in fruit,and their expression patterns in fruit at different stages are closely related to fruit cell expansion.These results may suggest that the expression levels of EjSAUR23,EjSAUR33 and EjSAUR38 may be involved in the regulation of cell expansion of loquat fruit.(3)After exogenous IAA treatment,the expression of EjSAUR1,EjSAUR23,EjSAUR33 and EjSAUR38 in the fruit was up-regulated,and the expression of EjSAUR23,EjSAUR33 andEjSAUR38 was up-regulated,but the expression of EjSAUR1 was decreased,which proved that IAA could promote the expression of EjSAUR23,EjSAUR33 and EjSAUR38.Subsequently,further observation of Ripe fruit traits and corresponding pulp sections showed that IAA couldcause up-regulation of the expression levels of EjSAUR23,EjSAUR33,and EjSAUR38 topromote cell expansion.(4)VIGS experiment was carried out in the early stage of fruit enlargement.After silencing treatment,the expression levels of EjSAUR1,EjSAUR23,EjSAUR33 and EjSAUR38 were decreased.At the same time,the fruit was silenced was smaller.The paraffin section analysis showed the area of the corresponding fruit cells is also smaller.Therefore,it is speculated that the down-regulation of EjSAUR expression makes the pulp cells smaller.In addition,overexpression of EjSAUR23,EjSAUR33 and EjSAUR38 in Arabidopsis enlarged the leaves,further providing evidence that EjSAUR23,EjSAUR33,and EjSAUR38 may may be involved in cell expansion.