Screening And Functional Verification Of Candidate Genes For Upland Cotton Precocious Characters

Upland cotton(Gossypium hirsutum L.)is one of the most important cash crops,offering people with natural fiber andindustrial or edible oil,and has vital status in fodder and raw materials such as fine chemicals.With the reduction of arable land area,the contradiction between grain and cotton is becoming more and more serious,and the benefit of cotton planting by farmers is low,which leads to the annual decrease of cotton planting area in China.The short-season cotton,with short growth period and early maturity,is suitable for rotation of oilseed rape or wheat.Additionally,it is considered to be the effective breakthrough to solve the current cotton planting dilemma.The flowering time has a great influence on the growth period of short-season cotton.Understanding the flowering mechanism of cotton is of vital importance for breeders to choose suitable materials and even for the precise design breeding.In this study,the candidate genes in the flowering correlation QTL(qFT-D3-3 and qFT-15-D03-3)were screened by genomic functional annotation and fluorescence quantitative PCR.The relevant functions of candidate genes were preliminarily knowed by the methods of bioinformatics analysis,the transgenic of Arabidopsis thaliana and gene silencing induced by virus.The conclusions were as follows:1.The expression of GhSUVH5 gene in zhong 751213 with early flowering was higher than that in Lumianyan 28 with late flowering at the stages of 2 leaves,3 leaves,4 leaves,5 leaves.The expression of GhEMF2 gene in late flowering material,Lumianyan 28,was higher than that in the early flowering material,zhong 751213,in the bud of 4 leaves and 5 leaves.2.The main structural domains of GhSUVH5 protein included SAD/SRA,Pre-SET,SET,and was a kind of lysine methyltransferase,and it was involved in DNA methylation identification and chromatin ubiquitination.The GhEMF2 protein contained the special structural domain of the Polycomb Group,VEFS-box,which could be used to remodel the heterochromatin by forming a complex with other Polycomb proteins.3.Over-expression of GhSUVH5 in Arabidopsis promoted flowering and made rosette leaves reduction under long-day conditions.Over-expression of GhEMF2 in Arabidopsis promoted flowering and made rosette leaves reduction under long-day conditions.Over-expression of GhEMF2 in Arabidopsis appeared the shade-avoidance responses under short-day conditions,and the principal roots were shorter than that in the wild type under both long-day and short-day conditions4.The expression of GhEMF2 endogenous gene decreased by 20% to 30% after being inoculated CLCRV-EMF2 vector in cotton.The budding stage and flowering stage were shorter and the number of branches was also less than that of the control section.It showed that the GhEMF2 played roles of inhibiting the induction of flower formation and reproductive growth.