Functional Analyses Of GhHDA5 And GhHDA6 Genes In Early Maturity Of Upland Cotton

Cotton is an important fiber crop and plays an important role in China's agricultural economy.Cotton early maturity is a complex agronomic trait and one of the important objectives of cotton breeding.At present,most of the reports on cotton focus on cotton fiber quality and yield,while there are few studies on cotton early maturity.This study aims to identify the genes related to cotton precocity and analyze their functions.The main conclusions are as follows:1.On the basis of previous research in our lab,we selected RIL174 from the recombinant inbred line population as the female parent and G2005 as the recurrent parent to construct a BC₁F₂ secondary isolation population containing 828 individual plants.The distribution of the flowering time of this population showed normal distribution.Thirteen pairs of polymorphism SSR markers were screened in the vicinity of the candidate regions,and the genotypes of BC₁F₂population were identified.QTL mapping was performed using additive-complete interval mapping.A major QTL(q FT-D03)was detected on chromosome D03,located between 32.8 and 34.82 Mb,with a LOD value of 17.57,explaining 9.87%of phenotypic variation.Functional annotation and expression pattern analysis of 68 genes in the QTL region were carried out,and a flower-related gene Gh HDA6 was selected.Tissue expression pattern analysis showed that Gh HDA6 gene had a high expression level in flower organs,and there were significant differences in flower bud differentiation stages between the two parents.The flowering time of overexpressed transgenic Arabidopsis was earlier than the wild type,while the virus-induced Gh HDA6silenced lines showed a late flowering phenotype compared with the control VA plants.Two genes,Gh MSI4 and Gh NF-YC2,were identified to interact with Gh HDA6 by screening AD plasmid library of yeast associated.The expression patterns of these two genes were similar,and they were differentially expressed in early and late maturity cotton materials,suggesting that the two genes might interact with Gh HDA6 gene to regulate cotton flowering time.2.In order to identify QTLs and genes related to the the node of the first fruiting branch of cotton,a BC₄F₂ population consisting of 278 individual plants was constructed by using the recombinant inbred line RIL182 as the base material and G2005 as the recurrent parent.The node of the first fruiting branch of BC₄F₂ population was investigated at the budding stage,and two DNA mixed pools were selected from the extreme individual plants.QTL on the node of the first fruiting branch were identifed by BSA sequencing technology.Two key QTL located in the hot spots were identified by QTL-Seq and co-localization methods.Two genes,Gh APL and Gh HDA5,were identified by expression pattern analysis and VIGS assay.They were significantly different in flower bud differentiation between these two parents.Compared with the control VA plants,the Gh APL and Gh HDA5 silenced plants showed higher NFFB and delayed flowering time.3.In this study,two histone deacetylases Gh HDA6 and Gh HDA5 were identified to be associated with early maturity of cotton,indicating that RPD3-type deacetylases play an important role in early maturaty of cotton.A total of 108 RPD3 genes were detected in 9 species by genome-wide identification.According to the classification of Arabidopsis,these genes are divided into four subgroups.By analyzing the exon-intron structure and conserved motif of 54 cotton RPD3 genes,there were significant differences among the four subfamilies,but they were highly conserved in the same branch.The number and chromosomal distribution of RPD3 gene in diploid and tetraploid cotton cultivars were relatively conserved.The analysis of gene expression patterns showed that most Gh RPD3 genes were highly expressed in flower organs,and the expression of RPD3 gene could be induced by four abiotic stresses,for example,low temperature,high temperature,PEG and Na Cl.At the stage of flower bud differentiation,the expression level of five RPD3 genes in early maturity cotton was significantly higher than that in late maturity cotton.In addition,Gh RPD3 gene can respond to treatment of exogenous hormones Me JA and ABA.These results laid a foundation for analyzing the genetic mechanism of early maturity and breeding early maturity varieties of cotton in the future.