| Cotton fiber is a single-cell structure differentiated from ovule epidermal cells,and its development is a complex and orderly process involving a large number of genes involved in regulation.The biosynthesis of very long chain fatty acids（VLCFAs）has a significant role in promoting cotton fiber development.β-ketoacyl-Co A synthase（KCS）is a rate-limiting enzyme in VLCFAs biosynthesis and may affect the initiation and development of cotton linters.The low temperature of the environment severely restricts the yield and quality of cotton,but the molecular mechanism of temperature-affecting cotton fiber development is still unclear.This experiment aims to clarify the intrinsic relationship between low temperature,GbKCS14 and cotton fiber development,and provide a reliable theoretical basis for improving cotton quality,increasing cotton tolerance to low temperature and increasing cotton yield at low temperature.The main findings are as follows:（1）Experiments have shown that low temperature treatment（23℃）of 3-4 days post anthesis（DPA）after flowering can significantly affect the density and length of Gosspium barbadense NLD52,that is,high temperature promotes short pile elongation,and low temperature inhibits short pile elongation.On the other hand,the expression of most KCS genes in NLD52 ovules of Gosspium barbadense was inhibited by low temperature,while the expression of GbKCS14 was induced by low temperature.Bioinformatics analysis shows that GbKCS14 belongs to ELO-type KCS and is located as endoplasmic reticulum and Golgi apparatus.Analysis of tissue expression patterns showed that GbKCS14 gene was highly expressed in young leaves and ovules.（2）After low temperature treatment,the expression level of GbKCS14 in cotton ovule increased,the methylation abundance of promoter decreased,and the methylation level of CHH motif changed most obviously.A JMJ family histone lysine methyltransferase REF6 was further screened by the yeast single hybrid screening library,and its C2H2 domain was able to bind to the promoter at-370 to-359 bp.RT-qPCR results indicated that REF6 expression was also induced by low temperature.It indicated that REF6 may change the histone methylation status at a specific position on the GbKCS14 promoter at low temperature,which may affect the DNA abundance of its promoter and regulate its expression.（3）Analysis of the content of very long chain fatty acids in plant materials by GC-MS,the results showed that the content of eicosanic acid（C20:0）and tetracosanoic acid（C24:0）in the overexpressed lines compared with WT a significant increase indicates that GbKCS14 may be able to catalyze the synthesis of C20:0,C24:0.Exogenous application of C20:0 and C24:0 can promote the elongation of fibers by ovule in vitro culture experiments,which indicates that GbKCS14 plays an important role in cotton fiber development at low temperature. |
