Abstract:

β-ketoacyl-CoA synthase（KCS）is a rate-limiting enzyme in the synthesis of very long chain fatty acids. Identification and analysis of KCS gene family lays a foundation for revealing the specific function in controlling the wax characters of Chinese cabbage（Brassica rapa）. The members of Chinese cabbage KCS gene family were identified by bioinformatics method,and their genetic relationship,protein physical and chemical properties,chromosome location,collinearity,gene structure,protein conserved domain structure and gene expression pattern were analyzed. A total of 32 BrKCS gene members were identified from the whole genome of Chinese cabbage. Phylogenetic analysis indicated that these BrKCS genes were divided into 4 subgroups,which were unevenly distributed on 10 chromosomes. The amino acid length and molecular weight of BrKCS proteins ranged from 181 to 755 aa and 20.54 to 84.83 kD,respectively. Collinearity analysis showed that 7 family members such as BrKCS5,BrKCS8 and BrKCS13 doubled with the BrKCS gene of Arabidopsis,and one family member（BrKCS9）tripled. Gene structure analysis showed that the number and location of exons of amino acid sequences encoded by different members were different. Transcriptome analysis showed that BrKCS5,BrKCS6b and BrKCS10b genes played an important role in controlling waxy characters in different organs/tissues of Chinese cabbage,especially in flower organs. qRT-PCR analysis verified the reliability of transcriptome data. In conclusion,a total of 32 BrKCS were identified from the whole genome of Chinese cabbage,of which three genes were highly expressed and significantly different in waxy near-isogenic lines,laying a foundation for analyzing the molecular mechanism of BrKCS gene in controlling Chinese cabbage wax traits.

Key words: Brassica rapa, KCS gene family, wax, polyploidization, expression analysis