Genome-wide identification and expression analysis of the KCS gene family in soybean (Glycine max) reveal their potential roles in response to abiotic stress

Abstract

Very long chain fatty acids (VLCFAs) are fatty acids with chain lengths of 20 or more carbon atoms, which are the building blocks of various lipids that regulate developmental processes and plant stress responses. 3-ketoacyl-CoA synthase encoded by the <i>KCS</i> gene is the key rate-limiting enzyme in VLCFA biosynthesis, but the <i>KCS</i> gene family in soybean (<i>Glycine max</i>) has not been adequately studied thus far. In this study, 31 <i>KCS</i> genes (namely <i>GmKCS1</i> - <i>GmKCS31</i>) were identified in the soybean genome, which are unevenly distributed on 14 chromosomes. These <i>GmKCS</i> genes could be phylogenetically classified into seven groups. A total of 27 paralogous <i>GmKCS</i> gene pairs were identified with their Ka/Ks ratios indicating that they had undergone purifying selection during soybean genome expansion. <i>Cis</i>-acting element analysis revealed that <i>GmKCS</i> promoters contained multiple hormone- and stress-responsive elements, indicating that <i>GmKCS</i> gene expression levels may be regulated by various developmental and environmental stimuli. Expression profiles derived from RNA-seq data and qRT-PCR experiments indicated that <i>GmKCS</i> genes were diversely expressed in different organs/tissues, and many <i>GmKCS</i> genes were found to be differentially expressed in the leaves under cold, heat, salt, and drought stresses, suggesting their critical role in soybean resistance to abiotic stress. These results provide fundamental information about the soybean <i>KCS</i> genes and will aid in their further functional elucidation and exploitation.