Combined gene family characterization and RNA-Seq to study the response of β-ketoacyl-CoA synthase to abiotic stress in rice (Oryza sativa L.)

β-ketoacyl-CoA synthase is a key enzyme in the biosynthesis of over-long-chain fattty acids; thus, it plays a crucial role in plant resistance to stress. Herein, 33 OsKCSs were classified into five subfamilies based on phylogenetic analysis and domain structure in rice. Nonsynonymous to synonymous substitution ratio (Ka/Ks) analysis showed that duplicated genes were possibly under strong purifying selection pressure. Cis-element analysis revealed that OsKCSs may be regulated by different transcription factors. SNP distribution of OsKCSs in 295 germplasm accessions seemed associated with functional disparity under environmental stress. Additionally, 10 of the 33 OsKCSs were not expressed in different rice tissues. RNA-Seq and qRT-PCR analysis demonstrated that seven OsKCSs (OsKCS5, OsKCS6, OsKCS14, OsKCS15, OsKCS4, OsKCS30, and OsKCS21) had significantly different expression levels under 0.5% NaCl, 0.5% Na2CO3, and a 10-day incubation at 17 °C. Our results provide a solid foundation for understanding the roles of OsKCS genes and the mechanism by which they regulate stress resistance.