Tracing the origin, evolutionary history, and biological functions of CKI genes: a focus on Gossypium spp

Abstract Background: Casein kinase I (CKI) is a kind of serine/threonine protein kinase highly conserved in plants and animals. Although molecular function of individual member of CKI family has been investigated in Arabidopsis, little is known about their origin and evolutionary history in the plant kingdom. Results: In this study, seven representative plant species (with a focus on cotton) are applied to study gene family evolution and characterize the origin of CKI genes. Three important insights were gained: (i) the ancestral CKI genes were traced back to 250 million years ago; the family expansion occurred in different plant species through independent genome duplication events; (ii) the CKI genes were classified into two types, on the basis of their structural characteristics; (iii) expression profile analysis revealed that cotton CKI genes had various expression patterns in different tissues and exhibited inducible expression in response to photoperiod (circadian clock), light signal and heat stress during cotton anther development. Conclusion: This study provides genome-wide insights into the evolutionary history of cotton CKI genes and lays a foundation for further investigation of their roles in specific developmental processes and/or environmental stress conditions.