Characterization of GhSERK2 and its expression associated with somatic embryogenesis and hormones level in Upland cotton

Somatic embryogenesis (SE) is one of the most important steps during regeneration of cotton, but the molecular mechanism of SE remains unclear. SOMATIC EMBRYOGENSIS RECEPTOR KINASE (SERK) gene is known to function in SE. A homolog GhSERK2 (accession number: JF430801) was cloned from Upland cotton and characterized for its functions in SE. GhSERK2 expressed in different tissues and showed higher expression level in floral organs than vegetative ones with the highest levels in ovule and anther. GhSERK2 expressed during SE with a high level at globular embryos stage. Upon treatment with indole-3-butytic acid (IBA), the transcription level of GhSERK2 was induced and promoted SE subsequently. A 2-day treatment of 2,4-dichlorophenoxyacetic acid (2,4-D) induced the expression of GhSERK2, but treatments of 2,4-D for longer periods sharply inhibited the GhSERK2 transcription level of embryogenic callus (EC). The levels of hormones, including 3-indoleacetic acid (IAA), abscisic acid (ABA), and brassinosteroid (BR), were increased in the initial calli induced from the over-expression of GhSERK2 cotton. Our results indicated that GhSERK2 expression was associated with induction of SE and closely related to hormone levels during tissue culture in Upland cotton, and the gene might play an important role in regeneration of cotton.