Characterization of a ZmSERK gene and its relationship to somatic embryogenesis in a maize culture

A SOMATIC EMBRYOGENSIS RECEPTOR KINASE (SERK) gene has been linked to somatic embryogenesis in many plant species. We have developed a culture model that enabled investigation of the relationship between embryogenesis and the expression of various ZmSERK genes at different developmental stages and following treatment with hormones. The results indicate that auxin 2,4-dichlorophenoxyacetic acid (2,4-D) enhanced transcription activity of ZmSERK and promoted somatic embryogenesis. The cytokinin 6-benzyladenine (BA) inhibited embryogenesis and reduced the expression of ZmSERK1 and ZmSERK2, but it significantly increased the expression of ZmSERK3. The application of 2, 4-D and BA promoted the transcription of ZmSERK3 and inhibited that of ZmSERK1 and ZmSERK2, suggesting a fine regulation of embryogenesis by ZmSERK. The immature embryo at 12 and 15 days after pollination (DAP) showed the highest competence for embryogenesis and displayed the strongest ZmSERK gene expression, respectively. Based on these observations, we conclude that the expression profiles of ZmSERKs are closely related to hormone signaling and the developmental stages of the embryo during embryogenesis. ZmSERK1 and ZmSERK2 appear to play an important role in maintaining embryogenesis, while ZmSERK3 appears to have a dual role in embryogenesis by modulating its expression level.