Cloning and expression analysis of SERK1 gene in Diospyros lotus

Somatic embryogenesis receptor-like kinases (SERKs), a subfamily of receptor-like kinases, play important roles in response to abiotic stresses in addition to apomictic reproductive development in numerous plant species. The purpose of the present work was to determine if an ortholog of the SERK gene is present in the Diospyros lotus genome, isolate it and analyze its expression during embryogeny and abiotic stress. An ortholog of the SERK gene was isolated from the D. lotus genome, and designated as DlSERK1. The physical and chemical properties, protein structure, and evolutionary relationship of the DlSERK1 protein were analyzed by bioinformatics methods, and the expression of DlSERK1 gene during embryonic development and under low-temperature, salt, and drought stresses was examined through real-time quantitative PCR analysis. DlSERK1 contained 1,881 bp open reading frame encoding 626 amino acids, with a molecular mass of 69.18 kDa and pI of 5.34. DlSERK1 had strong hydrophilic property, signal peptide cleavage sites, and two transmembrane regions, indicating that DlSERK1 is a secretory protein. The secondary structure of DlSERK1 was consistent with the tertiary structure, both of which were dominated by random curls and alpha-helices. DlSERK1 had the typical structure of SERK proteins, and harbored multiple phosphorylation and glycosylation sites. Quantitative analysis showed that DlSERK1 was expressed during the embryonic development period, and the highest expression level was at 10 days post-flowering. The DlSERK1 expression level was down-regulated under low-temperature stress and up-regulated under drought and salt stresses. Our study showed that DlSERK1 was expressed in embryo development and could respond to low-temperature, drought, and salt stresses, which lays a foundation for further research on the function of SERK1 in the apomixis growth and development of environmental adaptation in D. lotus.