Genome Identification of GLP Family in Korean Pine and Study on the Function of GLP1-2-6/GLP1-2-21 in Somatic Embryo Maturation

Based on prior transcriptome data, we established a core gene interaction network for Korean pine somatic embryo maturation and screened 18 core genes. These genes showed distinct differential expression in early somatic embryogenesis. In particular, <i>PkGLP1-2-6 (Pkor04G01180)</i> and <i>PkGLP-1-2-21 (Pkor04G01200)</i> were highly correlated in the network and can be regarded as key genes mediating Korean pine somatic embryo maturation. A total of 92 members of the <i>PkGLP</i> gene family were identified in the Korean pine genome, which can be classified into 8 subfamilies based on evolutionary relationships. Both <i>PkGLP1-2-6</i> and <i>PkGLP1-2-21</i> were localized in the cell membrane and nucleus. By means of a stable genetic transformation system, transgenic Korean pine calli overexpressing <i>PkGLP1-2-6</i> and <i>PkGLP1-2-21</i> were successfully established. The results demonstrated that the overexpression of <i>PkGLP1-2-6</i> and <i>PkGLP1-2-21</i> could effectively promote somatic embryogenesis and enhance the yield of somatic embryos. In the presence of exogenous abscisic acid (ABA), the somatic embryo yield of the transgenic lines was significantly higher than that of the wild-type controls. Compared with the wild-type controls, the SOD activity in the cell lines overexpressing <i>PkGLP1-2-6</i> and <i>PkGLP1-2-21</i> was significantly increased, whereas the activities of POD and CAT were decreased, and the contents of H₂O₂ and superoxide anion (O₂^-) were significantly reduced. These results indicate that <i>PkGLP1-2-6</i> and <i>PkGLP1-2-21</i> are actively involved in the reactive oxygen species (ROS) scavenging process during somatic embryogenesis of Korean pine. The overexpression of <i>PkGLP1-2-6</i> and <i>PkGLP1-2-21</i> contributes to enhancing the antioxidant capacity of cells, thereby increasing the yield of somatic embryos.