Cloning of PkSERKs genes in Korean pine and analysis of their expression in different callus types

This study cloned the PkSERK genes from Korean pine (Pinus koraiensis) and analyzed their expression characteristics, laying a foundation for functional research on PkSERKs in somatic embryogenesis of Korean pine.

The full-length coding sequence (CDS) of PkSERK1-3 gene in Korean pine was successfully cloned, subsequent bioinformatics analyses were conducted to examine the protein structure, physicochemical properties, and evolutionary relationships, subcellular localization was observed with green fluorescent protein (GFP) technology, additionally, and the expression patterns of these three genes in seven types of korean pine calli were analyzed by qRT-PCR technology.

PkSERK1, PkSERK2, and PkSERK3 were successfully cloned, with cDNA lengths of 1 824, 1 887 and 1 437 bp, encoding 607, 628 and 448 amino acids, respectively. PkSERK1 is an acidic, hydrophilic, and stable protein, while PkSERK2 is an acidic, hydrophilic, and unstable protein, and PkSERK3 is a basic, hydrophilic, and unstable protein; both PkSERK1 and PkSERK2 contain a signal peptide, whereas PkSERK3 does not have a signal peptide; these three proteins are all transmembrane proteins. The PkERK1 protein has the closest genetic relationship with ClSERK1-3 of Cunninghamia lanceolata, PkSERK2 has the closest genetic relationship with CsSERK1 of Camellia sinensis, and PkSERK3 has the closest genetic relationship with CjSERK3 of Cryptomeria japonica. PkSERK1 and PkSERK2 were located in the cell membrane, while PkSERK3 was located in the cell membrane and nucleus. The PkSERK1 gene was highly expressed in both callus with high embryogenic potential and callus with globular embryos of korean pine; PkSERK2 was highly expressed in brown callus; PkSERK3 was only highly expressed in callus with high embryogenic potential.

The genes of PkSERK1, PkSERK2 and PkSERK3 were cloned from korean pine, PkSERK1 may regulate the maintenance of embryogenic potential in callus and early globular embryo differentiation in Korean pine, high expression of PkSERK2 may be associated with browning embryogenic callus (EC) and early globular embryo differentiation in Korean pine, while PkSERK3 may only play a role in the maintenance of embryogenic potential in Korean pine callus.