Cloning and expression analysis of a homologous expansin gene EXP2 in Picea wilsonii

Expansins are cell-wall-loosening proteins that have multiple roles during plant development and stress-related processes. In this study, a novel expansin gene PwEXP2 was cloned by rapid amplification of cDNA ends based on the cDNA library of Picea wilsonii and EST fragment of PwEXP2. It was found that PwEXP2 coded 253 amino acids, and putative signal peptides exist at the N-terminal, followed by 8 cysteines, a HFD (His-Phe-Asp) conserved domain, and 4 tryptophan residues at the C-terminal. PwEXP2 was located in cytoplasm and nucleus when transformed in an onion epidermal cell. Quantitative real-time PCR assays showed that PwEXP2 was expressed in various tissues with a relatively high level in needles and low level in mature pollen. The expression level of PwEXP2 dramatically increased after seed germination. Gene expression profiles in abiotic stresses showed that PwEXP2 was induced by high temperature and osmotic stress but not involved in ABA-dependent signaling pathway. These results display the important roles of the PwEXP2 in plant development and multiple adversity stresses.