Homologous HAP5 subunit from Picea wilsonii improved tolerance to salt and decreased sensitivity to ABA in transformed Arabidopsis.

HAP is a ubiquitous transcription factor family which consists of three distinct subunits, namely HAP2, HAP3, and HAP5. Among them, HAP2 and HAP3 subunits have been reported to be involved in plant response to abiotic stress. Here, a HAP5 subunit was identified from Picea wilsonii Mast. and transformed to Arabidopsis to investigate its functions in plant stress response. We found that transformed Arabidopsis with over-expressing PwHAP5 exhibited higher seed germination under salinity, osmotic and abscisic acid (ABA) stress treatment compared to Col-0 plants. The seedlings of transformed Arabidopsis also showed improved tolerance to salinity and decreased sensitivity to ABA treatment. Over-expression of PwHAP5 in Arabidopsis athap5 mutant rescued partly tolerance to NaCl, mannitol and ABA treatment. Furthermore, we examined transcription levels of several stress-related genes in transformed seedlings. Among them, mRNA expression levels of COR15a, KIN1, DREB2A, and RD29A genes were substantially higher in transformed Arabidopsis than those in wild-type (Col-0) plants. Therefore, our data revealed that PwHAP5 plays positive roles in response to salinity, osmotic and ABA stress at different developmental stages in plants, respectively, via possibly regulating stress-related genes.