Overexpression of a Malus baccata WRKY transcription factor gene (MbWRKY5) increases drought and salt tolerance in transgenic tobacco

WRKY transcription factors are widely involved in abiotic stress responses in plants. However, their roles in abiotic stresses of Malus plants are still not well known. In this study, a WRKY gene is isolated from Malus baccata (L.) Borkh and designated as MbWRKY5. MbWRKY5 contains two WRKY domains and one Cys2-His2 (C2H2) zinc-finger motif, and was localized in nucleus. The expression levels of MbWRKY5 were up-regulated by salinity, heat, cold, drought and abscisic acid (ABA) treatments in M. baccata seedlings. When MbWRKY5 was introduced into tobacco, an improvement in tolerance to drought and salt was achieved in transgenic plants. Under drought and salt treatments, the transgenic plants had higher contents of chlorophyll, proline, glutathione (GSH) and Ascorbate (AsA), and increased activities of peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) than wild type (WT) tobaccos. Compared to WT plants, over-expression of MbWRKY5 in transgenic tobacco also led to decreased levels of malondialdehyde (MDA) and hydrogen peroxide (H2O2) under drought and salt stresses. Moreover, the MbWRKY5-OE tobaccos increased the expression levels of stress-related genes involved in oxidative stress response (NtPOD, NtSOD and NtCAT) and membrane protection (NtLEA5, NtERD10D and NtP5CS), especially under drought and salt stresses. These results suggest that MbWRKY5 gene plays a positive regulatory role in drought and salt stress responses.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author