Overexpression of theTectona grandis TgNAC01regulates growth, leaf senescence and confer salt stress tolerance in transgenic tobacco plants

NAC transcription factors play critical roles in xylem secondary development and in regulation of stress response in plants. NAC proteins related to secondary cell wall development were recently identified and characterized inTectona grandis(teak), one of the hardwood trees of highest economic importance in the world. In this work, we characterized the novelTgNAC01gene, which is involved in signaling pathways that mediate teak response to stress. Abscisic acid (ABA) increasesTgNAC01expression in teak plants. Therefore, this gene may have a role in signaling events that mediate ABA-dependent osmotic stress responsive in this plant species. Stable expression in tobacco plants showed that the TgNAC01 protein is localized in the cell nucleus. Overexpression ofTgNAC01in two out three independent transgenic tobacco lines resulted in increased growth, leaf senescence and salt tolerance compared to wild type (WT) plants. Moreover, the stress tolerance of transgenic plants was affected by levels ofTgNAC01gene expression. Water potential, gas exchange and chlorophyll fluorescence were used to determine salt stress tolerance. The 35S:TgNAC01-6 line under 300 mM NaCl stress responded with a significant increase in photosynthesis rate, stomatal conductance, transpiration and carboxylation efficiency, but lower water potential compared to WT plants. The data indicate that theTgNAC01transcription factor acts as a transcriptional activator of the ABA-mediated regulation and induces leaf senescence.