MusaNAC29-like transcription factor improves stress tolerance through modulation of phytohormone content and expression of stress responsive genes

Understanding the molecular mechanisms governed by genes and cross-talks among stress signaling pathways is vital for generating a broad view on stress responses in plants. Here, we analysed the effects of MusaNAC29-like transcription factor of banana on stress responses and report the quantitative modulation of phytohormone and flavonoid content and analysed the growth parameters and yield trait in transgenic banana plants. Expression of MusaNAC29-like transcription factor was strongly altered in responses to stress conditions and application of signaling molecules. Under control conditions, PMusaNAC29-like-GUS is activated in cells bordering xylem vessel elements and is strongly triggered in other cells types after influence of salicylic acid and abscisic acid. Transgenic banana plants of cultivar Rasthali and Grand Naine overexpressing MusaNAC29-like transcription factor displayed superior tolerance towards drought and salinity stress. LC-MS analysis indicated elevated levels of jasmonic acid and salicylic acid while content of zeatin was significantly reduced in leaves of transgenic banana lines. Transgenic banana lines displayed increased levels of gallic acid, coumaric acid, naringenin, chlorogenic acid while levels of vanillic acid and piperine were significantly reduced. Expression of stress related genes coding for antioxidants, thiol peptidase proteins, cold-regulated proteins, late embryogenesis abundant proteins, ethylene-responsive transcription factors, bHLH proteins, jasmonate-zim-domain proteins and WRKY transcription factors were significantly induced in transgenic banana lines. Though MusaNAC29-like transcription factor improved stress tolerance, its overexpression resulted in retarded growth of transgenic lines resulting in reduced yield of banana fruits.