Auxin-salicylic acid cross-talk ameliorates OsMYB-R1 mediated defense towards heavy metal, drought and fungal stress.

The MYB TF family is an immensely large and functionally diverse class of proteins involved in the regulation of cell cycle, cell morphogenesis to stress signaling mechanism. The present study deciphered the hormonal cross-talk of wound inducible and stress-responsive OsMYB-R1 transcription factor in combating abiotic [Cr(VI) and drought/PEG] as well as biotic (Rhizoctonia solani) stress. OsMYB-R1 over-expressing rice transgenics exhibit a significant increase in lateral roots, which may be associated with increased tolerance under Cr(VI) and drought exposure. In contrast, its loss-of-function reduces stress tolerance. Higher auxin accumulation in the OsMYB-R1 over-expressed lines further strengthens the protective role of lateral roots under stress conditions. RNA-seq. data reveals over-representation of salicylic acid signaling molecule calcium-dependent protein kinases, which probably activate the stress-responsive downstream genes (Peroxidases, Glutathione S-transferases, Osmotins, Heat Shock Proteins, Pathogenesis Related-Proteins). Enzymatic studies further confirm OsMYB-R1 mediated robust antioxidant system as catalase, guaiacol peroxidase and superoxide dismutase activities were found to be increased in the over-expressed lines. Our results suggest that OsMYB-R1 is part of a complex network of transcription factors controlling the cross-talk of auxin and salicylic acid signaling and other genes in response to multiple stresses by modifying molecular signaling, internal cellular homeostasis and root morphology.