UV-B priming of Oryza sativa var. Kanchana seedlings augments its antioxidative potential and gene expression of stress-response proteins under various abiotic stresses.

Priming is one of the mechanisms for the induction of the antioxidant defense system and various stress-responsive proteins which help plants to survive under various abiotic stresses. Based on the observation that the rice seedlings primed with UV-B (low dose of UV-B irradiation-6 kJm^-2) induced the acclimation against NaCl, PEG and UV-B stresses, it was of interest to see the augmentation of antioxidative potential and stress-responsive proteins accumulation in rice seedlings due to UV-B priming under these stresses. Various stresses result in production of ROS, which cause membrane degradation resulting in the accumulation of malondialdehyde. These negative impacts were observed exceedingly in rice seedlings from non-primed PEG stress (NP+P) condition than UV-B and NaCl stresses. The production of non-enzymatic antioxidants, activity/mRNA-level expressions of enzymatic antioxidants and stress-responsive proteins were effectively augmented in UV-B-primed rice seedlings subjected to NaCl stress (P+N) condition followed by UV-B stress (P+U) and PEG stress (P+P). The activation of stress-responsive proteins (HSP and LEA) in rice due to the UV-B priming of rice seedlings is being reported for the first time. The results revealed that the UV-B seedling priming was alleviating the effect of NaCl, PEG, and UV-B stresses in rice seedlings. The positive impacts of UV-B seedling priming were more prominent in rice seedlings subjected to NaCl stress, indicating the cross tolerance imparted by UV-B priming.