REACTIVE OXYGEN AND NITROGEN SPECIES: KEY PLAYERS IN PLANT RESPONSE TO STRESS

Under different biotic and abiotic stresses, plants exhibit rapid synthesis of nitric oxide (NO) and a parallel accumulation of reactive oxygen species (ROS). At low concentrations, ROS and RNS act as signals for regulation of plant growth and development and also for defense against stress. Moreover, they have great potential to exhibit defensive roles against various biotic and abiotic stresses. ROS comprises of hydrogen peroxide, hydroxyl radical, singlet oxygen molecule and superoxide anions. RNS peroxynitrite is produced upon the reaction between nitric oxide and superoxide anion and it has been reported as an effective regulator of cell signaling in plants by process of tyrosine nitration. Signaling mediated by ROS and RNS is chiefly related with plant hormones which affect acclimation, pathophysiology and normal ontogeny of plants. In the context of drought stress, it has been demonstrated that stress-responsive transcription factors play an important role in ROS and RNS metabolism. The present review highlights the current understanding and crosstalk between ROS and RNS in plant stress responses.