Nitric oxide in plants: an ancient molecule with new tasks

Multitasking capability of nitric oxide (NO) makes it a highly investigating signaling molecule in plant biology. In plants including inflection of hormonal levels, fruit ripening, wound suppression and defensive responses, and regulation of programmed cell death, much progress in NO signaling cascades has been achieved. Additionally, growing evidences suggest the interactive behavior of NO with auxin, salicylic acid, abscisic acid, jasmonic acid and thus regulates their signaling pathways. Parallel to this, reactive oxygen species (ROS) along with NO are supposed to accomplish various developmental and stress responses. Under biotic stress, signaling initiated by NO was found to be mediated by two specific protein i.e. pathogenesis-related 1 (PR-1) and phenylalanine ammonia lyase. The above mentioned genes were also promoted by second messengers like cyclic GMP (cGMP) and cyclic ADP-ribose (cADPR), which further initiate and regulate NO signaling. In plants, important mechanism is programmed cell death regulating various growth and developmental aspects by acting as a damage control. Under stress condition the infected cells are removed by involving signaling agents i.e. NO and ROS which is a matter of crosstalk in recent years. Keeping above facts into consideration, present work mainly deals with NO signaling under adverse conditions as well as its interaction with different phytohormones and ROS.