Research Projects

Plants being sessile organisms, have acquired various stress adaptations to survive the changing environments of their habitat. Mangroves inhabit extremely stressful intertidal regions of the world which possess diverse adaptive strategies to withstand the external stressors. Melatonin (N-acetyl-5-methoxytryptamine), an indolic compound derived from tryptophan and a well recognized animal hormone, has been identified as a regulator of plant abiotic stress responses. Melatonin effectively scavenges reactive oxygen/nitrogen species (ROS and RNS) and acts as a multi functional signaling molecule. Though the role of melatonin in abiotic stress tolerance is well recognized in other plants, the melatonin dynamics in antioxidative defense is yet to be studied in mangroves which possess several unique mechanisms to fight off abiotic stresses. Generally, melatonin is present in almost all plant tissues and its biosynthesis is typically restricted to mitochondria and chloroplasts. The biosynthetic pathway of melatonin in plants involve six major enzymes such as caffeic acid O-methyltransferase (COMT), N-acetylserotonin-O-methyltransferase (ASMR), serotonin N-acetyltransferase (SNAT), tryptamine 5-hydroxylase (T5H), tryptophan hydroxylase (TPH) and tryptophan decarboxylase (TDC). Among them, COMT is a multifunctional enzyme which also takes part in lignin biosynthesis. The regulation of lignin biosynthesis and the subsequent lignification of the cell walls also have a significant role in abiotic stress tolerance. The stress induced variations in lignification has recently been identified in mangroves (Recent study from our lab; Nizam et al., 2023a ), but how the regulation of COMT in melatonin biosynthesis/lignification is determined has not been addressed in mangrove abiotic stress tolerance. In this background, we propose to elucidate the interrelationships between melatonin and lignification of mangroves under salinity stress, the major abiotic stress factor mangroves experience. The variations in cellular biosynthesis of melatonin and the degree of lignification under exogenous application of melatonin will also be analyzed. Finally, the efficiency of mangrove specific COMT gene in crop improvement via enhancing melatonin dynamics and altering lignification will be tested in a model plant system with exact documentation of expression variations with and without exogenous application of melatonin.