Harnessing melatonin and plant growth promoting rhizobacteria (PGPRs) competency to mollify Cd toxicity in B. junea L

Microbes of phytomicrobiome are related to plant tissues and in association with plants form the holobiont. Beneficial microorganisms include those that establish synergistic associations with plant roots in order to shore up nutrient mineralization and availability. They aid plants by promoting their growth and in suppression of diseases. Heavy metal resistant plant growth promoting rhizobacteria (HMR-PGPR) are well known for resisting heavy metal toxicities and enhancing plant growth and yield. Melatonin (MEL) is a phytohormone that has a significant role in heavy metal remediation in various plants. It is a pleiotropic molecule with many diverse actions in plants. It is considered primarily an antioxidant with important actions in the control of reactive oxygen and nitrogen species (ROS and RNS), among other free radicals and harmful oxidative molecules present in plant cells. Since rhizobacteria and melatonin hormone have been reported to ameliorate various stresses, it was proposed to observe the combined effect of these to counter Cd toxicity in B. juncea L. Two strains were decided namely Pseudomonas putida (M1) and Pseudomonas florescence (M2) which were procured from MTCC, Chandigarh. It was observed in the present study that Cd stress (0.3mM) altered physiological and metabolic processes in Brassica juncea L. It was observed that supplementation with microorganisms in Cd exposed seedlings resulted in reducing toxicity levels by upregulating antioxidative defense responses and increasing the levels of different secondary metabolites such as phenolic compounds and osmolytes. The histological studies also provided insight into impact of ROS on cellular processes, thereby strengthening the proposed hypothesis. The study may play an important role in understanding the stress protective role of melatonin and rhizobacteria in plants under metal stress.

Audience Take Away:

• Till now an extensive amount of work has been done on classical Plant hormones, in our study the new hormone i.e. melatonin is considered to study its impact on B. juncea under cadmium stress.
• Along with melatonin an organic amendment is done by adding plant growth promoting rhizobacteria (Pseudomonas putida and Pseudomonas florescence).
• The impact of both plant growth regulator and plant growth promoting rhizobacteria will be understood.