Microbe-Mediated Mitigation of Cadmium Toxicity in Plants

There has been increasing evidence of cadmium (Cd) toxicity and accumulation in various plant parts. Due to its mobile nature, Cd becomes an integral part of the food chain, causing a threat to humans in terms of kidney, liver, and lung diseases. In Cd-prone areas, leaf chlorosis, stunted growth, and inhibition of photosynthesis are the symptoms displayed by many plants. Microbe-mediated induction of Cd-stress tolerance is associated with various plant-based mechanisms, including alteration of phytohormone levels, modulation of the expression of defense-related proteins, upregulation of antioxidant enzymes, and expression modulation of metal transporters; and microbe-based mechanisms, including growth hormone production, better nutrient assimilation, siderophore production, 1-amino cyclopropane-1-carboxylate (ACC) deaminase activity, exopolysaccharide production, and so forth. Moreover, the rhizosphere microbes, especially bacteria and fungi, alter the state of toxic metal compounds and trigger the process of phytoremediation. Nevertheless, scientists need to explore new mechanisms and microbial signals for Cd-stress alleviation, coupled with increased plant productivity.