Amelioration of cadmium toxicity in Vicia faba via modulation of caffeic acid O-methyltransferase gene expression by biochar and nanobiochar

Abstract

Cadmium (Cd) is considered one of the most mobile and toxic environmental contaminant on all organisms. This study aimed to remove the toxicity effect of Cd with important natural materials without harmful side effect on the living organisms. Two concentrations (1% and 2%) of biochar and nano-biochar (with an average particle size of 15.13 nm) were applied to Vicia faba L. under Cd stress (200 µM) by adding them to Hoagland’s nutrition solution. Results indicated that Cd significantly decreased plant growth parameters (root and shoot length, fresh and dry weights of shoot and root and leaf area) and chlorophyll levels under Cd stress. Cd elevated the antioxidant enzymes and proline levels. The genes that are engaged in the melatonin pathway (N-acetylserotonin, methyltransferase, Serotonin N-acetyltransferase slightly interacted (if any) with Cd stress. Caffeic acid O-methyltransferase (COMT) only showed a significant response to Cd, with a 3.74-fold increase in expression at the first time-point. At the same time, biochar and nano-biochar effectively reduced the harmful effects of Cd on plant growth, improved physiological responses, and modulated the expression of the COMT gene. Nano-biochar exhibited particularly strong improvements across various growth parameters. This is the first time studying these genes in Vicia faba plants under any stress. COMT is involved in other pathways such as lignin pathway and might be expressed in response to Cd stress as a part of this pathway.