TaMYC8 regulates TaERF6 and inhibits ethylene synthesis to confer Cd tolerance in wheat

Cadmium (Cd) is a toxic, nonessential heavy metal; its accumulation in plants alters metabolism and limits productivity. Although various studies have addressed the Cd stress response in various species, the detailed molecular mechanisms remain unknown. Therefore, the present work investigated the influence of the TaMYC8 transcription factor (TF) on the Cd-induced stress response in wheat. The present study found that TaMYC8 is a nuclear protein highly induced in the roots under Cd stress. Overexpression of TaMYC8 in the wheat cultivar 'Bobwhite' increased sensitivity to Cd stress, probably due to the increased levels of superoxide (O2.-), malonaldehyde (MDA), jasmonic acid (JA), and Cd, and reduced the proline content and antioxidant enzyme activity. In contrast, silencing TaMYC8 via RNA interference (RNAi) significantly lowered Cd accumulation and improved Cd tolerance. Using the yeast one-hybrid assay (Y1H), chromatin immunoprecipitation-quantitative polymerase chain reaction (ChIP–qPCR), electrophoretic mobility shift assay (EMSA), and dual luciferase reporter assay, it was found that TaMYC8 could physically bind to the TaERF6 promoter and activate TaERF6 transcription. More importantly, knockdown of TaMYC8 by RNAi inhibited the activities of 1-aminocyclopropane-1-carboxylic (ACC) acid synthase (ACS) and ACC oxidase (ACO) of the ethylene biosynthetic pathway. In conclusion, TaMYC8 promotes TaERF6 transcription and affects the ethylene biosynthetic pathway. These findings provide a theoretical basis for breeding low-Cd-accumulating wheat cultivars.