Overexpression of tae-miR9670 enhances cadmium tolerance in wheat by targeting mTERFs without yield penalty

Abstract

Cadmium (Cd) is a widely distributed heavy metal that poses significant hazards to both crop productivity and human health. MicroRNAs (miRNAs) play pivotal roles in plant growth, development and responses to environmental stresses, yet little is known about their roles in regulating Cd tolerance in wheat. In this study, we identified tae-miR9670, a Triticeae-specific miRNA, as responsive to Cd exposure in wheat through miRNAome analysis. Tae-miR9670 can target genes that encode mitochondrial transcription termination factors (mTERFs), mediating their mRNA cleavage and suppressing their expression. Overexpression of tae-miR9670 significantly enhanced Cd tolerance in wheat seedlings, as demonstrated by increased biomass and reduced levels of malondialdehyde (MDA), H2O2, and Cd content. Consequently, multiple downstream genes involved in ROS scavenging, detoxification and heavy metal transport were upregulated in tae-miR9670 overexpression plants. Moreover, the grain Cd content in mature plants overexpressing tae-miR9670 was reduced by over 60 % compared to wild-type controls. Our results also indicated that overexpressing tae-miR9670 in wheat preserved yield-related traits, thereby overcoming the trade-off between stress resistance and grain yield. Overall, our findings provide new insights into the role of tae-miR9670 in Cd tolerance in wheat and its potential application in breeding low-Cd cultivars.