ZmbHLH124 identified in maize recombinant inbred lines contributes to drought tolerance in crops

Due to climate change, drought has become a severe abiotic stress that affects the global production of all crops. Elucidation of the complex physiological mechanisms underlying drought tolerance in crops will support the cultivation of new drought‐tolerant crop varieties. Here, two drought‐tolerant lines, RIL70 and RIL73, and two drought‐sensitive lines, RIL44 and RIL93, from recombinant inbred lines (RIL) generated from maize drought‐tolerant line PH4CV and drought‐sensitive line F9721, were selected for a comparative RNA‐seq study. Through transcriptome analyses, we found that gene expression differences existed between drought‐tolerant and ‐sensitive lines, but also differences between the drought‐tolerant lines, RIL70 and RIL73. ZmbHLH124 in RIL73, named as ZmbHLH124 (T‐ORG) which origins from PH4CV and encodes a bHLH type transcription factor, was specifically up‐regulated during drought stress. In addition, we identified a substitution in ZmbHLH124 that produced an early stop codon in sensitive lines (ZmbHLH124 (S‐ORG)). Overexpression of ZmbHLH124 (T‐ORG), but not ZmbHLH124 (S‐ORG), in maize and rice enhanced plant drought tolerance and up‐regulated the expression of drought‐responsive genes. Moreover, we found that ZmbHLH124(T‐ORG) could directly bind the cis‐acting elements in ZmDREB2A promoter to enhance its expression. Taken together, this work identified a valuable genetic locus and provided a new strategy for breeding drought‐tolerant crops.