Comprehensive analysis of bHLH genes in wheat and functional characterization of TabHLH319 in salt tolerance

We identified 479 putative TabHLH genes in Zhou8425B and systematically analyzed their functions. TabHLH319 was revealed as a key salt tolerance gene significantly associated with yield-related traits. The basic helix-loop-helix (bHLH) transcription factors represent one of the largest gene families in plants, playing vital roles in development and stress responses. Here, we bioinformatically identified 479 bHLH genes in the high-quality genome of the wheat core parent Zhou8425B and classified them into 13 subfamilies. We investigated their gene structures and computed their physicochemical properties and phylogenetic relationships. RNA-seq data from 12 tissues revealed diverse and tissue-specific expression patterns, several bHLH genes were identified as responsive to various environmental stresses, among which TabHLH319 was implicated in salt tolerance. Sequence comparison between Zhou8425B and Chinese Spring (CS) revealed a nonsynonymous SNP in the exon of TabHLH319. Moreover, a 57-bp insertion in the promoter region specific to Zhou8425B. A molecular marker targeting the InDel was developed and used to genotype a recombinant inbred line (RIL) population derived from Zhou8425B × CS. Dual-luciferase assays demonstrated that this 57-bp insertion significantly enhanced promoter activity under salt stress, explaining the elevated expression of TabHLH319^Zhou8425B observed by RT-qPCR in leaf, root, and stem tissues. Under salt stress, RILs carrying the TabHLH319^Zhou8425B exhibited greater salt tolerance, accompanied by higher POD, SOD, and CAT enzyme activities, increased proline content, and lower H₂O₂ and MDA levels. Further analysis showed that TabHLH319^Zhou8425B was significantly associated with enhanced yield-related traits, such as thousand kernel weight, kernel length, and kernel width. This study comprehensively characterizes the bHLH genes in Zhou8425B and highlights TabHLH319 as a key gebidopsis bHLH family. Grouping data ne for salt tolerance and wheat molecular breeding.