MYB transcription factors (TFs) represents one of the largest TF families in plants. In this study, we performed genome-wide MYB-domain screening and identified a total of 997 MYBs in wheat (Triticum aestivum), among which 445 were 2-domain MYBs (R2R3-MYBs) that were clustered into 15 subgroups with varied conservation profiles. Homologous genes were highly conserved across the three subgenomes, with minor variations contributed by segmental duplications. Tandem and proximal gene duplications have contributed significantly to the expansion of the wheat Myb gene family. Furthermore, comprehensive transcriptome profiling of R2R3-Myb genes in 61 different tissue and time point samples revealed a clear pattern of temporal and spatial variations within six expression groups. The comprehensive genomic and transcriptional analyses provided valuable insights into the evolution and biological functions of R2R3-Myb genes in wheat. They would serve as a useful guide to further investigate the potential agronomic traits controlled by this large TF family.

Pre-harvest sprouting (PHS) induced by the absence of seed dormancy causes a severe reduction in crop yield and flour quality. In this study, we isolated and characterized TaABI4, an ABA-responsive transcription factor that participates in regulating seed germination in wheat. Sequence analysis revealed that TaABI4 has three homologues, located on chromosomes 1A/1B/1D. TaABI4 contains a conserved AP2 domain, and AP2-associated, LRP and potential PEST motifs. Putative cis-acting regulatory elements (CE1-like box, W-box, ABRE elements and RY elements) were identified in the TaABI4 promoter region that showed high conservation in 17 wheat cultivars and wheat-related species. Expression profiling of TaABI4 indicated that it is a seed-specific gene accumulating during the middle stages of seed development. Transcript accumulation of TaABI4 in wheat cultivar Chuanmai 32 (CM32, PHS susceptible) was 5.07-fold and 1.39-fold higher than that in synthetic hexaploidy wheat SHW-L1 (PHS resistant) at 15 and 20 DPA, respectively. Six expression quantitative trait loci (eQTL) of TaABI4 on chromosomes 2A, 2D, 3B and 4A were characterized based on the accumulated transcripts of TaABI4 in SHW-L1 and CM32-derived recombinant inbred lines. These QTLs explained 10.7 to 46.1% of the trait variation with 4.53–10.59 of LOD scores, which contain genes that may affect the expression of TaABI4.

Pre-harvest sprouting (PHS) induced by the decline of seed dormancy causes a severe reduction in crop yield and flour quality. In this study, we isolated and characterized TaABI4, an ABA-responsive transcription factor that participates in regulating seed germination in wheat. Sequence analysis revealed that TaABI4 has three homologues, located on chromosomes 1A/1B/1D. TaABI4 contains a conserved AP2 domain, and AP2-associated, LRP, and potential PEST motifs. Putative cis-acting regulatory elements (CE1-like box, W-box, ABRE elements, and RY-elements) were identified in the TaABI4 promoter region that showed high conservation in 17 wheat cultivars and wheat-related species. Expression profiling of TaABI4 indicated that it is a seed-specific gene accumulating during the middle stages of seed development. Transcript accumulation of TaABI4 in wheat cultivar Chuanmai 32 (CM32, PHS susceptible) was 5.07-fold and 1.39-fold higher than that in synthetic hexaploidy wheat SHW-L1 (PHS resistant) at 15DPA and 20DPA, respectively. Six expression quantitative trait loci (eQTL) of TaABI4 on chromosome 2A, 2D, 3B, and 4A were characterized based on the accumulated transcripts of TaABI4 in SHW-L1 and CM32 derived recombinant inbred lines. These QTLs explained from 10.7% to 46.1% of the trait variation with 4.53~10.59 of LOD scores, which contain genes that may affect the expression of TaABI4.