Identification of the ABHD6 gene family and development of functional markers for grain weight in wheat

α/β-Hydrolase domain-containing protein 6 (ABHD6), a key member of the serine hydrolase superfamily, plays important roles in regulating plant growth, development, and responses to environmental stress. However, a systematic genome-wide identification and analysis of the ABHD6 gene family in wheat (Triticum aestivum L.) is still lacking. Here, we integrated phylogenetic analysis, protein sequence characterization, promoter cis-acting element prediction, and haplotype analysis, and identified 18 TaABHD6 family members in the wheat genome. Phylogenetic and structural analyses showed that TaABHD6 proteins are closely related to rice OsABHD6 proteins, and that members within the same clade share highly conserved domains. Promoter analysis revealed that TaABHD6 promoters are enriched in cis-acting elements associated with plant growth and development. By analyzing polymorphisms in TaABHD6 genes and their associations with grain phenotypes, we identified eight genes with distinct haplotypes. Haplotype variation in three genes was significantly associated with grain-related traits; in particular, TaABHD6-5 haplotypes were significantly associated with grain weight, length, width, and thickness. We developed a KASP marker based on an A/T SNP at -1045 bp in the TaABHD6-5 promoter. Validation in 305 wheat accessions showed that this functional marker effectively distinguished two haplotypes: 268 accessions carried TaABHD6-5-HapI, 34 carried TaABHD6-5-HapII, two were heterozygous, and one accession failed genotyping. Association analysis further indicated that TaABHD6-5-HapI is a favorable haplotype for increased grain weight. qRT-PCR showed that TaABHD6-5 was relatively highly expressed in stems and spikes at booting and during early grain development; notably, expression was significantly lower in the favorable haplotype TaABHD6-5-HapI than in TaABHD6-5-HapII, suggesting that TaABHD6-5 may act as a negative regulator of grain weight. Sequence analysis further suggested that TaABHD6-5 is targeted by miR160. Together, these results provide genome-wide evidence for the roles of TaABHD6 genes in wheat grain development and highlight the potential breeding value of superior haplotypes.