* Correspondence: Delong Yang, yangdl@gsau.edu.cn; Tao Chen, chent@gsau.edu.cn

Seven in absentia (SINA) proteins, which contain a conserved SINA domain, are involved in regulating various aspects of wheat growth and development, especially in response to environmental stresses. However, it is unclear whether TaSINA family members are involved in regulating grain development until now. In this study, the expression pattern, genomic polymorphism, and relationship with grain-related traits were analyzed for all TaSINA members.

Most of the TaSINA genes identified showed high expression levels in young wheat spikes or grains. The genomic polymorphism analysis revealed that at least 62 TaSINA genes had different haplotypes, and the haplotypes of five genes were significantly correlated with grain-related traits. Kompetitive allele-specific PCR (KASP) markers were developed to confirm the single nucleotide polymorphisms in TaSINA101 and TaSINA109 among the five selected genes in a set of 292 wheat accessions.

The TaSINA101-Hap II and TaSINA109-Hap II haplotypes had higher grain weight and width compared to TaSINA101-Hap I and TaSINA109-Hap I in at least three environments, respectively. The qRT-PCR assay revealed that TaSINA101 was highly expressed in the palea shell, seed coat, and embryo in young wheat grains.

The TaSINA101 protein was unevenly distributed in the nucleus when transiently expressed in the protoplast of wheat.

Three homozygous TaSINA101 transgenic lines in rice showed higher grain weight and size compared to the wild type. These findings provide valuable insight into the biological function and elite haplotype of TaSINA family genes in wheat grain development at a genomic-wide level.