TaABI19 positively regulates grain development in wheat

Starch is the most important component in endosperm, and its synthesis is regulated by multiple transcription factors (TFs) in cereals. However, whether the functions of these TFs are conserved or not among cereals unclear yet. Here, we cloned a B3 family TF, named as TaABI19 based on its orthologous in maize ( Zea mays L.). Alignment of DNA and protein showed that ABI19 was conserved in maize and wheat ( Triticum aestivum L.). We found that TaABI19 was highly expressed in young spike and developing grains and encoded a nucleus-localized transcriptional activator in wheat. The taabi19-b1 null mutants obtained by EMS performed down-regulation of starch synthesis, shorter grain length and lower thousand grain weight (TGW). Furthermore, we provided TaABI19 could bind to the promoters of TaPBF homology genes and enhance their expression. Haplotype association showed that TaABI19-B1 was significantly associated with TGW. We found that Hap2 and Hap3 were favored and underwent positive selection in China wheat breeding. Less than fifty percent in the modern cultivars conveying favored haplotypes indicates TaABI19 still can be considered as target loci for marker-assisted selection breeding to increase TGW in China.