TaABI19 positively regulates grain development in wheat

Abstract

Starch is the most important component in the endosperm, and its synthesis is regulated by multiple transcription factors (TFs) in cereals. However, whether the functions of these TFs are conserved among cereals remains unclear. In this study, we cloned a B3 family TF in wheat, named TaABI19, based on its orthologous sequence in maize (Zea mays L.). Alignment of the DNA and protein sequences showed that ABI19 is conserved in maize and wheat (Triticum aestivum L.). We found that TaABI19 is highly expressed in young spikes and developing grains, and encodes a nucleus-localized transcriptional activator in wheat. The taabi19-b1 null mutants obtained by EMS exhibited a down-regulation of starch synthesis, shorter grain length and lower thousand-grain weight (TGW). Furthermore, we proved that TaABI19 could bind to the promoters of TaPBF homologous genes and enhance their expression. Haplotype association showed that TaABI19-B1 is significantly associated with TGW. We found that Hap2 and Hap3 were favored and had undergone positive selection in China’s wheat breeding programs. Less than 50% of the modern cultivars convey the favored haplotypes, indicating that TaABI19 still can be considered as a target locus for marker-assisted selection breeding to increase TGW in China.