Genome-wide analysis of Q binding reveals a regulatory network that coordinates wheat grain yield and grain protein content

Wheat is an important cereal crop used to produce diverse and popular food worldwide because of its high grain yield (GY) and grain protein content (GPC). However, GY and GPC are usually negatively correlated. We previously reported that favorable alleles of the wheat domestication gene Q can synchronously increase GY and GPC, but the underlying mechanisms remain largely unknown. In this study, we investigated the regulatory network involving Q associated with GY and GPC in young grains through DNA affinity purification sequencing and transcriptome sequencing analyses, electrophoretic mobility shift and dual-luciferase assays, and transgenic approaches. Three Q-binding motifs, namely TTAAGG, AAACA[A/T]A, and GTAC[T/G]A, were identified. Notably, genes related to photosynthesis or carbon and nitrogen metabolism were enriched and regulated by Q. Moreover, Q was revealed to bind directly to its own gene and the glutamine synthetase gene GSr-4D to increase expression, thereby influencing nitrogen assimilation during the grain filling stage and increasing GPC. Considered together, our study findings provide molecular evidence of the positive regulatory effects of Q on wheat GY and GPC.