Two dwarfing genes Rht-B1b and Rht-D1b show pleiotropic effects on grain protein content in bread wheat (Triticum aestivum L.).

KEY MESSAGE: Five QTL for wheat grain protein content were identified, and the effects of two dwarfing genes Rht-B1b and Rht-D1b on grain protein content were validated in multiple populations. Grain protein content (GPC) plays an important role in wheat quality. Here, a recombinant inbred line (RIL) population derived from a cross between Yangmai 12 (YM12) and Yanzhan 1 (YZ1) was used to identify quantitative trait loci (QTL) for GPC. Two hundred and five RILs and their parents were grown in three years in randomized complete blocks each with two replications, and genotyped using the wheat 55 K SNP array. Five QTL were identified for GPC on chromosomes 1A, 1B, 2D, 4B, and 4D. Notably, QGpc.yaas-4B (co-located with Rht-B1) and QGpc.yaas-4D (co-located with Rht-D1) were consistently detected across all experiments and best linear unbiased estimating, accounting for 6.61-8.39% and 6.05-10.21% of the phenotypic variances, respectively. The effects of these two dwarfing alleles Rht-B1b and Rht-D1b on reducing GPC and plant height were validated in two additional RIL populations and one natural population. This study lays a foundation for further investigating the effects of dwarfing genes Rht-B1b and Rht-D1b on wheat GPC.

Epigenomic identification of vernalization cis-regulatory elements in winter wheat.

BACKGROUND: Winter wheat undergoes vernalization, a process activated by prolonged exposure to low temperatures. During this phase, flowering signals are generated and transported to the apical meristems, stimulating the transition to the inflorescence meristem while inhibiting tiller bud elongation. Although some vernalization genes have been identified, the key cis-regulatory elements and precise mechanisms governing this process in wheat remain largely unknown. RESULTS: In this study, we construct extensive epigenomic and transcriptomic profiling across multiple tissues-leaf, axillary bud, and shoot apex-during the vernalization of winter wheat. Epigenetic modifications play a crucial role in eliciting tissue-specific responses and sub-genome-divergent expressions during vernalization. Notably, we observe that H3K27me3 primarily regulates vernalization-induced genes and has limited influence on vernalization-repressed genes. The integration of these datasets enables the identification of 10,600 putative vernalization-related regulatory elements including distal accessible chromatin regions (ACRs) situated 30Kb upstream of VRN3, contributing to the construction of a comprehensive regulatory network. Furthermore, we discover that TaSPL7/15, integral components of the aging-related flowering pathway, interact with the VRN1 promoter and VRN3 distal regulatory elements. These interactions finely regulate their expressions, consequently impacting the vernalization process and flowering. CONCLUSIONS: Our study offers critical insights into wheat vernalization's epigenomic dynamics and identifies the putative regulatory elements crucial for developing wheat germplasm with varied vernalization characteristics. It also establishes a vernalization-related transcriptional network, and uncovers that TaSPL7/15 from the aging pathway participates in vernalization by directly binding to the VRN1 promoter and VRN3 distal regulatory elements.