TaSED interacts with TaSPA synergistically regulating SDS-sedimentation volume in bread wheat

The SDS-sedimentation volume (SSV) is a critical indicator for assessing wheat gluten quality and is widely used when evaluating wheat processing quality. However, the molecular mechanisms regulating SSV remain poorly understood. In this study, we performed an analysis of quantitative trait loci (QTLs) for SSV using a recombinant inbred line (RIL) population derived from a cross between TAA10 and XX329, and identified four environmentally stable QTLs located on chromosomes 1D, 2D, 4D, and 6D. Among them, the effects of Qssv.cau-1D and Qssv.cau-6D were likely to be explained by genome variations at the Glu-D1 and Gli-D2 loci. We fine mapped Qssv.cau-2D to the candidate causal gene TaSED, encoding a nucleolar protein. Gene-edited TaSED knockout mutants (tased) had a lower SSV, while TaSED overexpression lines showed a higher SSV. We demonstrated that TaSED interacted with the transcription factor TaSPA to enhance its transcriptional activation activity of glutenin and gliadin, whose expression was downregulated in tased and upregulated in TaSED-OE plants, with corresponding differences in glutenin and gliadin content compared with the wild-type. A molecular marker sedTX was further developed based on a nonsynonymous mutation of the parents in TaSED that could be used to identify haplotypes with high SSV effectively. Our findings elucidate a molecular mechanism governing SSV and reveal valuable variants with promising applications for improving wheat quality.