Q allele overexpression and alternative splicing can improve wheat yield by increasing thousand-kernel weight and grain number per spike

BACKGROUND: Thousand-kernel weight and grain number per spike are key determinants of grain yield. Q is one of the most important domestication genes in wheat. A missense mutation (C3129T) at the microRNA172-binding site of Q (Qc1 allele) significantly increases the thousand-kernel weight, but also results in extremely compact spikes, leading to decreases in grain number per spike and yield, which is unfavorable for breeding and wheat production. RESULTS: We characterized a new Q allele (Qc1-Q1) obtained by treating the Q gene mutant line S-Cp1-1 (carrying Qc1) with ethyl methanesulfonate. A comparison with the domesticated Q allele widely distributed in modern common wheat cultivars revealed that Qc1-Q1 contains two missense mutations: C3129T (as in Qc1) and G542A in the splice site of the second intron. G542A results in alternative splicing, leading to the production of two protein forms. Moreover, it reverses the extremely compact spike phenotype due to C3129T. Field experiments indicated that Qc1-Q1 can increase wheat yield by simultaneously increasing the thousand-kernel weight and grain number per spike. Notably, the positive effect of Qc1-Q1 on yield did not negatively affect grain quality. Furthermore, we developed a specific marker on the basis of G542A to accelerate the application of Qc1-Q1 in wheat breeding programs. CONCLUSION: In this study, we developed a new approach to generating favorable Q alleles, while also producing germplasm potentially useful for breeding new wheat varieties with optimal grain production.