CRISPR/Cas9 editing of wheat TaQ genes alters spike morphogenesis and grain threshability

The TaQ alleles as one of the AP2-like transcription factors in common wheat (Triticum aestivum) play an important role in the evolution of spike characteristics from wild and domesticated emmer to modern wheat cultivars. Its loss-of-function mutant not only changed threshability and spike architecture but also affected plant height, flowering time, and floret structure. However, the comprehensive functions of TaAQ and TaDq genes in wheat have not been fully elucidated yet. Here, CRISPR/SpCas9 was used to edit wheat TaAQ and TaDq. We obtained homozygous plants in the T₁ generation with loss of function of only TaAQ or TaDq and simultaneous loss of function of TaAQ and TaDq to analyze the effect of these genes on wheat spikes and floret shapes. The results demonstrated that the TaAQ-edited plants and the TaAQ and TaDq simultaneously-edited plants were nearly similar in spike architecture, whereas the TaDq-edited plants were different from the wild-type ones only in plant height. Moreover, the TaAQ-edited plants or the TaAQ and TaDq simultaneously-edited plants were more brittle than the wild-type and the TaDq-edited plants. Based on the expression profiling, we postulated that the VRN1, FUL2, SEP2, SEP5, and SEP6 genes might affect the number of spikelets and florets per spike in wheat by regulating the expression of TaQ. Combining the results of this report and previous reports, we conceived a regulatory network of wheat traits, including plant height, spike shape, and floral organs, which were influenced by AP2-like family genes. The results achieved in this study will help us to understand the regulating mechanisms of TaAQ and TaDq alleles on wheat floral organs and inflorescence development.