Non-additive dosage-dependent effects of TaGS3 gene editing on grain size and weight in wheat

The grain size in cereals is one of the main component traits contributing to yield. Previous studies showed that loss-of-function (LOF) mutations in GS3, encoding Gγ subunit of the multimeric G protein complex, increase grain size and weight in rice. While association between allelic variation in GS3 homologs of wheat and grain weight/size was detected previusly, the effects of LOF alleles on these traits remain unknown. We used genome editing to create the TaGS3 mutant lines with the LOF homeo-allele dosage variation. Contrary to results obtained for rice, editing of all three TaGS3 copies result in significant decrease in grain length, width, grain area and weight, without affecting number of grains per spike. Compared to wild type, the highest increase in grain weight and area was observed in mutants with the intermediate dosage of the LOF alleles, indicating that suppressive effects of TaGS3 on grain size and weight in wheat are dosage-dependent and non-additive. Our results suggest that TaGS3 likely represents a functionally diverged homolog of GS3 evolved in the wheat lineage. The newly developed LOF alleles of TaGS3 expand the set of CRISPR-Cas9-induced variants of yield component genes that could be used for increasing grain weight in wheat.