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

Loss-of-function mutations induced by CRISPR-Cas9 in the TaGS3 gene homoeologs show non-additive dosage-dependent effects on grain size and weight and have potential utility for increasing grain yield in wheat. The grain size in cereals is one of the 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 an association between allelic variation in the GS3 homologs of wheat and grain weight/size has been detected previously, the effects of LOF alleles at TaGS3 on these traits remain unknown. We used genome editing to create TaGS3 mutant lines with varying LOF homeo-allele dosages. Contrary to the results obtained in rice, editing all three TaGS3 homoeologous copies resulted in a significant decrease in grain length (4.4%), width (3.4%), grain area (7.3%) and weight (7.5%), without affecting the number of grains per spike. Compared to the wild type, the highest increase in grain weight (up to 9.6%) and area (up to 5.0%) was observed in homozygous mutants with one or two genomes carrying LOF homeo-alleles, suggesting non-additive suppressive effects of TaGS3 on grain size and weight in wheat. Our results suggest that the regulatory effects of GS3 homologs in wheat and rice have diverged. The newly developed LOF homeo-alleles of TaGS3 expand the set of CRISPR-Cas9-induced variants of yield component genes that have potential to increase grain weight in wheat.