Is a Quantitative Trait Locus That Controls Seed Size.

Seed size is a key trait affecting evolution and agronomic performance by influencing seedling establishment in natural populations and crop yields. The Seed Size QTL1 (SSQ1) locus explains 10-15% of the variation in seed size. We report here that the causal gene for this locus is (), which encodes a co-chaperone. Expressing across ecotypes and genotypes showed consistent dosage effects. Each additional allele increased seed mass and volume by 10-14% with high reliability in Col-0, Sha, Tsu-1, and genetic backgrounds. Reciprocal genetic crosses indicated that this locus acts maternally, consistent with female sporophytic or female gametophytic mutations. To elucidate how regulates seed size, the biomass composition of seeds was measured. While oil content remained unchanged, sucrose levels were markedly elevated in transformant lines and reduced in mutants. Interestingly, heterologous expression of across genetic backgrounds increased seed protein accumulation by 18% on average. Based on these changes in sucrose and protein levels, potential modes of action for are discussed.