Innovative screening for mutants affected in seed oil/protein allocation identifies TRANSPARENT TESTA7 as a regulator of oil accumulation.

Brassicaceae species mainly accumulate oil and protein in their seeds, which are essential to human life as a source of food, but also as animal feed and resources for green chemistry. To date, Brassicaceae crops such as rapeseed have been selected mainly for their oil content. However, there is a growing interest in their seed protein content. A strong negative correlation between oil and protein content makes it difficult to increase both compounds simultaneously. In this study, an Arabidopsis thaliana homozygous EMS mutant library was screened for seed oil and protein content by near-infrared spectroscopy with the aim of identifying mutants with impaired oil/protein correlation. The mutant most affected in this correlation was found to be in the TRANSPARENT TESTA7 gene, which is involved in the flavonoid biosynthetic pathway. Analysis of different mutants in the flavonoid pathway revealed that the tt7 mutants were the only ones to show such a significant reduction in seed oil content, highlighting a phenotype never described before for the tt7 mutants and suggesting a specific role for TT7 in the interplay between the oil and flavonoid biosynthetic pathways. Untargeted metabolomic analysis allowed the identification of metabolic features that are highly accumulated and specific to tt7 seeds compared to the other genotypes and genetic analysis established that the accumulation of kaempferol-3-O-rhamnoside seems to be responsible for the seed oil reduction in tt7 mutants.