Identification of a Novel Regulator of Brassica napus Seed Development By Associative Transcriptomics

Identifying and using genetic variation that contributes to crop yield is a key aim in the breeding of major food and industrial crops such as oilseed rape (OSR). Using Associative Transcriptomics we screened a panel of OSR accessions for genetic variation associated with a range of yield component traits. This analysis identified a locus associated with the weight of seed per pod. The expression of a gene at this locus, encoding a ubiquitin ligase, correlated negatively with the observe trait variation. Concordant with this result, we show that Arabidopsis mutants lacking a functional copy of this gene produce significantly larger seeds relative to WT plants. This increase in seed size was coupled with a 12% increase in seed storage protein and a 13% increase in seed lipid levels. Assessment of gene expression throughout seed development revealed that a set of regulatory transcription factor genes known for their role in seed maturation are upregulated in mutant seeds relative to WT. Using a cell-free system we showed that the ubiquitin ligase mediates the proteosomal degradation of a master regulator of seed maturation. Closer inspection of the promoter region of the Brassica napus orthologue of this ubiquitin ligase revealed extensive variation which may be causal for the differential expression and consequent phenotypic variation observed. Such variation could be utilised in breeding programs for the direct selection of genotypes exhibiting large seed size with high lipid content.