Variation in expression of the HECT E3 ligase UPL3 modulates LEC2 levels, gene expression, seed size and crop yields in Brassica napus

Abstract

Identifying genetic variation that increases crop yields is a primary objective in plant breeding. We have used association analyses of Brassica napus (oilseed rape/canola) accessions to identify variation in the expression of a HECT E3 ligase gene, BnaUPL3.C03, that influences seed size and final yield. We establish a mechanism in which UPL3 mediates the proteasomal degradation of LEC2, a master regulator of seed maturation. Reduced UPL3 expression increases LEC2 protein levels and prolongs expression of lipid biosynthetic genes and seed maturation. Natural variation in BnaUPL3.C03 expression has not yet been exploited in current Brassica napus breeding lines and can therefore be used as a new approach to maximize future yields in this important oil crop.

Recent progress in molecular genetics and omics-driven research in seed biology

“…Finally, the ectopic expression of LEC1 or LEC2 in vegetative tissues can trigger the formation of somatic embryos, implying that these TFs are sufficient to confer embryonic cell identity. Consistent with the key functions of the LAFL genes in the induction and control of seed development, their expression is tightly controlled through numerous transcriptional and chromatin-based mechanisms as described in more details below (Figure 1), while the LAFL proteins are subjected to post-translational regulations [19,58,59].…”

“…Enfin, l'expression ectopique de LEC1 ou LEC2 dans les tissus végétatifs peut déclencher la formation d'embryons somatiques, ce qui implique que ces TF sont suffisants pour conférer une identité embryonnaire à des cellules. Conformément aux fonctions clés des gènes LAFL dans l'induction et le contrôle du développement de la graine, leur expression est étroitement contrôlée par de nombreux mécanismes transcriptionnels et chromatiniens, comme décrit plus en détail ci-dessous (Figure 1), tandis que les protéines LAFL sont soumises à des régulations post-traductionnelles [19,58,59]. 1).…”

Genetic mapping reveals a candidate gene CmoFL1 controlling fruit length in pumpkin

“…Silencing of TaSDIR1-4A (a RING-type E3 ubiquitin ligase) led to an increase in wheat TGW (1000-grain weight), while overexpression of TaSDIR1-4A in Arabidopsis resulted in a decrease in seed size (Wang et al, 2020a). In Brassica napus, variation in the promoter region of the HECT E3 ligase gene BnaUPL3.C03 made a major contribution to variation in seed weight per pod (Miller et al, 2019). In addition, E3 ligases were also found to play important roles in regulating fruit size.…”