Decreased seed oil production in FUSCA3 Brassica napus mutant plants

Canola (Brassica napus L.) oil is extensively utilized for human consumption and industrial applications. Among the genes regulating seed development and participating in oil accumulation is FUSCA3 (FUS3), a member of the plant-specific B3-domain family of transcription factors. To evaluate the role of this gene during seed storage deposition, three BnFUSCA3 (BnFUS3) TILLING mutants were generated. Mutations occurring downstream of the B3 domain reduced silique number and repressed seed oil level resulting in increased protein content in developing seeds. BnFUS3 mutant seeds also had increased levels of linoleic acid, possibly due to the reduced expression of ω-3 FA DESATURASE (FAD3). These observed phenotypic alterations were accompanied by the decreased expression of genes encoding transcription factors stimulating fatty acid (FA) synthesis: LEAFY COTYLEDON1 and 2 (LEC1 and 2) ABSCISIC ACID-INSENSITIVE 3 (BnABI3) and WRINKLED1 (WRI1). Additionally, expression of genes encoding enzymes involved in sucrose metabolism, glycolysis, and FA modifications were down-regulated in developing seeds of the mutant plants. Collectively, these transcriptional changes support altered sucrose metabolism and reduced glycolytic activity, diminishing the carbon pool available for the synthesis of FA and ultimately seed oil production. Based on these observations, it is suggested that targeted manipulations of BnFUS3 can be used as a tool to influence oil accumulation in the economically important species B. napus.