Two types of cinnamoyl-CoA reductase function divergently in accumulation of lignins, flavonoids and glucosinolates and enhance lodging resistance in Brassica napus

Abstract

Brassica crops, which are of worldwide importance, provide various oil, vegetable and ornamental products, as well as feedstocks for animal husbandry and biofuel industry. Cinnamoyl-CoA reductase (CCR) is the entry point to the lignin pathway and a crucial locus in manipulation of associated traits, but CCR-associated metabolism and traits in Brassica crops have remained largely unstudied except in Arabidopsis thaliana. We report the identification of 16 CCR genes from Brassica napus and its parental species B. rapa and B. oleracea. The BnCCR1 and BnCCR2 subfamilies displayed divergent organ-specificity and participation in the yellow-seed trait. Their functions were dissected via overexpression of representative paralogs in B. napus. BnCCR1 was expressed preferentially in G- and H-lignin biosynthesis and vascular development, while BnCCR2 was expressed in S-lignin biosynthesis and interfascicular fiber development. BnCCR1 showed stronger effects on lignification-related development, lodging resistance, phenylpropanoid flux control, and seed coat pigmentation, whereas BnCCR2 showed a stronger effect on sinapate biosynthesis. BnCCR1 upregulation delayed bolting and flowering time, while BnCCR2 upregulation weakened the leaf vascular system in consequence of suppressed G-lignin accumulation. BnCCR1 and BnCCR2 were closely but almost oppositely linked with glucosinolate metabolism via inter-pathway crosstalk. We conclude that BnCCR1 and BnCCR2 subfamilies offer great but differing potential for manipulating traits associated with phenylpropanoids and glucosinolates. This study reveals the CCR1–CCR2 divergence in Brassicaceae and offers a resource for rapeseed breeding for lodging resistance, yellow-seed traits, and glucosinolate traits.