Cinnamoyl-CoA Reductase 1 (CCR1) and CCR2 Function Divergently in Tissue Lignification, Flux Control and Cross-talk with Glucosinolate Pathway in Brassica napus

Cinnamoyl-CoA reductase (CCR) is the entry point of lignin pathway and a crucial locus in dissection and manipulation of associated traits, but its functional dissection in Brassicaceae plants is largely lagged behind though Arabidopsis thaliana CCR1 has been characterized to certain extent. Here, 16 CCR genes are identified from Brassica napus and its parental species B. rapa and B. oleracea. Brassicaceae CCR genes are divided into CCR1 subfamily and CCR2 subfamily with divergent organ-specificity, yellow-seed trait participation and stresses responsiveness. CCR1 is preferential in G- and H-lignins biosynthesis and vascular development, while CCR2 has a deviation to S-lignin biosynthesis and interfascicular fiber development. CCR1 has stronger effects on lignification-related development, lodging resistance, phenylpropanoid flux control and seed coat pigmentation, whereas CCR2 controls sinapates levels. CCR1 upregulation could delay bolting and flowering time, while CCR2 upregulation weakens vascular system in leaf due to suppressed G lignin accumulation. Besides, CCR1 and CCR2 are deeply but almost oppositely linked with glucosinolates metabolism through inter-pathway crosstalk. Strangely, upregulation of both CCR1 and CCR2 could not enhance resistance to UV-B and S. sclerotiorum though CCR2 is sharply induced by them. These results provide systemic dissection on Brassica CCRs and CCR1-CCR2 divergence in Brassicaceae. HighlightBrassicaceae contains two types of Cinnamoyl-CoA reductase. As revealed in Brassica napus, they are divergently involved in lignin monomer biosynthesis, tissue lignification, phenylpropanoid flux control, and inter-pathway crosstalk with glucosinolates.