| Summary: | Cinnamoyl-CoA reductases (CCR) have a possible role in pungency formation of pepper because they can convert feruloyl-CoA, sinapoyl-CoA, and p-coumaroyl-CoA into lignin, which are also competitive precursors of capsaicin biosynthesis in phenylpropanoid metabolism. In this study, genome-wide <i>CCR</i> gene family, exon–intron structures, sequence homology, phylogenetic characterization, and promoters were analyzed in pepper. Two <i>CCR</i> genes were cloned from <i>Capsicum chinense</i>, their enzymic kinetic parameters and regulatory function were identified by heterologous expression, ectopic expression, and VIGS. In total, 38 genes were found as predicted CCRs or CCR-like proteins and were composed of 2–10 exons. The promoters of pepper <i>CCRs</i> contained growth, stress, hormone, and light-response elements. The affinity and catalytic efficiency of CcCCR1/2 to feruolyl-CoA was the highest. The analysis of metabolic substances showed that capsaicin content was negatively correlated with lignin and positively correlated with flavonoids. The highest expression of <i>CcCCR1</i> was found in stems, the higher expression of <i>CcCCR2</i> was found in stem and early fruit than other organs. <i>CCR1</i><i>, 2</i> had certain effects on capsaicin content by regulating related enzyme activity, <i>CCR2</i> played a more important role in regulating pungency formation. Our results clarify the competitive mechanism between lignin and capsaicin biosynthesis and provide an explanation for spice regulation.
|
|---|