Catechins are critical constituents
for the sensory quality and
health-promoting benefits of tea. Cytochrome P450 monooxygenases are
required for catechin biosynthesis and are dependent on NADPH-cytochrome
P450 reductases (CPRs) to provide reducing equivalents for their activities.
However, CPRs have not been identified in tea, and their relationship
to catechin accumulation also remains unknown. Thus, three CsCPR genes were identified in this study, all of which
had five CPR-related conserved domains and were targeted to the endoplasmic
reticulum. These three recombinant CsCPR proteins
could reduce cytochrome c using NADPH as an electron
donor. Heterologous co-expression in yeast demonstrated that all the
three CsCPRs could support the enzyme activities
of CsC4H and CsF3′H. Correlation
analysis indicated that the expression level of CsCPR1 (or CsCPR2 or CsCPR3) was positively
correlated with 3′,4′,5′-catechin (or total catechins)
content. Our results indicate that the CsCPRs are
involved in the biosynthesis of catechins in tea leaves.