Two cinnamoyl-CoA reductase (CCR) genes from Arabidopsis thaliana are differentially expressed during development and in response to infection with pathogenic bacteria

Cinnamoyl-CoA reductase (CCR; EC 1.2.1.44) catalyses the conversion of cinn amoyl-CoAs into their corresponding cinnamaldehydes, i.e. the first step of the phenylpropanoid pathway specifically dedicated to the monolignol biosy nthetic branch. In previous work. we described the isolation and characteri sation of the: first cDNA encoding CCR in Eucalyptus (Lacombe, E., Hawkins, S,, Van Dorsselaere, J., Piquemal, J,, Goffner, D., Poeydomenge, O., Boude t, A.M., Grima-Pettenati, J., 1997. Cinnamoyl CoA reductase, the first comm itted enzyme of the lignin branch biosynthetic pathway: cloning, expression and phylogenetic relationships. Plant Journal 11, 429-441) and shown the r ole of this enzyme in controlling the carbon flux into lignins (Piquemal, J ., Lapierre, C., Myton, It., O'Connell, A., Schuch, W., Grima-Pettenati, J. , Boudet, A.M., 1998, Down-regulation of cinnamoyl-CoA reductase induces si gnificant changes of lignin profiles in transgenic tobacco plants. Plant Jo urnal 13, 71-83). Here, we report the characterisation of two functionally and structurally distinct cDNA clones, AtCCR1 and AtCCR2 (81.6% protein seq uence identity) in Arabidopsis thaliana. The two recombinant proteins expre ssed in Escherichia coli are able to use the three cinnamoyl-CoAs tested bu t with different levels of efficiency. AtCCR1 is five times more efficient with feruloyl-CoA and sinapoyl-CoA than AtCCR2. In addition, the two genes are differentially expressed during development and in response to infectio n. AtCCR1 is preferentially expressed in tissues undergoing lignification. In contrast, AtCCR2, which is poorly expressed during development, is stron gly and transiently induced during the incompatible interaction with;Xantho monas campestris pv. campestris leading to a hypersensitive response. Altog ether, these data suggest that AtCCR1 is involved in constitutive lignifica tion whereas AtCCR2 is involved in the biosynthesis of phenolics whose accu mulation may lead to resistance. (C) 2001 Elsevier Science Ltd. All rights reserved.