JXB Advance Access originally published online on April 23, 2007
Journal of Experimental Botany 2007 58(8):2011-2021; doi:10.1093/jxb/erm064
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RESEARCH PAPER |
Characterization of a cinnamoyl-CoA reductase that is associated with stem development in wheat
Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, 20 Nanxin Cun, Xiangshan, Beijing 100093, China
* To whom correspondence should be addressed. E-mail: mqh{at}ibcas.ac.cn
Cinnamoyl-CoA reductase (CCR) is responsible for the CoA ester to aldehyde conversion in monolignol biosynthesis, which diverts phenylpropanoid-derived metabolites into the biosynthesis of lignin. To gain a better understanding of lignin biosynthesis and its biological function, a cDNA encoding CCR was identified from wheat (Triticum aestivum L.), and designated as Ta-CCR1. Phylogenetic analysis indicated that Ta-CCR1 grouped together with other monocot CCR sequences while it diverged from Ta-CCR2. DNA gel-blot and mapping analyses demonstrated that Ta-CCR1 is present as a single copy gene in the wheat genome. Recombinant Ta-CCR1 protein converted feruloyl CoA, 5-OH-feruloyl CoA, sinapoyl CoA, and caffeoyl CoA, but feruloyl-CoA was the best substrate, suggesting the preferential biosynthesis of G-type lignin. RNA gel-blot analysis indicated that Ta-CCR1 was highly expressed in stem, with lower expression in leaves, and undetectable expression in roots. CCR enzyme activity was increased progressively along with the lignin biosynthesis and stem maturity. During stem development, Ta-CCR1 mRNA levels remained high at elongation, heading, and milky stages in the wheat H4564 cultivar, while they declined dramatically at the heading and milky stages in stems of the C6001 cultivar. Ta-CCR1 mRNA expression paralleled extractable CCR enzyme activity in these two cultivars. Furthermore, high Ta-CCR1 mRNA levels and high CCR enzyme activity in wheat stem were correlated with a higher Klason lignin content and greater stem mechanical strength in the H4564 cultivar. This suggests that Ta-CCR1 and its related CCR enzyme may be involved in the regulation of lignin biosynthesis during stem maturity and then contributes to stem strength support in wheat.
Key words: Cinnamoyl-CoA reductase, lignin biosynthesis, stem strength support, Triticum aestivum L
Received 21 November 2006; Revised 28 January 2007 Accepted 6 March 2007
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