RESEARCH ARTICLE
. Key Laboratory of Energy Genetics of Shandong Province/Qingdao Engineering Research Center of Biomass Resources and Environment/Key Laboratory of Biofuels/Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao 266101, China.. Tobacco Research Institute, Chinese Academy of Agricultural Sciences, Qingdao 266101, China.. Forage Improvement Division, The Samuel Roberts Noble Foundation, Ardmore, OK73401, USA
录用日期：
2018-02-08
发布日期：
2018-03-21
摘要
Caffeic acid -methyltransferase (COMT) is a crucial enzyme that mainly methylates phenylpropanoid -hydroxyl of C in the biosynthesis of syringyl lignin in angiosperms. A putative , named as , was isolated from switchgrass ( ), a C warm-season dual-purpose forage and bioenergy crop. Our results showed that recombinant PvCOMT1 enzyme protein catalyzed the methylation of 5-OH coniferyl alcohol, 5-OH coniferaldehyde (CAld5H) and 5-OH ferulic acid. Further studies indicate that CAld5H can dominate COMT-mediated reactions by inhibiting the methylation of the other substrates. Transgenic switchgrass plants generated by an RNAi approach were further employed to study the function of in internode lignification. A dramatic decrease in syringyl lignin units coupled with an obvious incorporation in 5-OH guaiacyl lignin units were observed in the COMT-RNAi transgenic plants. However, the constitutive suppression of COMT in switchgrass plants altered neither the pattern of lignin deposition along the stem nor the anatomical structure of internodes. Consistent with the biochemical characterization of PvCOMT1, a significant decrease in sinapaldehyde was found in the COMT-RNAi transgenic switchgrass plants, suggesting that CAld5H could be the optimal intermediate in the biosynthesis syringyl lignin.
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