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Title: Cinnamic acid 4-hydroxylase of sorghum [Sorghum biocolor (L.) Moench] gene SbC4H1 restricts lignin synthesis in Arabidopsis

Author
item YAN, LI - Shandong University
item XIA, GUANGMIN - Shandong University
item Huang, Yinghua
item ZAHO, SHUANGYI - Shandong University

Submitted to: Plant Physiology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/14/2013
Publication Date: 12/1/2013
Citation: Yan, L., Xia, G., Huang, Y., Zaho, S. 2013. Cinnamic acid 4-hydroxylase of sorghum [Sorghum biocolor (L.) Moench] gene SbC4H1 restricts lignin synthesis in Arabidopsis. Plant Physiology Journal. 49(12):1433-1441.

Interpretive Summary: Sorghum is currently being developed as a biofuel crop. One of our research goals is to improve sorghum for easier conversion of its lignocellulosic biomass into bioethanol. Lignin and cellulose are the major components of the lignocellulosic biomass but lignin is a key barrier in the conversion of plant biomass to bioethanol. It is assumed that plant biomass with reduced lignin content can be easily converted to the liquid fuel at a low cost. In our recent study, we have produced the first comprehensive transcriptomic analysis of lignin biosynthesis-related genes in a mutant (BMR) line of sorghum. From this study, an important lignin biosynthesis gene coding for cinnamic acid 4-hydroxylase (C4H), the first hydroxylase enzyme of the phenylpropanoid pathway, was identified as it was differentially expressed in the lignin-mutant line compared to its wild-type counterpart. The results obtained from molecular characterization of the gene indicated that this gene (bC4H1) plays an important role in down-regulation of other important genes in the lignin biosynthetic pathway. In summary, the SbC4H1 gene can serve as the candidate gene to regulate lignin content in sorghum and other sophisticated biofuel plants.

Technical Abstract: Cinnamic acid 4-hydroxylase (C4H) is the first hydroxylase enzyme of the phenylpropanoid pathway, and its content and activity affects the lignin synthesis. In this study, we isolated a C4H gene SbC4H1 from the suppression subtractive hybridization library of brown midrib (bmr) mutants of Sorghum bicolor. Semiquantitative RT-PCR (sqRT-PCR) analysis showed that SbC4H1 was up-regulated in most of bmr mutants. The transient expression assay in Arabidopsis protoplast indicated SbC4H1 was mainly located in the cytoplasm. Ectopic overexpression of SbC4H1 significantly lowered the content of lignin in Arabidopsis. sqRT-PCR indicated that several genes in phenylpropanoid pathway such as 4CL1, F5H1 and HCT were down-regulated in Arabidopsis. These results showed that, SbC4H1 played an inhibitory effect on the synthesis of lignin.