Downregulation of p‐COUMAROYL ESTER 3‐HYDROXYLASE in rice leads to altered cell wall structures and improves biomass saccharification
Downregulation of p‐COUMAROYL ESTER 3‐HYDROXYLASE in rice leads to altered cell wall structures and improves biomass saccharification
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DOI：
10.1111/tpj.13988
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发表时间：
2018-07
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通讯作者：
Yuri Takeda;Y. Tobimatsu;S. D. Karlen;Taichi Koshiba;Shiro Suzuki;M. Yamamura;S. Murakami;M. Mukai;T. Hattori;K. Osakabe;J. Ralph;M. Sakamoto;T. Umezawa
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作者：
Yuri Takeda;Y. Tobimatsu;S. D. Karlen;Taichi Koshiba;Shiro Suzuki;M. Yamamura;S. Murakami;M. Mukai;T. Hattori;K. Osakabe;J. Ralph;M. Sakamoto;T. Umezawa
对香豆酰酯3-羟化酶（C3 ′ H）是参与木质素生物合成的关键酶，木质素是一种苯丙素类聚合物，是维管植物次生细胞壁的主要成分。虽然C3 'H在木质化中的关键作用及其对木质纤维素升级的操纵已经在真双子叶植物中进行了研究，但在单子叶草物种中可获得的信息有限，尽管它们具有作为生物质原料的潜力。在这里，我们解决的C3 'H缺乏对草细胞壁的结构和性能的显着影响。通过RNA干扰（RNAi）介导的基因沉默产生的C3 'H-敲低株系，具有约0.5%的残余表达水平，达到成熟并结籽。相比之下，通过CRISPR/Cas9介导的诱变产生的C3 'H敲除水稻突变体严重矮化和不育。成熟的C3 'H-敲低RNAi系的细胞壁分析揭示，它们的木质素主要富集对羟基苯基（H）单元，而在通常占优势的愈创木基（G）和胡萝卜基（S）单元中显著减少。然而，有趣的是，H单元的富集限于非酰化木质素单元内，而草特异性γ-对香豆酰化木质素单元保持明显不变。抑制C3 'H也导致相对增加麦黄酮残基在木质素以及大量减少壁交联阿魏酸。总的来说，我们的数据表明，C3 'H的表达是一个重要的决定因素，不仅木质素含量和组成，而且细胞壁交联的程度。我们还证明了C3 'H抑制的水稻显示出增强的生物质糖化。
p-Coumaroyl ester 3-hydroxylase (C3'H) is a key enzyme involved in the biosynthesis of lignin, a phenylpropanoid polymer that is the major constituent of secondary cell walls in vascular plants. Although the crucial role of C3'H in lignification and its manipulation to upgrade lignocellulose have been investigated in eudicots, limited information is available in monocotyledonous grass species, despite their potential as biomass feedstocks. Here we address the pronounced impacts of C3'H deficiency on the structure and properties of grass cell walls. C3'H-knockdown lines generated via RNA interference (RNAi)-mediated gene silencing, with about 0.5% of the residual expression levels, reached maturity and set seeds. In contrast, C3'H-knockout rice mutants generated via CRISPR/Cas9-mediated mutagenesis were severely dwarfed and sterile. Cell wall analysis of the mature C3'H-knockdown RNAi lines revealed that their lignins were largely enriched in p-hydroxyphenyl (H) units while being substantially reduced in the normally dominant guaiacyl (G) and syringyl (S) units. Interestingly, however, the enrichment of H units was limited to within the non-acylated lignin units, with grass-specific γ-p-coumaroylated lignin units remaining apparently unchanged. Suppression of C3'H also resulted in relative augmentation in tricin residues in lignin as well as a substantial reduction in wall cross-linking ferulates. Collectively, our data demonstrate that C3'H expression is an important determinant not only of lignin content and composition but also of the degree of cell wall cross-linking. We also demonstrated that C3'H-suppressed rice displays enhanced biomass saccharification.