Disrupting the cinnamyl alcohol dehydrogenase 1 gene (BdCAD1) leads to altered lignification and improved saccharification in Brachypodium distachyon
Disrupting the cinnamyl alcohol dehydrogenase 1 gene (BdCAD1) leads to altered lignification and improved saccharification in Brachypodium distachyon
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DOI：
10.1111/tpj.12053
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发表时间：
2013-02-01
期刊：
影响因子：
7.2
通讯作者：
Sibout, Richard
中科院分区：
文献类型：
--
作者：
d'Yvoire, Madeleine Bouvier;Bouchabke-Coussa, Oumaya;Sibout, Richard
二穗短柄草（Brachypodium distachyon）已被提议作为禾本科植物的模式，但关于其木质素的知识有限，也没有关于木质素相关突变体的数据。参与木质化的肉桂醇脱氢酶（CAD）基因是改善纤维素转化为乙醇过程的有前途的目标。CAD的下调通常诱导韧带组织的红色着色。基于这一观察结果，我们筛选了化学诱导的短柄草突变体群体（Bd 213背景）的红色秆着色。我们鉴定了两个突变体（Bd 4179和Bd 7591），其在BdCAD 1基因中具有突变。这些突变体的成熟茎表现出降低CAD活性和较低的木质素含量。它们的木质素富含8 O 4-和4 O 5-偶联的芥子醛单元，以及抗性单元间键和游离酚基。相比之下，松柏醛端基没有增加。此外，芥子酸酯连接到细胞壁的量首次在木质素相关的CAD草突变体中测量。Bd 4179突变体与野生型BdCAD 1等位基因的功能互补恢复了野生型表型和木质化。纯化试验表明，Bd 4179和Bd 7591系比野生型植物更容易被酶水解。在这里，我们已经证明，BdCAD 1参与短柄草的木质化。我们已经表明，BdCAD 1中的单个核苷酸变化降低了木质素水平，并通过掺入芥子醛增加了木质素的支化程度。这些变化使得用碱预处理的细胞壁的糖化更容易，而不损害植物生长。
Brachypodium distachyon (Brachypodium) has been proposed as a model for grasses, but there is limited knowledge regarding its lignins and no data on lignin-related mutants. The cinnamyl alcohol dehydrogenase (CAD) genes involved in lignification are promising targets to improve the cellulose-to-ethanol conversion process. Down-regulation of CAD often induces a reddish coloration of lignified tissues. Based on this observation, we screened a chemically induced population of Brachypodium mutants (Bd213 background) for red culm coloration. We identified two mutants (Bd4179 and Bd7591), with mutations in the BdCAD1 gene. The mature stems of these mutants displayed reduced CAD activity and lower lignin content. Their lignins were enriched in 8O4- and 4O5-coupled sinapaldehyde units, as well as resistant inter-unit bonds and free phenolic groups. By contrast, there was no increase in coniferaldehyde end groups. Moreover, the amount of sinapic acid ester-linked to cell walls was measured for the first time in a lignin-related CAD grass mutant. Functional complementation of the Bd4179 mutant with the wild-type BdCAD1 allele restored the wild-type phenotype and lignification. Saccharification assays revealed that Bd4179 and Bd7591 lines were more susceptible to enzymatic hydrolysis than wild-type plants. Here, we have demonstrated that BdCAD1 is involved in lignification of Brachypodium. We have shown that a single nucleotide change in BdCAD1 reduces the lignin level and increases the degree of branching of lignins through incorporation of sinapaldehyde. These changes make saccharification of cells walls pre-treated with alkaline easier without compromising plant growth.