Faculty of Biotechnology, University of Wroclaw, Przybyszewskiego 63/77, Wroclaw 51-148, Poland.
BMC Plant Biol. 2014 Feb 20;14:50. doi: 10.1186/1471-2229-14-50.
In recent decades cultivation of flax and its application have dramatically decreased. One of the reasons for this is unpredictable quality and properties of flax fibre, because they depend on environmental factors, retting duration and growing conditions. These factors have contribution to the fibre composition, which consists of cellulose, hemicelluloses, lignin and pectin. By far, it is largely established that in flax, lignin reduces an accessibility of enzymes either to pectin, hemicelluloses or cellulose (during retting or in biofuel synthesis and paper production).Therefore, in this study we evaluated composition and properties of flax fibre from plants with silenced CAD (cinnamyl alcohol dehydrogenase) gene, which is key in the lignin biosynthesis. There is evidence that CAD is a useful tool to improve lignin digestibility and/or to lower the lignin levels in plants.
Two studied lines responded differentially to the introduced modification due to the efficiency of the CAD silencing. Phylogenetic analysis revealed that flax CAD belongs to the "bona-fide" CAD family. CAD down-regulation had an effect in the reduced lignin amount in the flax fibre cell wall and as FT-IR results suggests, disturbed lignin composition and structure. Moreover introduced modification activated a compensatory mechanism which was manifested in the accumulation of cellulose and/or pectin. These changes had putative correlation with observed improved fiber's tensile strength. Moreover, CAD down-regulation did not disturb at all or has only slight effect on flax plants' development in vivo, however, the resistance against flax major pathogen Fusarium oxysporum decreased slightly. The modification positively affected fibre possessing; it resulted in more uniform retting.
The major finding of our paper is that the modification targeted directly to block lignin synthesis caused not only reduced lignin level in fibre, but also affected amount and organization of cellulose and pectin. However, to conclude that all observed changes are trustworthy and correlated exclusively to CAD repression, further analysis of the modified plants genome is necessary. Secondly, this is one of the first studies on the crop from the low-lignin plants from the field trail which demonstrates that such plants could be successfully cultivated in a field.
近几十年来，亚麻的种植和应用显著减少。造成这种情况的原因之一是亚麻纤维的质量和性能不可预测，因为它们取决于环境因素、沤麻时间和生长条件。这些因素会影响纤维的组成，包括纤维素、半纤维素、木质素和果胶。到目前为止，人们已经充分认识到，在亚麻中，木质素会降低酶对果胶、半纤维素或纤维素的可及性（在沤麻或生物燃料合成和造纸过程中）。因此，在这项研究中，我们评估了来自沉默 CAD（肉桂醇脱氢酶）基因的植物的亚麻纤维的组成和性质，CAD 基因是木质素生物合成的关键。有证据表明，CAD 是提高木质素消化率和/或降低植物木质素水平的有用工具。
由于 CAD 沉默的效率，两条研究线对引入的修饰表现出不同的反应。系统发育分析表明，亚麻 CAD 属于“名副其实”的 CAD 家族。CAD 下调对亚麻纤维细胞壁中木质素含量的减少有影响，并且如傅里叶变换红外光谱（FT-IR）结果所示，木质素的组成和结构受到干扰。此外，引入的修饰激活了一种补偿机制，表现为纤维素和/或果胶的积累。这些变化与观察到的纤维拉伸强度的提高有潜在的相关性。此外，CAD 下调在体内对亚麻植物的生长没有干扰或只有轻微的影响，但对亚麻主要病原体尖孢镰刀菌的抗性略有下降。这种修饰对纤维有积极的影响；它导致更均匀的沤麻。
本文的主要发现是，直接针对木质素合成的修饰不仅导致纤维中木质素水平降低，而且还影响纤维素和果胶的含量和组织。然而，要得出所有观察到的变化都是可靠的，并且仅与 CAD 抑制相关的结论，还需要对修饰植物的基因组进行进一步分析。其次，这是对田间低木质素作物的首次研究之一，证明了这种植物可以在田间成功种植。
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