Exploiting CELLULOSE SYNTHASE (CESA) Class Specificity to Probe Cellulose Microfibril Biosynthesis
Exploiting CELLULOSE SYNTHASE (CESA) Class Specificity to Probe Cellulose Microfibril Biosynthesis
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DOI：
10.1104/pp.18.00263
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发表时间：
2018-05-01
期刊：
影响因子：
7.4
通讯作者：
Turner, Simon
中科院分区：
文献类型：
--
作者：
Kumar, Manoj;Mishra, Laxmi;Turner, Simon
纤维素微纤丝是植物中纤维素的基本单位。这些微纤丝的结构至少部分地由纤维素合酶复合物的结构决定。在高等植物中，这种复合物由18至24个催化亚基组成，称为纤维素合成酶A（CESA）蛋白。纤维素合成和次生细胞壁纤维素生物合成需要三种不同类别的CESA蛋白，这些类别由CESA 4、CESA 7和CESA 8代表。为了探测CESA蛋白和微纤维结构之间的关系，我们创建了突变CESA蛋白，其缺乏催化活性，但保留足够的结构完整性以允许纤维素合酶复合物的组装。使用一系列的拟南芥（拟南芥）突变体和遗传背景，我们发现一致的差异，这些突变cesa蛋白的能力，以补充cesa无效突变体的纤维素缺乏表型。最好的互补与催化失活cesa4观察，而在cesa8的等效突变表现出显着较低的互补水平。使用各种生物物理技术，包括固态核磁共振和傅里叶变换红外显微镜，研究这些突变体植物，我们发现纤维素微纤丝结构变化的证据，但这些变化在很大程度上与纤维素含量和反映的差异在相对比例的初级和次级细胞壁。我们的研究结果表明，个别CESA类在确定纤维素微纤维结构中具有相似的作用，并且很可能不同CESA类的突变成员的不同影响是其不同催化活性及其对纤维素合成的总体速率的影响的结果。
Cellulose microfibrils are the basic units of cellulose in plants. The structure of these microfibrils is at least partly determined by the structure of the cellulose synthase complex. In higher plants, this complex is composed of 18 to 24 catalytic subunits known as CELLULOSE SYNTHASE A (CESA) proteins. Three different classes of CESA proteins are required for cellulose synthesis and for secondary cell wall cellulose biosynthesis these classes are represented by CESA4, CESA7, and CESA8. To probe the relationship between CESA proteins and microfibril structure, we created mutant cesa proteins that lack catalytic activity but retain sufficient structural integrity to allow assembly of the cellulose synthase complex. Using a series of Arabidopsis (Arabidopsis thaliana) mutants and genetic backgrounds, we found consistent differences in the ability of these mutant cesa proteins to complement the cellulose-deficient phenotype of the cesa null mutants. The best complementation was observed with catalytically inactive cesa4, while the equivalent mutation in cesa8 exhibited significantly lower levels of complementation. Using a variety of biophysical techniques, including solid-state nuclear magnetic resonance and Fourier transform infrared microscopy, to study these mutant plants, we found evidence for changes in cellulose microfibril structure, but these changes largely correlated with cellulose content and reflected differences in the relative proportions of primary and secondary cell walls. Our results suggest that individual CESA classes have similar roles in determining cellulose microfibril structure, and it is likely that the different effects of mutating members of different CESA classes are the consequence of their different catalytic activity and their influence on the overall rate of cellulose synthesis.