College of Life Sciences, Northwest A&F University, Yangling, China.
Biomass Energy Center for Arid and Semi-arid Lands, Northwest A&F University, Yangling, China.
J Exp Bot. 2021 Feb 24;72(4):1073-1084. doi: 10.1093/jxb/eraa533.
The primary cell walls of plants provide mechanical strength while maintaining the flexibility needed for cell extension growth. Cell extension involves loosening the bonds between cellulose microfibrils, hemicelluloses and pectins. Pectins have been implicated in this process, but it remains unclear if this depends on the abundance of certain pectins, their modifications, and/or structure. Here, cell wall-related mutants of the model plant Arabidopsis were characterized by biochemical and immunohistochemical methods and Fourier-transform infrared microspectroscopy. Mutants with reduced pectin or hemicellulose content showed no root cell elongation in response to simulated drought stress, in contrast to wild-type plants or mutants with reduced cellulose content. While no association was found between the degrees of pectin methylesterification and cell elongation, cell wall composition analysis suggested an important role of the pectin rhamnogalacturonan II (RGII), which was corroborated in experiments with the RGII-modifying chemical 2β-deoxy-Kdo. The results were complemented by expression analysis of cell wall synthesis genes and microscopic analysis of cell wall porosity. It is concluded that a certain amount of pectin is necessary for stress-induced root cell elongation, and hypotheses regarding the mechanistic basis of this result are formulated.
植物的初生细胞壁提供机械强度，同时保持细胞延伸生长所需的柔韧性。细胞延伸涉及到纤维素微纤维、半纤维素和果胶之间键的松动。果胶在这个过程中起作用，但尚不清楚这是否取决于特定果胶的丰度、它们的修饰和/或结构。在这里，通过生化和免疫组织化学方法以及傅里叶变换红外微光谱学对模式植物拟南芥的细胞壁相关突变体进行了表征。与野生型植物或纤维素含量降低的突变体相比，果胶或半纤维素含量降低的突变体在模拟干旱胁迫下没有根细胞伸长。虽然果胶甲酯化程度与细胞伸长之间没有关联，但细胞壁成分分析表明果胶鼠李半乳糖醛酸 II（RGII）起着重要作用，这在使用 RGII 修饰化学物质 2β-去氧-Kdo 的实验中得到了证实。结果通过细胞壁合成基因的表达分析和细胞壁孔隙率的显微镜分析得到补充。结论是一定量的果胶对于应激诱导的根细胞伸长是必要的，并提出了关于这一结果的机制基础的假设。
