Institute of Molecular Physiology and Biotechnology of Plants (IMBIO), Faculty of Natural Sciences, University of Bonn, Kirschallee 1, Bonn, D-53115, Germany.
Centre for Plant Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK.
Plant J. 2019 Nov;100(4):661-676. doi: 10.1111/tpj.14479. Epub 2019 Sep 15.
Craterostigma plantagineum belongs to the desiccation-tolerant angiosperm plants. Upon dehydration, leaves fold and the cells shrink which is reversed during rehydration. To understand this process changes in cell wall pectin composition, and the role of the apoplastic glycine-rich protein 1 (CpGRP1) were analysed. Cellular microstructural changes in hydrated, desiccated and rehydrated leaf sections were analysed using scanning electron microscopy. Pectin composition in different cell wall fractions was analysed with monoclonal antibodies against homogalacturonan, rhamnogalacturonan I, rhamnogalacturonan II and hemicellulose epitopes. Our data demonstrate changes in pectin composition during dehydration/rehydration which is suggested to affect cell wall properties. Homogalacturonan was less methylesterified upon desiccation and changes were also demonstrated in the detection of rhamnogalacturonan I, rhamnogalacturonan II and hemicelluloses. CpGRP1 seems to have a central role in cell adaptations to water deficit, as it interacts with pectin through a cluster of arginine residues and de-methylesterified pectin presents more binding sites for the protein-pectin interaction than to pectin from hydrated leaves. CpGRP1 can also bind phosphatidic acid (PA) and cardiolipin. The binding of CpGRP1 to pectin appears to be dependent on the pectin methylesterification status and it has a higher affinity to pectin than its binding partner CpWAK1. It is hypothesised that changes in pectin composition are sensed by the CpGRP1-CpWAK1 complex therefore leading to the activation of dehydration-related responses and leaf folding. PA might participate in the modulation of CpGRP1 activity.
肿柄菊属植物属于耐旱型被子植物。脱水时，叶子会折叠，细胞会收缩，在重新水合时又会恢复。为了了解这个过程中细胞壁果胶组成的变化，以及质外体富含甘氨酸的蛋白 1 (CpGRP1) 的作用，我们进行了分析。利用扫描电子显微镜分析了水合、脱水和再水合叶片切片的细胞微观结构变化。使用针对同型半乳糖醛酸、鼠李半乳糖醛酸 I、鼠李半乳糖醛酸 II 和半纤维素表位的单克隆抗体分析了不同细胞壁级分中的果胶组成。我们的数据表明，在脱水/再水合过程中果胶组成发生了变化，这可能会影响细胞壁特性。在脱水时，同型半乳糖醛酸甲酯化程度降低，鼠李半乳糖醛酸 I、鼠李半乳糖醛酸 II 和半纤维素的检测也发生了变化。CpGRP1 似乎在细胞适应水分亏缺方面起着核心作用，因为它通过精氨酸残基簇与果胶相互作用，而去甲酯化的果胶比水合叶片中的果胶具有更多的蛋白-果胶相互作用结合位点。CpGRP1 还可以结合磷脂酸 (PA) 和心磷脂。CpGRP1 与果胶的结合似乎依赖于果胶的甲酯化状态，它与果胶的结合亲和力高于其结合伙伴 CpWAK1。我们假设果胶组成的变化被 CpGRP1-CpWAK1 复合物感知，从而导致与脱水相关的反应和叶片折叠的激活。PA 可能参与调节 CpGRP1 活性。
