Reem Nathan T, Chambers Lauran, Zhang Ning, Abdullah Siti Farah, Chen Yintong, Feng Guanhua, Gao Song, Soto-Burgos Junmarie, Pogorelko Gennady, Bassham Diane C, Anderson Charles T, Walley Justin W, Zabotina Olga A
Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, IA 50011, USA.
Department of Biology, The Pennsylvania State University, University Park, PA 16802, USA.
Plants (Basel). 2020 Nov 12;9(11):1558. doi: 10.3390/plants9111558.
Pectin is a critical component of the plant cell wall, supporting wall biomechanics and contributing to cell wall signaling in response to stress. The plant cell carefully regulates pectin methylesterification with endogenous pectin methylesterases (PMEs) and their inhibitors (PMEIs) to promote growth and protect against pathogens. We expressed pectin methylesterase (AnPME) in plants to determine the impacts of methylesterification status on pectin function. Plants expressing AnPME had a roughly 50% reduction in methylester content compared with control plants. AnPME plants displayed a severe dwarf phenotype, including small, bushy rosettes and shorter roots. This phenotype was caused by a reduction in cell elongation. Cell wall composition was altered in AnPME plants, with significantly more arabinose and significantly less galacturonic acid, suggesting that plants actively monitor and compensate for altered pectin content. Cell walls of AnPME plants were more readily degraded by polygalacturonase (PG) alone but were less susceptible to treatment with a mixture of PG and PME. AnPME plants were insensitive to osmotic stress, and their susceptibility to was comparable to wild type plants despite their compromised cell walls. This is likely due to upregulated expression of defense response genes observed in AnPME plants. These results demonstrate the importance of pectin in both normal growth and development, and in response to biotic and abiotic stresses.
果胶是植物细胞壁的关键成分，支撑细胞壁的生物力学，并在植物应对胁迫时参与细胞壁信号传导。植物细胞通过内源性果胶甲酯酶（PMEs）及其抑制剂（PMEIs）精确调控果胶甲基酯化，以促进生长并抵御病原体。我们在植物中表达果胶甲酯酶（AnPME），以确定甲基酯化状态对果胶功能的影响。与对照植物相比，表达AnPME的植物甲酯含量降低了约50%。AnPME植物表现出严重的矮化表型，包括小而浓密的莲座叶丛和较短的根。这种表型是由细胞伸长减少引起的。AnPME植物的细胞壁组成发生了改变，阿拉伯糖显著增多，半乳糖醛酸显著减少，这表明植物会主动监测并补偿果胶含量的变化。AnPME植物的细胞壁仅用聚半乳糖醛酸酶（PG）就能更轻易地降解，但对PG和PME混合物的处理不太敏感。AnPME植物对渗透胁迫不敏感，尽管其细胞壁受损，但其对病原体的易感性与野生型植物相当。这可能是由于在AnPME植物中观察到防御反应基因的表达上调。这些结果证明了果胶在正常生长发育以及应对生物和非生物胁迫中的重要性。
