Wang Pengfei, Kang Byung-Ho
a Cellular and Molecular Biology Program, State Key Laboratory of Agrobiotechnology, School of Life Sciences , The Chinese University of Hong Kong , Hong Kong , China.
Plant Signal Behav. 2018;13(8):e1469362. doi: 10.1080/15592324.2018.1469362. Epub 2018 Jul 26.
Root border cells lie at the interface between the root cap and the soil, secreting mucilage containing polysaccharides and molecules influencing microbial growth around the root. Border cells are sloughed off from the root surface, and the detachment is associated with secretion of xylogalacturonan (XGA). Recently, we showed that in alfalfa XGA secretion is mediated by large vesicles arising from the trans-Golgi in root cap cells. These vesicles are detected in precursor cells of border cells, but their fusion with the plasma membrane is observed only in border cells. We have now examined XGA secretion from maize border cells and Arabidopsis border-like cells using transmission electron microscopy and immunolabeling. In the root caps of both species, XGA is packaged into vesicles derived from the trans-Golgi, not in the vesicles from the trans-Golgi network as in the alfalfa root cap. Border cell-specific exocytosis of XGA was observed in the maize root suggesting that sorting and secretion of XGA in the root cap are conserved in monocot plants.
根边缘细胞位于根冠与土壤的界面处，分泌含有多糖和影响根周围微生物生长的分子的黏液。边缘细胞从根表面脱落，这种脱落与木糖半乳糖醛酸聚糖（XGA）的分泌有关。最近，我们发现苜蓿中XGA的分泌是由根冠细胞中反式高尔基体产生的大囊泡介导的。这些囊泡在边缘细胞的前体细胞中被检测到，但它们与质膜的融合仅在边缘细胞中观察到。我们现在使用透射电子显微镜和免疫标记检查了玉米边缘细胞和拟南芥类边缘细胞中XGA的分泌。在这两个物种的根冠中，XGA被包装到源自反式高尔基体的囊泡中，而不像苜蓿根冠那样包装到反式高尔基体网络的囊泡中。在玉米根中观察到XGA的边缘细胞特异性胞吐作用，这表明根冠中XGA的分选和分泌在单子叶植物中是保守的。
