VAMP721a and VAMP721d are important for pectin dynamics and release of bacteria in soybean nodules
VAMP721a and VAMP721d are important for pectin dynamics and release of bacteria in soybean nodules
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DOI：
10.1111/nph.13837
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发表时间：
2016-05-01
期刊：
影响因子：
9.4
通讯作者：
Fedorova, Elena E.
中科院分区：
文献类型：
--
作者：
Gavrin, Aleksandr;Chiasson, David;Fedorova, Elena E.
在根瘤中，根瘤菌通过侵染线进入宿主细胞。细菌从感染线的无细胞壁区域释放到宿主细胞是可能的。我们推测VAMP721d和VAMP721e的胞吐途径可能在根瘤菌释放过程中对细胞壁的局部修饰起作用。为了阐明VAMP721d和VAMP721e的作用，我们使用了大豆，这是一种具有确定类型的根瘤的植物。分析了GmVAMP721d部分沉默的对照和根瘤中初生细胞壁的主要多糖化合物的定位。GmVAMP721d的沉默抑制了根瘤菌的释放。被感染的细胞不是含有根瘤菌的膜隔间--共生体--而是嵌在甲酯化和去甲酯化果胶基质中的大群细菌。这些星团被一层膜包围着。我们发现GmVAMP721d阳性囊泡不运输甲酯化果胶。我们推测，它们可能会传递与果胶周转有关的酶。随后，我们发现GmVAMP721d与果胶裂解酶部分共定位。因此，VAMP721d的生物学作用可能是通过将果胶修饰酶运送到释放部位来解释的。
In root nodules rhizobia enter host cells via infection threads. The release of bacteria to a host cell is possible from cell wall-free regions of the infection thread. We hypothesized that the VAMP721d and VAMP721e exocytotic pathway, identified before in Medicago truncatula, has a role in the local modification of cell wall during the release of rhizobia. To clarify the role of VAMP721d and VAMP721e we used Glycine max, a plant with a determinate type of nodule. The localization of the main polysaccharide compounds of primary cell walls was analysed in control vs nodules with partially silenced GmVAMP721d. The silencing of GmVAMP721d blocked the release of rhizobia. Instead of rhizobia-containing membrane compartments - symbiosomes - the infected cells contained big clusters of bacteria embedded in a matrix of methyl-esterified and de-methyl-esterified pectin. These clusters were surrounded by a membrane. We found that GmVAMP721d-positive vesicles were not transporting methyl-esterified pectin. We hypothesized that they may deliver the enzymes involved in pectin turnover. Subsequently, we found that GmVAMP721d is partly co-localized with pectate lyase. Therefore, the biological role of VAMP721d may be explained by its action in delivering pectin-modifying enzymes to the site of release.