n nnnRhizobium bacteria form N2-fixing organelles, called symbiosomes,inside the cells of legume root nodules. The bacteria are generallythought to enter the cells via an endocytosis-like process.To examine this, we studied the identity of symbiosomes in relationto the endocytic pathway. We show that in Medicago truncatula,the small GTPases Rab5 and Rab7 are endosomal membrane identitymarkers, marking different (partly overlapping) endosome populations.Although symbiosome formation is considered to be an endocytosis-likeprocess, symbiosomes do not acquire Rab5 at any stage duringtheir development, nor do they accept the trans-Golgi networkidentity marker SYP4, presumed to mark early endosomes in plants.By contrast, the endosomal marker Rab7 does occur on symbiosomesfrom an early stage of development when they have stopped dividingup to the senescence stage. However, the symbiosomes do notacquire vacuolar SNAREs (SYP22 and VTI11) until the onset oftheir senescence. By contrast, symbiosomes acquire the plasmamembrane SNARE SYP132 from the start of symbiosome formationthroughout their development. Therefore, symbiosomes appearto be locked in a unique SYP132- and Rab7-positive endosomestage and the delay in acquiring (lytic) vacuolar identity (e.g.,vacuolar SNAREs) most likely ensures their survival and maintenanceas individual units.展开▼
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n TOP n <字体颜色= 464c53>抽象 n 介绍 n 结果 n 讨论 n 方法 n 参考文献 n n nnn 根瘤菌细菌形成N 2 固定细胞器，称为共生体mes， 在豆类根瘤的细胞内部。通常认为细菌是通过内吞作用样过程进入细胞的。 为了对此进行研究，我们研究了与 相关的共生体的身份。内吞途径。我们显示，在 run藜， 中，小的GTPases Rab5和Rab7是内体膜身份标记，标记了不同的（部分重叠）内体群体。 SUP> 尽管共生体的形成被认为是内吞作用样的 过程，但共生体在 的发育过程中的任何阶段都没有获得Rab5，也没有接受Rab5。反式高尔基网 同一性标记SYP4，被认为可标记植物中的早期内体。 相反，内体标记Rab7确实存在于共生体 上他们已经停止将 划分为衰老阶段的早期阶段。但是，共生体直到 衰老才开始获得液泡SNARE（SYP22和VTI11）。相比之下，共生体从形成共生体 开始就获得了血浆 膜SNARE SYP132。因此，共生体似乎被 锁定在独特的SYP132-和Rab7阳性内体 阶段，并且延迟了获得（裂解）液泡身份（例如， vacular SNAREs）最有可能确保它们作为单个单元的生存和维持。 。
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Laboratory of Molecular Biology, Graduate School of Experimental Plant Sciences, Wageningen University, 6708 PB Wageningen, The Netherlands;
Laboratory of Molecular Biology, Graduate School of Experimental Plant Sciences, Wageningen University, 6708 PB Wageningen, The Netherlands|K.A. Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Moscow 127392, Russia;
Laboratory of Molecular Biology, Graduate School of Experimental Plant Sciences, Wageningen University, 6708 PB Wageningen, The Netherlands;
Laboratory of Molecular Biology, Graduate School of Experimental Plant Sciences, Wageningen University, 6708 PB Wageningen, The Netherlands;
Laboratory of Molecular Biology, Graduate School of Experimental Plant Sciences, Wageningen University, 6708 PB Wageningen, The Netherlands|K.A. Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Moscow 127392, Russia;
Laboratory of Molecular Biology, Graduate School of Experimental Plant Sciences, Wageningen University, 6708 PB Wageningen, The Netherlands;
