Pal Lalita, Belausov Eduard, Dwivedi Vikas, Yechezkel Sela, Sadot Einat
The Institute of Plant Sciences, Department of Ornamental Plants and Agricultural Biotechnology. The Volcani Institute, ARO, Rishon LeZion, Israel.
J Microsc. 2025 Jan;297(1):96-104. doi: 10.1111/jmi.13356. Epub 2024 Aug 30.
The endoplasmic reticulum (ER) is the largest organelle in terms of membrane content, occupying the entire cytoplasmic volume. It is tethered to the cell cortex through ER-plasma membrane contact sites (EPCS). Previous studies have shown that EPCSs labelled by VAP27 align with cortical microtubules, and that ER tubules elongate along microtubules. Here, we addressed the question whether this relationship is bidirectional, with EPCSs influencing microtubule organisation. Using TIRF microscopy to track EPCSs and microtubule dynamics simultaneously, we demonstrate that while EPCSs remain stable, microtubules are highly dynamic and can adjust their positioning based on nearby EPCS in Arabidopsis cotyledon epidermis. In lobes of epidermal cells enclosed by two indentations, where microtubules bundle together, EPCSs flank the bundles and exhibit a distinctive arrangement, forming symmetric arcs in relation to the lobe axis. In guard cells, transversely oriented ER tubules co-align with microtubules. Disrupting microtubules with the drug oryzalin leads to transient guard cells-ER remodelling, followed by its reorganisation into transverse tubules before microtubule recovery. Taken together our observations suggest, that the positioning of EPCSs and cortical microtubules, can affect each other and the organisation of cortical ER.
内质网（ER）就膜含量而言是最大的细胞器，占据整个细胞质体积。它通过内质网-质膜接触位点（EPCS）与细胞皮层相连。先前的研究表明，由VAP27标记的EPCS与皮层微管对齐，并且内质网管沿着微管伸长。在这里，我们探讨了这种关系是否是双向的，即EPCS是否影响微管组织。使用全内反射荧光显微镜（TIRF）同时追踪EPCS和微管动态，我们证明，在拟南芥子叶表皮中，虽然EPCS保持稳定，但微管高度动态，并且可以根据附近的EPCS调整其定位。在由两个凹陷包围的表皮细胞叶中，微管聚集在一起，EPCS位于束的两侧并呈现出独特的排列，相对于叶轴形成对称弧。在保卫细胞中，横向排列的内质网管与微管共对齐。用药物oryzalin破坏微管会导致保卫细胞-内质网的短暂重塑，随后在微管恢复之前重新组织成横向管。综上所述，我们的观察结果表明，EPCS和皮层微管的定位可以相互影响以及皮层内质网的组织。
