Department of Botany, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
Dev Biol. 2011 Apr 1;352(1):48-57. doi: 10.1016/j.ydbio.2011.01.014. Epub 2011 Jan 21.
Large vacuoles are characteristic of plant and fungal cells, and their origin has long attracted interest. The cellular slime mould provides a unique opportunity to study the de novo formation of vacuoles because, in its life cycle, a subset of the highly motile animal-like cells (prestalk cells) rapidly develops a single large vacuole and cellulosic cell wall to become plant-like cells (stalk cells). Here we describe the origin and process of vacuole formation using live-imaging of Dictyostelium cells expressing GFP-tagged ammonium transporter A (AmtA-GFP), which was found to reside on the membrane of stalk-cell vacuoles. We show that stalk-cell vacuoles originate from acidic vesicles and autophagosomes, which fuse to form autolysosomes. Their repeated fusion and expansion accompanied by concomitant cell wall formation enable the stalk cells to rapidly develop turgor pressure necessary to make the rigid stalk to hold the spores aloft. Contractile vacuoles, which are rich in H(+)-ATPase as in plant vacuoles, remained separate from these vacuoles. We further argue that AmtA may play an important role in the control of stalk-cell differentiation by modulating the pH of autolysosomes.
大液泡是植物和真菌细胞的特征，其起源一直引起人们的兴趣。细胞黏菌为研究液泡的从头形成提供了一个独特的机会，因为在其生命周期中，一组高度能动的类似动物的细胞（前柄细胞）迅速形成一个大液泡和纤维素细胞壁，成为类似植物的细胞（柄细胞）。在这里，我们使用活体成像描述了液泡的形成过程，展示了 GFP 标记的铵转运蛋白 A（AmtA-GFP）在表达 Dictyostelium 细胞中的位置，该蛋白位于柄细胞液泡的膜上。我们发现柄细胞液泡起源于酸性囊泡和自噬体，它们融合形成自溶体。自溶体的反复融合和扩张伴随着细胞壁的形成，使柄细胞能够迅速产生膨压，以形成坚硬的柄，将孢子举到高处。富含 H(+)-ATPase 的收缩液泡与这些液泡分离。我们进一步认为，AmtA 可能通过调节自溶体的 pH 值，在柄细胞分化的控制中发挥重要作用。
