Symplasmic fields in the tunica of the shoot apical meristem coordinate morphogenetic events.
Symplasmic fields in the tunica of the shoot apical meristem coordinate morphogenetic events.
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作者：
P. Rinne;C. Schoot
在植物中，复杂的细胞相互作用需要形态发生信号的交换，是地上部顶端分生组织形态发生的基础。由于所有的顶端分生组织细胞都通过胞间连丝相互连接，我们研究了是否存在共质途径，这些途径可能优先输送顶端分生组织中的代谢物和潜在的形态原，以及它们是否支持确定的附属物的形成和未分化中心的维持。用荧光染料对白桦幼苗顶端分生组织的细胞膜透性进行了研究，结果表明，白桦幼苗顶端分生组织的顶端分生组织的细胞膜。被共质划分为两个同心场，这限制了小潜在形态原的共质扩散到其边界内的细胞。这两个场之间的瞬时连接是在塑形计时器的早期建立的，增强了共质扩散的信号分子的径向交换。我们认为，细胞膜的共质分裂提供了一种方法，将细胞联合成通讯间隔，调用它们之间的边界相互作用，并保护远端分生组织细胞不受器官发生的影响。电生理测量表明，此外，这些领域的细胞组成代谢工作单位。这些共质场与形态发生的相关性是通过短光周期处理来建立的，短光周期导致这些场分解成共质体孤立的细胞。单宁酸染色和原位免疫定位显示，细胞隔离是由于括约肌固有的葡聚糖合成酶复合体的激活。结果是，所有的胞间连丝上都形成了团块，导致形态发生失活。
In plants, complex cellular interactions, which require the exchange of morphogenetic signals, underlie morphogenesis at the shoot apical meristem. Since all apical meristem cells are interconnected by plasmodesmata, we have investigated if symplasmic paths are available which may preferentially channel metabolites and potential morphogens in the apical meristem, and whether they could support both the formation of determinate appendages and the sustainment of an undifferentiated centre. Experiments in which the permeability of the symplasm was probed with fluorescent dye revealed that the tunica of the apical meristem of birch seedlings (Betula pubescence Ehrh.) is symplasmically compartmentalized into two concentric fields, which restrict the symplasmic diffusion of small potential morphogens to the cells inside their boundaries. A transient connection between the two fields was established early in a plastochron, potentiating the radial exchange of symplasmically diffusing signalling molecules. We suggest that the symplasmic subdivision of the tunica offers a means to unite cells into communication compartments, invoke boundary interactions between them, and shield the distal meristem cells from organogenesis. Electrophysiological measurements indicate that, in addition, the cells of these fields constitute metabolic working units. The relevance of these symplasmic fields for morphogenesis was established experimentally by treatment with short photoperiod, which induced breakdown of the fields into symplasmically isolated cells. Tannic acid staining and in situ immunolocalisation revealed that cell isolation was due to the activation of glucan synthase complexes intrinsic to sphincters. As a result callose plugs were formed on all plasmodesmata leading to morphogenetic deactivation.