Developmentally distinct activities of the exocyst enable rapid cell elongation and determine meristem size during primary root growth in Arabidopsis
Developmentally distinct activities of the exocyst enable rapid cell elongation and determine meristem size during primary root growth in Arabidopsis
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DOI：
10.1186/s12870-014-0386-0
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发表时间：
2014-12-31
影响因子：
5.3
通讯作者：
Fowler, John E.
中科院分区：
文献类型：
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作者：
Cole, Rex A.;McInally, Samantha A.;Fowler, John E.
背景：胞吐作用是根生长不可或缺的：控制生长的系统的运输组分（例如，PIN生长素运输蛋白质）到质膜，并分泌使细胞壁扩展到质外体的物质。真核生物中胞吐的时空调节通常涉及胞吐，这是一种八聚体复合物，其将选定的分泌囊泡拴系到质膜上的特定位点并促进其胞吐。本研究以拟南芥为材料，研究了外囊突变体（SEC 5、SEC 8、EXO 70 A1和EXO 84 B）在主根生长中的作用。即使在最严重的缺陷线，在根尖的静止中心和组织层的组织似乎类似于野生型，虽然分生组织，过渡和伸长区较短。在突变体中细胞生产率降低是由于较短的分生组织，而不是延长细胞周期。此外，突变体在伸长区而不是分生区表现出减少的各向异性细胞扩增，导致形状与野生型相似的较短的成熟细胞。正如预期的那样，对布雷菲德菌素A的超敏反应将突变体根生长缺陷与改变的囊泡运输联系起来。几种实验方法（例如，剂量-反应测量，定位的信号组件）未能确定异常的生长素或油菜素类固醇信号作为一个主要的驱动程序减少根生长exocyst mutants.Conclusions：外囊参与两个空间上不同的发展过程，显然是由机制不直接联系到生长素或油菜素类固醇信号通路，以帮助建立根分生组织的大小，并促进细胞快速扩张的伸长区。
Background: Exocytosis is integral to root growth: trafficking components of systems that control growth (e.g., PIN auxin transport proteins) to the plasma membrane, and secreting materials that expand the cell wall to the apoplast. Spatiotemporal regulation of exocytosis in eukaryotes often involves the exocyst, an octameric complex that tethers selected secretory vesicles to specific sites on the plasma membrane and facilitates their exocytosis. We evaluated Arabidopsis lines with mutations in four exocyst components (SEC5, SEC8, EXO70A1 and EXO84B) to explore exocyst function in primary root growth.Results: The mutants have root growth rates that are 82% to 11% of wild-type. Even in lines with the most severe defects, the organization of the quiescent center and tissue layers at the root tips appears similar to wild-type, although meristematic, transition, and elongation zones are shorter. Reduced cell production rates in the mutants are due to the shorter meristems, but not to lengthened cell cycles. Additionally, mutants demonstrate reduced anisotropic cell expansion in the elongation zone, but not the meristematic zone, resulting in shorter mature cells that are similar in shape to wild-type. As expected, hypersensitivity to brefeldin A links the mutant root growth defect to altered vesicular trafficking. Several experimental approaches (e.g., dose-response measurements, localization of signaling components) failed to identify aberrant auxin or brassinosteroid signaling as a primary driver for reduced root growth in exocyst mutants.Conclusions: The exocyst participates in two spatially distinct developmental processes, apparently by mechanisms not directly linked to auxin or brassinosteroid signaling pathways, to help establish root meristem size, and to facilitate rapid cell expansion in the elongation zone.