Loss of GET pathway orthologs in Arabidopsis thaliana causes root hair growth defects and affects SNARE abundance
Loss of GET pathway orthologs in Arabidopsis thaliana causes root hair growth defects and affects SNARE abundance
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DOI：
10.1073/pnas.1619525114
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发表时间：
2017-01
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通讯作者：
S. Xing;D. Mehlhorn;Niklas Wallmeroth;L. Asseck;Ritwika Kar;A. Voß;P. Denninger;V. A. Schmidt;M. Schwarzländer;Y. Stierhof;G. Grossmann;Christopher Grefen
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作者：
S. Xing;D. Mehlhorn;Niklas Wallmeroth;L. Asseck;Ritwika Kar;A. Voß;P. Denninger;V. A. Schmidt;M. Schwarzländer;Y. Stierhof;G. Grossmann;Christopher Grefen
根毛是根皮层的单细胞延伸，提供锚定和增加表面积的营养和水分吸收。它们的快速，尖端集中的生长展示了根毛作为一个很好的遗传模型来研究细胞水平上的生理和发育过程。我们发现了一种根毛表型，它依赖于尾锚定（TA）蛋白（GET）途径的引导进入的推定拟南芥直向同源物，该途径有助于TA蛋白在酵母和哺乳动物中的膜插入。我们发现，植物已经进化出多个旁系同源的特定GET途径的组成部分，虽然在一个特定的方式。此外，我们表明，差异表达的途径组件导致多效性的生长缺陷，建议替代途径TA插入和其他功能的GET在植物中。可溶性N-乙基马来酰亚胺敏感因子附着蛋白受体（SNARE）蛋白是细胞运输的关键参与者，并协调重要的细胞过程，如胞质分裂、病原体防御和离子转运调节。除了少数例外，SNARE是尾锚定（TA）蛋白，具有对其膜整合至关重要的C-末端疏水结构域。最近，在哺乳动物和酵母细胞中描述了尾锚定蛋白的引导进入（GET）途径，其用作TA蛋白插入的蓝图[Schuldiner M等人（2008）Cell 134（4）：634-645; Stefanovic S，Hegde RS（2007）Cell 128（6）：1147-1159]。该途径由六种蛋白质组成，其中胞质ATP酶GET 3将新合成的TA蛋白质从核糖体后送至内质网（ER）膜。结构和生物化学的见解证实了途径组分促进膜插入的潜力，但在多细胞生物中的生理意义仍有待解决。我们对来自18个不同物种的37个GET 3直系同源物的系统发育分析显示存在两个不同的GET 3进化枝。我们鉴定并分析了拟南芥中的GET途径组分，发现Atget系中根毛伸长减少，这可能是SNARE生物合成减少的结果。AtGET 3a在受体敲除（KO）中的过表达导致严重的生长缺陷，这表明存在替代插入途径，同时突出GET途径在植物细胞内稳态中的复杂参与。
Significance Root hairs are unicellular extensions of the rhizodermis, providing anchorage and an increase in surface area for nutrient and water uptake. Their fast, tip-focused growth showcases root hairs as an excellent genetic model to study physiological and developmental processes on the cellular level. We uncovered a root hair phenotype that is dependent on putative Arabidopsis orthologs of the Guided Entry of Tail-anchored (TA) proteins (GET) pathway, which facilitates membrane insertion of TA proteins in yeast and mammals. We found that plants have evolved multiple paralogs of specific GET pathway components, albeit in a compartment-specific manner. In addition, we show that differential expression of pathway components causes pleiotropic growth defects, suggesting alternative pathways for TA insertion and additional functions of GET in plants. Soluble N-ethylmaleimide–sensitive factor attachment protein receptor (SNARE) proteins are key players in cellular trafficking and coordinate vital cellular processes, such as cytokinesis, pathogen defense, and ion transport regulation. With few exceptions, SNAREs are tail-anchored (TA) proteins, bearing a C-terminal hydrophobic domain that is essential for their membrane integration. Recently, the Guided Entry of Tail-anchored proteins (GET) pathway was described in mammalian and yeast cells that serve as a blueprint of TA protein insertion [Schuldiner M, et al. (2008) Cell 134(4):634–645; Stefanovic S, Hegde RS (2007) Cell 128(6):1147–1159]. This pathway consists of six proteins, with the cytosolic ATPase GET3 chaperoning the newly synthesized TA protein posttranslationally from the ribosome to the endoplasmic reticulum (ER) membrane. Structural and biochemical insights confirmed the potential of pathway components to facilitate membrane insertion, but the physiological significance in multicellular organisms remains to be resolved. Our phylogenetic analysis of 37 GET3 orthologs from 18 different species revealed the presence of two different GET3 clades. We identified and analyzed GET pathway components in Arabidopsis thaliana and found reduced root hair elongation in Atget lines, possibly as a result of reduced SNARE biogenesis. Overexpression of AtGET3a in a receptor knockout (KO) results in severe growth defects, suggesting presence of alternative insertion pathways while highlighting an intricate involvement for the GET pathway in cellular homeostasis of plants.