Functional diversification of Arabidopsis SEC1-related SM proteins in cytokinetic and secretory membrane fusion
Functional diversification of Arabidopsis SEC1-related SM proteins in cytokinetic and secretory membrane fusion
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DOI：
10.1073/pnas.1722611115
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发表时间：
2018-06-12
影响因子：
11.1
通讯作者：
Juergens, Gerd
中科院分区：
文献类型：
--
作者：
Karnahl, Matthias;Park, Misoon;Juergens, Gerd
Sec1/Munc18 (SM) 蛋白通过与 Qa-SNARE 或新生的 trans-SNARE 复合物相互作用来促进膜融合。裸子植物和基部被子植物 Amborella 仅有一个 SEC1 基因，与拟南芥中的 KEULE 基因相关。 However, the genomes of most angiosperms including Arabidopsis encode three SEC1-related SM proteins of which only KEULE has been functionally characterized as interacting with the cytokinesisspecific Qa-SNARE KNOLLE during cell-plate formation.在这里，我们分析了 KEULE 最接近的旁系同源物 SEC1B。与 keule 突变体的胞质分裂缺陷相反，sec1b 突变体是纯合的。然而，keule sec1b 双突变体几乎是配子体致死的，表现出塌陷的花粉粒，这表明 SEC1B 和 KEULE 在分泌依赖性生长中的功能存在大量重叠。 SEC1B 强烈倾向于与参与分泌和胞质分裂的进化古老的 Qa-SNARE SYP132 相互作用，而 KEULE 与 KNOLLE 和 SYP132 相互作用。这种与 Qa-SNARE 的不同相互作用可能是由两种 SM 蛋白的结构域 1 和 2a 赋予的。对相关 SEC1 Qa-SNARE 双突变体的所有四种可能组合的比较分析表明，在胞质分裂中，SEC1B 与 KNOLLE 的相互作用不起作用，而 KEULE 与 KNOLLE 的相互作用很普遍，并且在功能上与 SEC1B 和 KEU 与 SYP132 的相互作用一样重要。我们的结果表明，在被子植物进化过程中，两种 SEC1 相关 SM 蛋白的功能多样化导致 SEC1B 与 Qa-SNARE SYP132 的相互作用增强，因此 SEC1B 在分泌中发挥主导作用。
Sec1/Munc18 (SM) proteins contribute to membrane fusion by interacting with Qa-SNAREs or nascent trans-SNARE complexes. Gymnosperms and the basal angiosperm Amborella have only a single SEC1 gene related to the KEULE gene in Arabidopsis. However, the genomes of most angiosperms including Arabidopsis encode three SEC1-related SM proteins of which only KEULE has been functionally characterized as interacting with the cytokinesisspecific Qa-SNARE KNOLLE during cell-plate formation. Here we analyze the closest paralog of KEULE named SEC1B. In contrast to the cytokinesis defects of keule mutants, sec1b mutants are homozygous viable. However, the keule sec1b double mutant was nearly gametophytically lethal, displaying collapsed pollen grains, which suggests substantial overlap between SEC1B and KEULE functions in secretion-dependent growth. SEC1B had a strong preference for interaction with the evolutionarily ancient Qa-SNARE SYP132 involved in secretion and cytokinesis, whereas KEULE interacted with both KNOLLE and SYP132. This differential interaction with Qa-SNAREs is likely conferred by domains 1 and 2a of the two SM proteins. Comparative analysis of all four possible combinations of the relevant SEC1 Qa-SNARE double mutants revealed that in cytokinesis, the interaction of SEC1B with KNOLLE plays no role, whereas the interaction of KEULE with KNOLLE is prevalent and functionally as important as the interactions of both SEC1B and KEU with SYP132 together. Our results suggest that functional diversification of the two SEC1-related SM proteins during angiosperm evolution resulted in enhanced interaction of SEC1B with Qa-SNARE SYP132, and thus a predominant role of SEC1B in secretion.