Overexpressed Tomosyn Binds Syntaxins and Blocks Secretion during Pollen Development
Overexpressed Tomosyn Binds Syntaxins and Blocks Secretion during Pollen Development
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过度表达的 Tomosyn 会在花粉发育过程中结合突触蛋白并阻止分泌。
DOI：
10.1104/pp.19.00965
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发表时间：
2019-11-01
期刊：
影响因子：
7.4
通讯作者：
Bao, Yiqun
中科院分区：
文献类型：
--
作者：
Li, Bingxuan;Li, Yanbin;Bao, Yiqun
SNARE（可溶性n -乙基马来酰亚胺敏感因子附着蛋白受体）复合物的形成是细胞膜内融合所必需的，因此在分泌等过程中起关键作用。然而，我们对与Qa-SNAREs结合的调控因子知之甚少，这些因子在植物中也被称为syntaxins （SYPs）。在这里，我们对拟南芥（Arabidopsis thaliana） Tomosyn蛋白（AtTMS）进行了表征，并证明它是植物中SYPs的保守调节因子。AtTMS通过其含有R-SNARE基序的C端与花粉表达的pm常驻SYP1s （SYP111、SYP124、SYP125、SYP131和SYP132）的Qa结构域紧密结合，这些SYP1s从12个syp中筛选出来。从双细胞阶段开始，AtTMS在花粉中高表达，在UBIQUITIN10、MSP1或LAT52启动子的控制下，AtTMS过表达都会导致小孢子期后花粉缺陷，抑制花粉分泌，导致花粉有丝分裂过程中内质沉积和细胞板形成失败。在烟草叶表皮细胞中，AtTMS过表达抑制分泌的GFP的分泌。缺陷被mccherry标记的SYP124， SYP125, SYP131，或SYP132拯救。在体内，SYP132部分挽救了pMSP1:AtTMS表型。此外，缺乏跨膜结构域的AtTMS被SYP124、SYP125、SYP131和SYP132募集到质膜上，并与囊泡相关膜蛋白721/722竞争，与SYP132等结合。总之，我们的研究结果表明，AtTMS可能是花粉分泌的负调节因子，在花粉发育过程中，主动分泌可能被微调。
SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptors) complex formation is necessary for intracellular membrane fusion and thus has a key role in processes such as secretion. However, little is known about the regulatory factors that bind to Qa-SNAREs, which are also known as syntaxins (SYPs) in plants. Here, we characterized Arabidopsis (Arabidopsis thaliana) Tomosyn protein (AtTMS) and demonstrated that it is a conserved regulator of SYPs in plants. AtTMS binds strongly via its R-SNARE motif-containing C terminus to the Qa domain of PM-resident, pollen-expressed SYP1s (SYP111, SYP124, SYP125, SYP131, and SYP132), which were narrowed down from 12 SYPs. AtTMS is highly expressed in pollen from the bicellular stage onwards, and overexpression of AtTMS under the control of the UBIQUITIN10, MSP1, or LAT52 promoter all resulted in defective pollen after the microspore stage in which secretion was inhibited, leading to the failure of intine deposition and cell plate formation during pollen mitosis I. In tobacco (Nicotiana benthamiana) leaf epidermal cells, overexpression of AtTMS inhibited the secretion of secreted GFP. The defects were rescued by mCherry-tagged SYP124, SYP125, SYP131, or SYP132. In vivo, SYP132 partially rescued the pMSP1:AtTMS phenotype. In addition, AtTMS, lacking a transmembrane domain, was recruited to the plasma membrane by SYP124, SYP125, SYP131, and SYP132 and competed with Vesicle-Associated Membrane Protein721/722 for binding to, for example, SYP132. Together, our results demonstrated that AtTMS might serve as a negative regulator of secretion, whereby active secretion might be fine-tuned during pollen development.