COPII Sec23 proteins form isoform-specific endoplasmic reticulum exit sites with differential effects on polarized growth
COPII Sec23 proteins form isoform-specific endoplasmic reticulum exit sites with differential effects on polarized growth
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DOI：
10.1093/plcell/koab229
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发表时间：
2021-09-17
期刊：
影响因子：
11.6
通讯作者：
Bezanilla, Magdalena
中科院分区：
文献类型：
--
作者：
Chang, Mingqin;Wu, Shu-Zon;Bezanilla, Magdalena
外壳蛋白复合物II （COPII）是一种在内质网（ER）上形成囊泡的外壳蛋白复合物，介导向高尔基体的运输。虽然后生动物很少有基因编码每个COPII成分，但植物已经扩展了这些基因家族，导致植物COPII功能多样化的假设。在藓类Physcomitrium (Physcomitrella) patens中，Sec23/24基因家族各由7个基因组成。沉默Sec23/24揭示了对极化生长的异构体特异性贡献，而密切相关的Sec23D/E和Sec24C/D对原体细胞发育至关重要。重点研究Sec23，我们发现Sec23D/E介导ER到高尔基体的运输，并且对尖端生长至关重要，Sec23D定位于假定的ER出口位点。相比之下，Sec23A、B、C、F和G是可有可无的，并不定量地影响ER-to-Golgi贩运。然而，Delta sec23abcfg植物的质膜货物分泌减少。在四个高表达的原Sec23基因中，Sec23F/G是陆地植物中特别保留的Sec23分支的分支成员。值得注意的是，Sec23G聚集在er相关的病灶上，这些病灶明显更大，不与Sec23D重叠，并且独立于Sec23D。虽然Sec23D/E形成ER出口位点，并作为尖端生长原体必需的真正的COPII组分发挥作用，但Sec23G和密切相关的Sec23F可能在功能上多样化，形成独立的ER出口位点，并参与高尔基非依赖性转运途径。
Coat Protein complex II (COPII), a coat protein complex that forms vesicles on the endoplasmic reticulum (ER), mediates trafficking to the Golgi. While metazoans have few genes encoding each COPII component, plants have expanded these gene families, leading to the hypothesis that plant COPII has functionally diversified. In the moss Physcomitrium (Physcomitrella) patens, the Sec23/24 gene families are each composed of seven genes. Silencing Sec23/24 revealed isoform-specific contributions to polarized growth, with the closely related Sec23D/E and Sec24C/D essential for protonemal development. Focusing on Sec23, we discovered that Sec23D/E mediate ER-to Golgi transport and are essential for tip growth, with Sec23D localizing to presumptive ER exit sites. In contrast, Sec23A, B, C, F, and G are dispensable and do not quantitatively affect ER-to-Golgi trafficking. However, Delta sec23abcfg plants exhibited reduced secretion of plasma membrane cargo. Of the four highly expressed protonemal Sec23 genes, Sec23F/G are members of a divergent Sec23 clade specifically retained in land plants. Notably, Sec23G accumulates on ER-associated foci that are significantly larger, do not overlap with, and are independent of Sec23D. While Sec23D/E form ER exit sites and function as bona fide COPII components essential for tip-growing protonemata, Sec23G and the closely related Sec23F have likely functionally diversified, forming separate and independent ER exit sites and participating in Golgi-independent trafficking pathways.