Hohl I, Robinson D G, Chrispeels M J, Hinz G
Pflanzenphysiologisches Institut, Universität Göttingen, Germany.
J Cell Sci. 1996 Oct;109 ( Pt 10):2539-50. doi: 10.1242/jcs.109.10.2539.
Storage parenchyma cells of developing legume cotyledons actively transport large amounts of storage proteins to protein storage vacuoles (PSV). These proteins are synthesized on the endoplasmic reticulum and pass through the Golgi apparatus. Clathrin coated vesicles (CCV) and small electron dense vesicles found near the trans-Golgi network (TGN) have both been implicated in the Golgi-to-vacuole transport step. Recent findings that protein storage cells contain more than one type of vacuole have necessitated a re-examination of the role of both types of vesicles in vacuolar protein transport. Immunoblots of highly purified CCV preparations and immunogold labelling with antibodies to the storage proteins vicilin and legumin, indicate that the dense vesicles, but not the CCV, are involved in storage protein transport in pea cotyledons. This result is supported by the finding that alpha-TIP, a protein characteristic of the PSV membrane, is absent from CCV. In addition, complex glycoproteins appear to be carried by CCV but are not detectable in the PSV. We suggest on the basis of these data that storage proteins and other vacuolar proteins such as acid hydrolases are not sorted by the same mechanism and are transported by different types of vesicles to different types of vacuoles.
发育中的豆科植物子叶的贮藏薄壁细胞会将大量贮藏蛋白主动运输到蛋白贮藏液泡（PSV）中。这些蛋白质在内质网上合成，然后经过高尔基体。网格蛋白包被囊泡（CCV）以及在反式高尔基体网络（TGN）附近发现的小电子致密囊泡都与从高尔基体到液泡的运输步骤有关。最近的研究发现，蛋白贮藏细胞含有不止一种类型的液泡，这就需要重新审视这两种囊泡在液泡蛋白运输中的作用。对高度纯化的CCV制剂进行免疫印迹分析，并用针对贮藏蛋白豌豆球蛋白和豆球蛋白的抗体进行免疫金标记，结果表明，致密囊泡而非CCV参与了豌豆子叶中贮藏蛋白的运输。这一结果得到了以下发现的支持：CCV中不存在PSV膜特有的蛋白质α-TIP。此外，复合糖蛋白似乎由CCV携带，但在PSV中无法检测到。基于这些数据，我们认为贮藏蛋白和其他液泡蛋白（如酸性水解酶）的分选机制不同，并且由不同类型的囊泡运输到不同类型的液泡中。
