Secretory cargos are collected at endoplasmic reticulum (ER) exit sites (ERES) before transport to the Golgi apparatus. Decades of research have provided many details of the molecular events underlying ER-Golgi exchanges. Essential questions, however, remain about the organization of the ER-Golgi interface in cells and the type of membrane structures mediating traffic from ERES. To investigate these, we use transgenic tagging in Drosophila flies, 3D-structured illumination microscopy (SIM), and focused ion beam scanning electron microscopy (FIB-SEM) to characterize ERES-Golgi units in collagen-producing fat body, imaginal discs, and imaginal discs overexpressing ERES determinant Tango1. Facing ERES, we find a pre-cis-Golgi region, equivalent to the vertebrate ER-Golgi intermediate compartment (ERGIC), involved in both anterograde and retrograde transport. This pre-cis-Golgi is continuous with the rest of the Golgi, not a separate compartment or collection of large carriers, for which we find no evidence. We observe, however, many vesicles, as well as pearled tubules connecting ERES and Golgi.

在运输到高尔基体之前，在内质网 (ER) 出口部位 (ERES) 收集分泌物。数十年的研究提供了许多关于 ER-高尔基体交换的分子事件的细节。然而，基本问题仍然是关于细胞中 ER-高尔基界面的组织以及介导 ERES 流量的膜结构类型。为了研究这些，我们在果蝇中使用转基因标记、3D 结构照明显微镜 (SIM) 和聚焦离子束扫描电子显微镜 (FIB-SEM) 来表征产生胶原蛋白的脂肪体、成像盘和过度表达 ERES 行列式 Tango1 的成像盘。面对 ERES，我们找到了一个精确的-Golgi 区域，相当于脊椎动物 ER-Golgi 中间隔室 (ERGIC)，参与顺行和逆行运输。这个精确的高尔基体与高尔基体的其余部分是连续的，而不是一个单独的隔间或大型载体的集合，我们找不到任何证据。然而，我们观察到许多囊泡，以及连接 ERES 和高尔基体的珠状小管。