Sec22 and Memb11 Are v-SNAREs of the Anterograde Endoplasmic Reticulum-Golgi Pathway in Tobacco Leaf Epidermal Cells

Abstract

Distinct sets of soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptors (SNAREs) are distributed to specific intracellular compartments and catalyze membrane fusion events. Although the central role of these proteins in membrane fusion is established in nonplant systems, little is known about their role in the early secretory pathway of plant cells. Analysis of the Arabidopsis (Arabidopsis thaliana) genome reveals 54 genes encoding SNARE proteins, some of which are expected to be key regulators of membrane trafficking between the endoplasmic reticulum (ER) and the Golgi. To gain insights on the role of SNAREs of the early secretory pathway in plant cells, we have cloned the Arabidopsis v-SNAREs Sec22, Memb11, Bet11, and the t-SNARE Sed5, and analyzed their distribution in plant cells in vivo. By means of live cell imaging, we have determined that these SNAREs localize at the Golgi apparatus. In addition, Sec22 was also distributed at the ER. We have then focused on understanding the function of Sec22 and Memb11 in comparison to the other SNAREs. Overexpression of the v-SNAREs Sec22 and Memb11 but not of the other SNAREs induced collapse of Golgi membrane proteins into the ER, and the secretion of a soluble secretory marker was abrogated by all SNAREs. Our studies suggest that Sec22 and Memb11 are involved in anterograde protein trafficking at the ER-Golgi interface.

Overexpression of theArabidopsisSyntaxin PEP12/SYP21 Inhibits Transport from the Prevacuolar Compartment to the Lytic Vacuole in Vivo

“…This protein was identified as a multicopy suppressor of an ERD2 mutant (Hardwick et al, 1992) and found to cause a general reduction in anterograde ER-to-Golgi traffic, thus compensating for the ERD2 defect. Similar inhibitory effects were observed for the overexpressed full-length Golgi SNAREs Bos1 and Sec22 in tobacco epidermis cells (Chatre et al, 2005).…”

SNARE-Ware: The Role of SNARE-Domain Proteins in Plant Biology

“…These studies revealed that most SNAREs are associated with specific intracellular compartments, whereas some localize to two or more distinct organelles, possibly owing to shuttling between subcellular compartments. Despite the inherent caveats typically associated with cauliflower mosaic virus 35S promoter-driven mis-/overexpression, these and similar experiments by other groups (e.g., Chatre et al 2005, Latijnhouwers et al 2005, Takeuchi et al 2002 suggest at least preferential association of individual SNARE proteins with particular organelles. Likewise, overexpression of full-size SNAREs or cytoplasmic SNARE domains has provided insights into the potential role of these isoforms in subcellular vesicle trafficking (e.g., Chatre et al 2005, Foresti et al 2006, Geelen et al 2002, Sutter et al 2006b).…”

Caesium accumulation in yeast and plants is selectively repressed by loss of the SNARE Sec22p/SEC22

“…S2b). It has been characterized as a SNARE involved in the anterograde vesicle traffic at the ER to Golgi interface 25 . In contrast to its S. cerevisiae ortholog, A. thaliana SEC22 is essential, as it is required for gametophyte development 18 .…”