SYP71, a Plant-specific Qc-SNARE Protein, Reveals Dual Localization to the Plasma Membrane and the Endoplasmic Reticulum in Arabidopsis

Abstract

ABSTRACT. SNAREs ('Soluble N-ethyl-maleimide sensitive factor attachment protein receptors') play a critical role in the membrane fusion step of the vesicular transport system in eukaryotes. The number of the genes encoding SNARE proteins is estimated to be 64 in Arabidopsis thaliana. This number is much larger than those in other eukaryotes, suggesting a complex membrane trafficking in plants. The Arabidopsis SNAREs, the SYP7 group proteins, SYP71, SYP72, and SYP73, form a plant-specific SNARE subfamily with not-yet-identified functions. We have previously reported that the SYP7 subfamily proteins are predominantly localized to the endoplasmic reticulum in the Arabidopsis suspension cultured cells under transient expression condition. However, several proteomic analyzes indicated the plasma membrane localizations of one of SYP7 subfamily proteins, SYP71. In order to confirm the expression patterns and subcellular localization of SYP7, we performed combination analyses including promoter GUS analysis, a sucrose density gradient centrifugation analysis, as well as an observation on transgenic Arabidopsis plants expressing GFP-fused SYP71 under control of its native promoter. From these analyses, we concluded that one of the SYP7 subfamily proteins, SYP71, is predominantly expressed in all vegetative tissues and mainly localized to the plasma membrane. We also found that SYP71 is localized to the endoplasmic reticulum in the dividing cells of various types of tissues.

The SNARE Protein SYP71 Expressed in Vascular Tissues Is Involved in Symbiotic Nitrogen Fixation in Lotus japonicus Nodules

“…In Arabidopsis, AtSYP71 is expressed in vegetative tissues and its expression is detected in the vascular tissues of the roots (Suwastika et al, 2008). This pattern is similar to that of LjSYP71 in L. japonicus.…”

“…This pattern is similar to that of LjSYP71 in L. japonicus. However, it should be noted that no homozygous T-DNA insertion mutant of Arabidopsis SYP71 was isolated from progenies of the SYP71/syp71 heterozygote, suggesting that AtSYP71 is essential for the development of Arabidopsis (Suwastika et al, 2008). By contrast, LjSYP71 does not appear to be essential for the development of the L. japonicus plant because under nonsymbiotic conditions but supplied with combined nitrogen, the Ljsyp71 mutant grows similarly to the wild-type plant.…”

“…In Arabidopsis, SYP71 is predominantly localized to the plasma membrane where it is thought to function in the secretion process (Alexandersson et al, 2004;Marmagne et al, 2004;Tyrrell et al, 2007;Suwastika et al, 2008). The discovery of the LjSYP71-defective Fix 2 mutant suggests the existence of a systemic regulation of the nitrogenfixing activity mediated by vascular tissues.…”

Selective Regulation of Maize Plasma Membrane Aquaporin Trafficking and Activity by the SNARE SYP121

“…SYP71 and SYP122 are syntaxins localized in the plasma membrane (Leyman et al, 2000;Borner et al, 2005;Suwastika et al, 2008), while SYP21 was found in the prevacuolar compartment membrane (da Silva Conceição et al, 1997;Sanderfoot et al, 2001;Tse et al, 2004). None of these Sp2 fragments affected the plasma membrane accumulation of mYFP: ZmPIP2;5 (Figures 2A and 2B), although AtSYP21-Sp2 has been shown to be active in suppressing traffic to the (pre)vacuolar compartment (Tyrrell et al, 2007).…”

Voltage-dependent-anion-channels (VDACs) in Arabidopsis have a dual localization in the cell but show a distinct role in mitochondria

“…In plants, dual subcellular distribution of proteins is well documented, but most examples concern proteins targeted to both mitochondria and chloroplasts (reviewed in SilvaFilho 2003 andin Carrie et al 2009a). Only a few studies report on other types of dual-compartmentation, for example for SYP71 in PM and ER (Suwastika et al 2008), and for Cytb5 in mitochondria and ER (Zhao et al 2003). A review of Krause and Krupinska (2009) also reported on several nuclear regulators displaying a second compartmentation in mitochondria or plastids.…”