The Syntaxins SYP31 and SYP81 Control ER–Golgi Trafficking in the Plant Secretory Pathway

Abstract

†These authors contributed equally to this work.Overexpression of the Golgi and endoplasmic reticulum (ER) syntaxins SYP31 and SYP81 strongly inhibits constitutive secretion. By comparing the secreted reporter a-amylase with the ER-retained reporter a-amylase-HDEL, it was concluded that SYP81 overexpression inhibits both retrograde and anterograde transport, while SYP31 overexpression mainly affected anterograde transport. Of the other interacting SNAREs investigated, only the overexpression of MEMB11 led to an inhibition of protein secretion. Although the position of a fluorescent tag does not influence the correct localization of the fusion protein, only N-terminal-tagged SYP31 retained the ability of the untagged SNARE to inhibit transport. C-terminal-tagged SYP31 failed to exhibit this effect. Overexpression of both wild-type and N-terminal-tagged syntaxins caused standard Golgi marker proteins to redistribute into the ER. Nevertheless, green fluorescent protein (GFP)-SYP31 was still visible as fluorescent punctae, which, unlike SYP31-GFP, were resistant to brefeldin A treatment. Immunogold electron microscopy showed that endogenous SYP81 is not only present at the ER but also in the cis Golgi, indicating that this syntaxin cycles between these two organelles. However, when expressed at non-inhibitory levels, YFP-SYP81 was seen to locate principally to subdomains of the ER. These punctate structures were physically separated from the Golgi, suggesting that they might possibly reflect the position of ER import sites.

The heterologous expression of aGlycine maxhomolog of NONEXPRESSOR OF PR1 (NPR1) and α-hydroxynitrile glucosidase suppresses parasitism by the root pathogenMeloidogyne incognitainGossypium hirsutum

“…Such a role for the plant secretion system has been determined in the G. max-H. glycines pathosystem with the identification of alpha-soluble N-ethylmaleimide-sensitive factor attachment protein (α-SNAP) composing part of the major H. glycines resistance locus rhg1 in G. max (Matsye et al , 2012. These results were confirmed by the observation that overexpression of the α-SNAP interacting protein, syntaxin 31 (Gm-SYP38), known to function at the cis face of the Golgi apparatus, functions effectively to impair H. glycines parasitism (Banfield et al 1995;Lupashin et al 1997;Leyman et al 1999;Collins et al 2003;Peng & Gallwitz 2004;Bubeck et al 2008;Pant et al 2014;Pant, Krishnavajhala et al 2015). In contrast, suppressed Gm-SYP38 expression in the H. glycines-resistant genotype G. max [Peking/PI 548402] results in the normally resistant genotype becoming susceptible to the parasite (Pant et al 2014).…”

An Arabidopsis Prenylated Rab Acceptor 1 Isoform, AtPRA1.B6, Displays Differential Inhibitory Effects on Anterograde Trafficking of Proteins at the Endoplasmic Reticulum

“…Furthermore, the inhibitory effect of AtPRA1.B6 on anterograde trafficking appears to differ from that of SNARE SYP31 and SYP81 overexpression. SNARE overexpression inhibits the trafficking of not only secreted a-amylase but also the Golgi-localized proteins ST:GFP and Man: GFP (Bubeck et al, 2008). However, the mechanism by which Golgi-localized proteins escape the inhibition is not clearly understood.…”

The syntaxin 31-induced gene, LESION SIMULATING DISEASE1 (LSD1), functions inGlycine maxdefense to the root parasiteHeterodera glycines

“…Syntaxin 31 functions at the cis face of the Golgi apparatus to facilitate the fusion of transport vesicles transported from the endoplasmic reticulum. 3,4,44,[85][86][87][88] In G. max, the overexpression of a-SNAP and Gm-SYP38 results in induced levels of the SA signaling genes EDS1, NPR1 and PR1. 9 While the observation of an influence of vesicle transport on SA signaling is not a new concept, 7 the results of Pant et al 9 indicates that SA signaling may be important to the process of defense in the G. max-H. glycines pathosystem.…”