The <i>roothairless1</i> Gene of Maize Encodes a Homolog of <i>sec3</i>, Which Is Involved in Polar Exocytosis

Wen, Tsui-Jung; Hochholdinger, Frank; Sauer, M.R.; Bruce, William A.; Schnable, Patrick S.

doi:10.1104/pp.105.062174

Cited by 171 publications

(160 citation statements)

References 37 publications

(51 reference statements)

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“…S9A, white arrows). In root hair cells, where active exocytosis is required for polarized growth (33,34), it was found that, upon ES2 treatment, the fluorescence recovery of GFP:EXO70A1 after photobleaching was significantly slower compared with control cells (Fig. 4D).…”

Section: The Expression Of Exo70a1 N Terminus Results In Desensitizatmentioning

confidence: 99%

Endosidin2 targets conserved exocyst complex subunit EXO70 to inhibit exocytosis

Zhang

Brown

Ven

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

129

143

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The exocyst complex regulates the last steps of exocytosis, which is essential to organisms across kingdoms. In humans, its dysfunction is correlated with several significant diseases, such as diabetes and cancer progression. Investigation of the dynamic regulation of the evolutionarily conserved exocyst-related processes using mutants in genetically tractable organisms such as Arabidopsis thaliana is limited by the lethality or the severity of phenotypes. We discovered that the small molecule Endosidin2 (ES2) binds to the EXO70 (exocyst component of 70 kDa) subunit of the exocyst complex, resulting in inhibition of exocytosis and endosomal recycling in both plant and human cells and enhancement of plant vacuolar trafficking. An EXO70 protein with a C-terminal truncation results in dominant ES2 resistance, uncovering possible distinct regulatory roles for the N terminus of the protein. This study not only provides a valuable tool in studying exocytosis regulation but also offers a potentially new target for drugs aimed at addressing human disease.T he EXO70 (exocyst component of 70 kDa) protein is a component of the evolutionarily conserved octameric exocyst complex that tethers post-Golgi vesicles to the plasma membrane before SNARE-mediated membrane fusion (1). As an important component of the exocyst complex that mediates exocytosis, EXO70 regulates, for example, neurite outgrowth, epithelial cell polarity establishment, cell motility, and cell morphogenesis in animal cells (2-6). In plants, EXO70 proteins participate in polarized pollen tube growth, root hair growth, deposition of cell wall material, cell plate initiation and maturation, defense, and autophagy (7-12). In humans, EXO70 mediates the trafficking of the glucose transporter Glut4 to the plasma membrane that is stimulated by insulin and involved in the development of diabetes (13). A specific isoform of human EXO70 is also involved in cancer cell invasion (13-15). Endosidin2 (ES2) was identified from a plantbased chemical screen as an inhibitor of trafficking. We demonstrate that the target of ES2 is the EXO70 subunit of the exocyst and that ES2 is active in plants and mammalian systems. Significantly, no inhibitor of the exocyst complex has been reported, yet such compounds could be important for understanding the basic mechanisms of exocyst-mediated processes, for modifying secretion in biotechnological applications, and for the development of potential new drugs with higher affinity and more potent activity to control exocyst-related diseases. Results ES2 InhibitsTrafficking to the Plasma Membrane. ES2 is a previously identified plant endomembrane trafficking disruptor (Fig. 1A) that inhibits polarized growth of pollen tubes in a dose-dependent manner (Fig. S1 A and B) (16). Arabidopsis seedlings grown on media containing ES2 have shorter roots and fewer and shorter root hairs and are less sensitive to gravity stimulation (Fig. S1 C-G). ES2 disrupted the trafficking of proteins that are actively recycled between the plasma membrane and endosome...

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Section: The Expression Of Exo70a1 N Terminus Results In Desensitizatmentioning

confidence: 99%

Endosidin2 targets conserved exocyst complex subunit EXO70 to inhibit exocytosis

Zhang

Brown

Ven

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

129

143

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“…The essential function of the exocyst in tip growth in plants has already been demonstrated by genetic studies, although the exact role of the exocyst has not been elucidated yet. Mutations of SEC3 in maize and EXO70A1 in Arabidopsis lead to impaired root hair elongation (Wen et al, 2005;Synek et al, 2006). Mutations of SEC3, SEC5, SEC6, SEC8, and SEC15a in Arabidopsis dramatically affect both pollen germination and pollen tube elongation (Cole et al, 2005;Hála et al, 2008).…”

Section: Functions Of Exo70 Genes In Tip Growthmentioning

confidence: 99%

“…Immunocytochemical analysis showed that SEC6, SEC8, and EXO70A1(At5g03540) are colocalized in tips of growing pollen tubes, which seems to be similar to the polarized localization to the sites of secretion of the exocyst complex in yeast and animals (Hála et al, 2008). Mutations of both SEC3 in maize (Zea mays) and EXO70A1 in Arabidopsis cause a defect in root hair elongation (Wen and Schnable, 1994;Wen et al, 2005), whereas mutations of SEC3, SEC5, SEC6, SEC8, or SEC15a in Arabidopsis lead to defects in pollen germination and pollen tube growth (Cole et al, 2005;Hála et al, 2008). One of these EXO84 genes in Arabidopsis is involved in secretion processes during cytokinesis (Fendrych et al, 2010).…”

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confidence: 99%

Expression and Functional Analyses ofEXO70Genes in Arabidopsis Implicate Their Roles in Regulating Cell Type-Specific Exocytosis

Ren

et al. 2010

Plant Physiology

107

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During exocytosis, Golgi-derived vesicles are tethered to the target plasma membrane by a conserved octameric complex called the exocyst. In contrast to a single gene in yeast and most animals, plants have greatly increased number of EXO70 genes in their genomes, with functions very much unknown. Reverse transcription-polymerase chain reactions were performed on all 23 EXO70 genes in Arabidopsis (Arabidopsis thaliana) to examine their expression at the organ level. Cell-level expression analyses were performed using transgenic plants carrying β-glucuronidase reporter constructs, showing that EXO70 genes are primarily expressed in potential exocytosis-active cells such as tip-growing and elongating cells, developing xylem elements, and guard cells, whereas no expression was observed in cells of mature organs such as well-developed leaves, stems, sepals, and petals. Six EXO70 genes are expressed in distinct but partially overlapping stages during microspore development and pollen germination. A mutation in one of these genes, EXO70C1 (At5g13150), led to retarded pollen tube growth and compromised male transmission. This study implies that multiplications of EXO70 genes may allow plants to acquire cell type- and/or cargo-specific regulatory machinery for exocytosis.

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“…Vesicle fusion is accomplished through the action of SNARE proteins (for review, see Lipka et al, 2007), tethering factors (Rab GTPases; for review, see Zerial and McBride, 2001;Molendijk et al, 2004), and presumably aided by components of the exocyst complex (Segui-Simarro et al, 2004), although, to date, mutants defective in subunits of this complex have only been implicated in polar growth (Cole et al, 2005;Wen et al, 2005;Synek et al, 2006;Lavy et al, 2007). The darkstained vesicles were also found in the vicinity of the Golgi apparatus, and it was concluded that they were Golgi derived.…”

Section: Origin Of Cell Plate-building Vesiclesmentioning

confidence: 99%

Vesicle Trafficking during Somatic Cytokinesis

2008

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The roothairless1 Gene of Maize Encodes a Homolog of sec3, Which Is Involved in Polar Exocytosis

Cited by 171 publications

References 37 publications

Endosidin2 targets conserved exocyst complex subunit EXO70 to inhibit exocytosis

Endosidin2 targets conserved exocyst complex subunit EXO70 to inhibit exocytosis

Expression and Functional Analyses ofEXO70Genes in Arabidopsis Implicate Their Roles in Regulating Cell Type-Specific Exocytosis

Vesicle Trafficking during Somatic Cytokinesis

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