Ca
            <sup>2+</sup>
            -independent and Ca
            <sup>2+</sup>
            /GTP-binding protein-controlled exocytosis in a plant cell

Homann, Ulrike; Tester, Mark

doi:10.1073/pnas.94.12.6565

Cited by 55 publications

(47 citation statements)

References 37 publications

(36 reference statements)

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“…How do we explain this apparent lack of correlation between Ca 2+ and secretion? First, there is evidence in other plant systems that at least some secretion occurs independently of the [Ca 2+ ] (Homann and Tester, 1997). Second, we note that during normal growth, the [Ca 2+ ] is always high at the apical plasma membrane of the pollen tube.…”

Section: Oscillation Of the Intracellular [Ca 2+ ] Does Not Regulate mentioning

confidence: 60%

Exocytosis Precedes and Predicts the Increase in Growth in Oscillating Pollen Tubes

et al. 2009

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We examined exocytosis during oscillatory growth in lily (Lilium formosanum and Lilium longiflorum) and tobacco (Nicotiana tabacum) pollen tubes using three markers: (1) changes in cell wall thickness by Nomarski differential interference contrast (DIC), (2) changes in apical cell wall fluorescence in cells stained with propidium iodide (PI), and (3) changes in apical wall fluorescence in cells expressing tobacco pectin methyl esterase fused to green fluorescent protein (PME-GFP). Using PI fluorescence, we quantified oscillatory changes in the amount of wall material from both lily and tobacco pollen tubes. Measurement of wall thickness by DIC was only possible with lily due to limitations of microscope resolution. PME-GFP, a direct marker for exocytosis, only provides information in tobacco because its expression in lily causes growth inhibition and cell death. We show that exocytosis in pollen tubes oscillates and leads the increase in growth rate; the mean phase difference between exocytosis and growth is -988 6 38 in lily and -1248 6 48 in tobacco. Statistical analyses reveal that the anticipatory increase in wall material predicts, to a high degree, the rate and extent of the subsequent growth surge. Exocytosis emerges as a prime candidate for the initiation and regulation of oscillatory pollen tube growth.

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Section: Oscillation Of the Intracellular [Ca 2+ ] Does Not Regulate mentioning

confidence: 60%

Exocytosis Precedes and Predicts the Increase in Growth in Oscillating Pollen Tubes

et al. 2009

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“…These changes in capacitance are consistent in size with the predicted vesicle dimensions derived from ultrastructural studies (Picton and Steer, 1983;Phillips et al, 1988) and from imaging studies using fluorescent styryl dyes to label internalized membrane . Factors shown to affect vesicle traffic in plants include cytosol-free Ca 2þ concentration ([Ca 2þ ] i ), guanosine nucleotides (Homann and Tester, 1997;Carroll et al, 1998), and osmotic changes (Kubitscheck et al, 2000). Furthermore, evidence for [Ca 2þ ] i -dependent and -independent exocytotic pathways underscores the complexity of secretory processing that must occur in parallel within individual cells (Homann and Tester, 1997;Sutter et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

Selective Mobility and Sensitivity to SNAREs Is Exhibited by theArabidopsisKAT1 K+ Channel at the Plasma Membrane

et al. 2006

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Recent findings indicate that proteins in the SNARE superfamily are essential for cell signaling, in addition to facilitating vesicle traffic in plant cell homeostasis, growth, and development. We previously identified SNAREs SYP121/Syr1 from tobacco (Nicotiana tabacum) and the Arabidopsis thaliana homolog SYP121 associated with abscisic acid and drought stress. Disrupting tobacco SYP121 function by expressing a dominant-negative Sp2 fragment had severe effects on growth, development, and traffic to the plasma membrane, and it blocked K þ and Cl ÿ channel responses to abscisic acid in guard cells. These observations raise questions about SNARE control in exocytosis and endocytosis of ion channel proteins and their organization within the plane of the membrane. We have used a dual, in vivo tagging strategy with a photoactivatable green fluorescent protein and externally exposed hemagglutinin epitopes to monitor the distribution and trafficking dynamics of the KAT1 K þ channel transiently expressed in tobacco leaves. KAT1 is localized to the plasma membrane within positionally stable microdomains of ;0.5 mm in diameter; delivery of the K þ channel, but not of the PMA2 H þ -ATPase, to the plasma membrane is suppressed by Sp2 fragments of tobacco and Arabidopsis SYP121, and Sp2 expression leads to profound changes in KAT1 distribution and mobility within the plane of the plasma membrane. These results offer direct evidence for SNARE-mediated traffic of the K þ channel and a role in its distribution within subdomains of the plasma membrane, and they implicate a role for SNAREs in positional anchoring of the K þ channel protein.

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“…Homann & Tester (1997) found a small, but steady rise in capacitance that was independent of [Ca# + ] i level in the patch pipette. However, a more rapid increase in capacitance could be evoked at micromolar [Ca# + ] i provided GTP was also present in the solution perfusing the cytosol, and the effect was antagonized by GDPβS.…”

Section: Coupling Secretion To Cytosolic-free Ca# + Concentrationmentioning

confidence: 87%

“…All evidence suggests that the mechanism(s) that give rise to pressure-induced exo-and endocytosis differ fundamentally from Ca# + -dependent secretion in the same tissues (Zorec & Tester, 1993 ;Homann & Tester, 1997 ;Thiel et al, 1999). Very modest hydrostatic pressures gave rates of capacitance rise 50-fold higher than under elevated [Ca# + ] i without evidence of saturation and, in Vicia guard cell protoplasts, was insensitive to [Ca# + ] i (Homann, 1998).…”

Section: Coupling Secretion To Cytosolic-free Ca# + Concentrationmentioning

confidence: 99%

Tansley Review No. 108

1999

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Eukaryotic cells share a set of secretory pathways for the flux of membrane and protein material. In 1993, ideas about the functioning of three major proteins of the neurosecretory complex were consolidated in the SNARE hypothesis, which proposed that the interaction of these proteins provides both the specificity for vesicle targeting and the molecular machinery for fusion between vesicle and target membranes. Subsequetly, the organization, molecular mechanics and control of vesicle trafficking have become topics of intense research, and the hypothesis has evolved to accommodate new discoveries from the analysis of secretion in yeast and mammals. It is likely to be challenged again as more information comes to light about secretory processes in plants. New tools for measuring and manipulating vesicle traffic and secretion are now being used, drawing on in vivo fluorescence and capacitance recording as well as genetic engineering. These new technologies have already begun to yield details wholly unexpected from past studies. Here we focus on recent findings relating to the mechanisms of vesicle trafficking and the background to these developments, highlighting both current understanding of the molecular events of secretion and the gaps therein, as well as discussing emerging themes from work with plants.

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Ca ²⁺ -independent and Ca ²⁺ /GTP-binding protein-controlled exocytosis in a plant cell

Cited by 55 publications

References 37 publications

Exocytosis Precedes and Predicts the Increase in Growth in Oscillating Pollen Tubes

Exocytosis Precedes and Predicts the Increase in Growth in Oscillating Pollen Tubes

Selective Mobility and Sensitivity to SNAREs Is Exhibited by theArabidopsisKAT1 K+ Channel at the Plasma Membrane

Tansley Review No. 108

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Ca 2+ -independent and Ca 2+ /GTP-binding protein-controlled exocytosis in a plant cell

Cited by 55 publications

References 37 publications

Exocytosis Precedes and Predicts the Increase in Growth in Oscillating Pollen Tubes

Exocytosis Precedes and Predicts the Increase in Growth in Oscillating Pollen Tubes

Selective Mobility and Sensitivity to SNAREs Is Exhibited by theArabidopsisKAT1 K+ Channel at the Plasma Membrane

Tansley Review No. 108

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Ca ²⁺ -independent and Ca ²⁺ /GTP-binding protein-controlled exocytosis in a plant cell