Actin Polymerization Is Essential for Pollen Tube Growth

Vidali, Luis; McKenna, Sylvester T.; Hepler, Peter K.

doi:10.1091/mbc.12.8.2534

Cited by 280 publications

(243 citation statements)

References 67 publications

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“…A critical role for the actin cytoskeleton in pollen germination and tube growth (Gibbon et al, 1999;Vidali et al, 2001; this study) led us to hypothesize that actin microfilaments may function in regulating the PM Ca 21 channels during pollen germination and tube growth processes. This idea was also prompted by the observation of Fu et al (2001) or pollen tubes (Fig.…”

Section: Cross-talk Between Dynamic F-actin and Oscillating [Ca 21 ] mentioning

confidence: 89%

Ca2+-Permeable Channels in the Plasma Membrane of Arabidopsis Pollen Are Regulated by Actin Microfilaments

et al. 2004

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Cytosolic free Ca 21 and actin microfilaments play crucial roles in regulation of pollen germination and tube growth. The focus of this study is to test the hypothesis that Ca 21 channels, as well as channel-mediated Ca 21 influxes across the plasma membrane (PM) of pollen and pollen tubes, are regulated by actin microfilaments and that cytoplasmic Ca 21 in pollen and pollen tubes is consequently regulated. In vitro Arabidopsis (Arabidopsis thaliana) pollen germination and tube growth were significantly inhibited by Ca 21 channel blockers La 31 or Gd 31 and F-actin depolymerization regents. The inhibitory effect of cytochalasin D (CD) or cytochalasin B (CB) on pollen germination and tube growth was enhanced by increasing external Ca 21 . Ca 21 fluorescence imaging showed that addition of actin depolymerization reagents significantly increased cytoplasmic Ca 21 levels in pollen protoplasts and pollen tubes, and that cytoplasmic Ca 21 increase induced by CD or CB was abolished by addition of Ca 21 channel blockers. By using patch-clamp techniques, we identified the hyperpolarization-activated inward Ca 21 currents across the PM of Arabidopsis pollen protoplasts. The activity of Ca 21 -permeable channels was stimulated by CB or CD, but not by phalloidin. However, preincubation of the pollen protoplasts with phalloidin abolished the effects of CD or CB on the channel activity. The presented results demonstrate that the Ca 21 -permeable channels exist in Arabidopsis pollen and pollen tube PMs, and that dynamic actin microfilaments regulate Ca 21 channel activity and may consequently regulate cytoplasmic Ca 21 .The primary function of pollen and pollen tubes is to deliver sperms to egg apparatus for double fertilization that is required for sexual reproduction of flowering plants. Pollen germination and pollen tube growth are a continuous and highly polarized process characteristic of tip growth; thus pollen and pollen tubes provide an ideal model system for the study of cell polarity control and tip growth. It is well known that extracellular Ca 21 is required for pollen germination and tube growth (for review, see Steer and Steer, 1989;Taylor and Hepler, 1997;Malhó , 1998;Franklin-Tong, 1999), which indicates a possible involvement of Ca 21 influx in pollen germination and tube growth. Upon pollen hydration and germination, cytoplasmic Ca 21 concentration ([Ca 21 ] i ) at the germinal aperture where the pollen tube emerges increases to a higher level than other regions, and a tip-focused Ca 21 gradient is then established and sustained while a pollen tube grows forward (Rathore et al., 1991;Pierson et al., 1994;Feijó et al., 1995). Disruption or modification of the Ca 21 gradient inhibits pollen tube growth (Miller et al., 1992) or changes its growth direction (Malhó and Trewavas, 1996). The tip-focused Ca 21 gradient oscillates in the pollen tubes of lily (Lilium longiflorum) and other species (Holdaway-Clarke et al., 1997;Messerli and Robinson, 1997;Messerli et al., 2000). Ca 21 mobilization from intracellular Ca...

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Section: Cross-talk Between Dynamic F-actin and Oscillating [Ca 21 ] mentioning

confidence: 89%

Ca2+-Permeable Channels in the Plasma Membrane of Arabidopsis Pollen Are Regulated by Actin Microfilaments

et al. 2004

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“…The pumping of H 1 creates a local gradient that likely affects the structure and activity of the nearby cortical actin fringe, as well as membrane transport activities. Second, actin polymerization, which favors G-actin bound with ATP, is essential for pollen tube elongation (Gibbon et al, 1999;Vidali et al, 2001) and participates in the formation of the prominent cortical actin fringe (Lovy-Wheeler et al, 2005). It is additionally pertinent that the dephosphorylation of F-actin ATP renders the filament sensitive to remodeling by the pH-sensitive actin-binding protein ADF (Blanchoin and Pollard, 1999).…”

Section: Discussionmentioning

confidence: 99%

NAD(P)H Oscillates in Pollen Tubes and Is Correlated with Tip Growth

et al. 2006

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“…This process is also not affected in the pilz group mutants, as there was no segregation distortion that would suggest reduced transmission through the haploid gametophytes. Thus, tip growth of the pollen tube does not require microtubules, whereas actin filaments appear to play an essential role (Vidali et al 2001).…”

Section: Genetic Ablation Of Microtubules Reveals Their Functional Rementioning

confidence: 99%

The Arabidopsis PILZ group genes encode tubulin-folding cofactor orthologs required for cell division but not cell growth

Steinborn¹,

Maulbetsch²,

Priester³

et al. 2002

Genes Dev.

162

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Plant microtubules are organized into specific cell cycle-dependent arrays that have been implicated in diverse cellular processes, including cell division and organized cell expansion. Mutations in four Arabidopsis genes collectively called the PILZ group result in lethal embryos that consist of one or a few grossly enlarged cells. The mutant embryos lack microtubules but not actin filaments. Whereas the cytokinesis-specific syntaxin KNOLLE is not localized properly, trafficking of the putative auxin efflux carrier PIN1 to the plasma membrane is normal. The four PILZ group genes were isolated by map-based cloning and are shown to encode orthologs of mammalian tubulin-folding cofactors (TFCs) C, D, and E, and associated small G-protein Arl2 that mediate the formation of ␣/␤-tubulin heterodimers in vitro. The TFC C ortholog, PORCINO, was detected in cytosolic protein complexes and did not colocalize with microtubules. Another gene with a related, although weaker, embryo-lethal phenotype, KIESEL, was shown to encode a TFC A ortholog. Our genetic ablation of microtubules shows their requirement in cell division and vesicle trafficking during cytokinesis, whereas cell growth is mediated by microtubule-independent vesicle trafficking to the plasma membrane during interphase. The microtubule cytoskeleton plays important roles in both nondividing and dividing cells of eukaryotes, assisting in vesicle trafficking and mediating proper segregation of daughter chromosomes to opposite poles during mitosis (for review, see Cole and Lippincott-Schwartz 1995;Straight and Field 2000). In fission yeast, microtubules have also been implicated in maintaining cell shape and polarity (Sawin and Nurse 1998). Higher-plant cells form their own specific microtubule arrays, such as cortical hoops of interphase microtubules that organize cell elongation (Whittington et al. 2001), and two arrays related to the plant-specific mode of cell division (for review, see Lloyd and Hussey 2001). The preprophase band forms transiently at the onset of mitosis and marks the cortical division site (for review, see Smith 2001). The phragmoplast forms at the center of the division plane in late anaphase and guides the delivery of Golgiderived vesicles. Their fusion results in the formation and lateral expansion of the cell plate that matures into a cell wall and flanking plasma membranes (for review, see Staehelin and Hepler 1996). Both preprophase band and phragmoplast also contain actin filaments; however, their specific role in plant cell division is not understood at present (Smith 2001).Microtubules are polymerized from ␣/␤-tubulin heterodimers (for review, see Nogales 2000). Newly synthesized ␣-and ␤-tubulin polypeptides undergo a sequence of folding steps catalyzed by chaperones. Initially, the tubulins are associated with the hexameric prefoldin complex that passes them on to the cytosolic chaperonin complex (Geissler et al. 1998;Vainberg et al. 1998;Hansen et al. 1999; for review, see Leroux and Hartl 2000;Llorca et al. 2000). Whereas fully func...

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Actin Polymerization Is Essential for Pollen Tube Growth

Cited by 280 publications

References 67 publications

Ca2+-Permeable Channels in the Plasma Membrane of Arabidopsis Pollen Are Regulated by Actin Microfilaments

Ca2+-Permeable Channels in the Plasma Membrane of Arabidopsis Pollen Are Regulated by Actin Microfilaments

NAD(P)H Oscillates in Pollen Tubes and Is Correlated with Tip Growth

The Arabidopsis PILZ group genes encode tubulin-folding cofactor orthologs required for cell division but not cell growth

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