Differential roles of microtubule and actin-myosin cytoskeleton in the growth of Pinus pollen tubes

Imaging of Dynamic Secretory Vesicles in Living Pollen Tubes of Picea meyeri Using Evanescent Wave Microscopy

“…In our study, however, we found that in gymnosperm the staining pattern at the tube apex did not correspond spatially to the previously described V-shaped, apical clear zone containing secretory vesicles, confirming that the cytoplasmic organization of gymnosperm pollen tubes was distinct from that of angiosperm pollen tubes (Justus et al, 2004;Chen et al, 2006). In previous studies, some organelles moved linearly, in a mostly circulatory pattern (Cai et al, 2001), whereas the majority of organelles in Pinus sylvestris pollen tubes exhibited Brownian-like motions (Terasaka and Niitsu, 1994;de Win et al, 1996). The experiments described herein clearly show that vesicles were significantly held back when they moved, and that two classes of secretory vesicle motions are present.…”

Microtubules and microfilaments are both responsible for pollen tube elongation in the coniferPicea abies (Norway spruce)

“…Pinus pollen tubes are extremely branched both in vivo and in vitro (Singh 1978). This branching occurs by bifurcation of the tip (de Win et al 1996) and is increased by colchicine treatment (Terasaka and Niitsu 1994). The threshold concentrations for significant branching in P. abies were similar to the thresholds for inhibition of tube elongation caused by APM, oryzalin, and propyzamide.…”

“…Myosin inhibition with NEM stops organelle motility in Lilium longiflorum pollen tubes (Kohno and Shimmen 1988), and myosin is detected throughout angiosperm pollen tubes (Tang et al 1989, Miller et al 1995, Yokota et al 1995. In conifers, microfilaments form an axial array in the pollen tube (Terasaka and Niitsu 1994, de Win et al 1996, Lazzaro 1996. In chemically fixed material labeled with rhodamine-phalloidin (Lazzaro 1996) or immunolabeled with actin antibodies (Fig.…”

“…Kinesin-like molecules are localized in the tip (Tiezzi et al 1992, Cai et al 1993) and dynein-like molecules throughout the tube (Moscatelli et al 1998), but the function of these putative microtubule motor proteins in elongation is unknown. In conifers, microtubules form a net axial array (Terasaka andNiitsu 1994, Lazzaro 1999) and this array extends throughout the pollen tube and is not concentrated in the cell cortex (Lazzaro 1999). Microtubules also extend to the tip, where they are enriched in a radial array beneath the plasma membrane.…”

“…Little is known about the physiological function of the cytoskeleton in conifer tube growth. There is qualitative evidence in Pinus densiflora that microfilament disruption inhibits tube growth, myosin inhibition blocks germination, and microtubule disruption induces additional branching (Terasaka and Niitsu 1994).…”