Tubular and filamentous structures in pollen tubes: Possible involvement as guide elements in protoplasmic streaming and vectorial migration of secretory vesicles

Abstract

An ultrastructural study of the pollen tubes of Lilium and Clivia has demonstrated three different classes of longitudinal structures which could influence patterns of protoplasmic streaming and/or serve as "guide elements" in the vectorial migration of secretory vesicles: (a), cortical and noncortical microtubules; (b), microfilaments; and (c), subcortical tubules and cisternae of the endoplasmic reticulum ("subsurface cisternae"). Morphological details of these structures are described. Colchicine concentrations which lead to the complete disappearance of the microtubules affect neither germination of the pollen nor cytoplasmic streaming and tip growth of the elongating pollen tubes. Tip growth is initially uninhibited by cycloheximide, and cytoplasmic streaming is insensitive to this inhibitor. However, both of these processes are sensitive to cytochalasin B and vinblastine. Our results suggest that neither microtubules nor subsurface cisternae are essential for cytoplasmic streaming and directional secretion of cell surface materials in the pollen tube but would be consistent with an involvement of microfilamentous structures in these processes. Additionally, the possible importance of the lateral cross-link elements interconnecting all three types of structures is discussed.

Annulate lamellae in plant cells: Formation during microsporogenesis and pollen development in Canna generalis Bailey

“…The occurrence of pore complexes in such cist ernae has until now not been documented for plant material, although Skvarla (quoted in the addendum to K essel's review, 1968) and Sheridan and Barrnett (1969) have mentioned th e existen ce of AL in meiocytes and in growing poll en of Lilium and Canna, resp ectively. W e have recently shown that single annulate cisternae can be found in both the nucleoplasm and th e cytoplasm of cultured plant cells (Franke et al, 1972). The present study which confirms the remark of Skvarla represents to our knowledge the first documentation of stacked AL in plant cells.…”

Actin Organization and Distribution during Hydration, Activation and Germination of Pollen in Amaryllis vittata Ait. Using TRITC-phalloidin as a Probe.

“…It is well known that actin plays an important role in pollen germination and pollen tube emergence as the basis of cytoplasm streaming from previous studies (Tiwari and Polito 1990, Derkson and Traas 1985, Heslop-Harrison and Heslop-Harison 1989a, Franke et al 1972. In the present report, the inhibition of pollen germination by cytochalasin D supported the consideration of the significance of actin on pollen activation and germination.…”

“…Furthermore, using dimethylsulphoxide (DMSO) as a permeabilising agent instead of the aldehyde fixation improved the image of microfilament in the pollen grain and pollen tube (Pierson 1988). Up to date, many reports confirm that the microfilament is one of the normal component of the cell structure and plays an important role in cytoplasm dynamics during pollen germination and pollen tube growth (Tiwari and Polito 1989, Heslop-Harrison and Heslop-Harrison 1988, 1989a, b, c, d, 1991, Heslop-Harrison et al 1986, 1988, Franke et al 1972). However, very little attention has been paid to the aspects of microfilament organization during the period that precedes pollen germination.…”

Pollen tube tip growth

“…Cytochalasins, which lead to shortening of actin filaments that have a rapid turnover (Flanagan & Lin, 1980;Schliwa, 1982;Burgoyne & Cheek, 1987;Cooper, 1987) inhibit cytoplasmic streaming (Franke et al, 1972;Mascarenhas & I^afountain, 1972), tube growth (Mascarenhas & Lafountain, 1972) and movement of secretory vesicles to the tube tip (Picton & Steer, 1981). Generally cytochalasins are believed to have variable effects on plant cell systems (Staiger & Schliwa, 1987) and they also do not appear to interfere with exocytosis in animal cell secretory systems (Burgoyne & Cheek, 1987).…”