Analysis of the Structure, Organization and Role of Cytoskeleton During Pollen Germination and Tube Growth in Pyrus communis L.

Abstract

Behavior of actin microfilaments and microtubules was followed in the vegetative cell of germinating pollen and pollen tubes of pyrus communis using rhodamine-conjugated phalloidin to visualize actin, indirect immunofluorescence to localize microtubules, and conventional and freeze-substitution electron microscopy. Several previous investigations have focused on the cytoskeleton of pollen tubes at the ultrastructural level (Franke et al., 1972; Miki-Hirosige & Nakamura, 1982; Derksen et al., 1985; Tiezzi et al., 1986 Lancelle et al., 1987) and at the light microscope level (Derksen et al., 1985; Perdue & Parthasarathy, 1985; Pierson et al., 1985; Tiezzi et alata., 1986) using fluorescent probes. However, questions remain about the precise organization of the pollen tube cytoskeleton, and there has been scant attention to dynamics of cytoskeletal elements during the periods of pollen hydration and activation that precede germination. Pollen Activation. By using the actin-specific probe, rhodamineconjugated phalloidin (RP), to study the dynamics of actin microfilaments, we identified several stages of actin organization as dehydrated pollen grains become activated and eventually germinate.