Conjugation Process in Spirogyra varians Monitored with FITC-lectins(Zygnemataceae, Chlorophyta)

In Spirogyra, two compatible filaments align parallel to each other making numerous papillae, which connect the opposite cells during conjugation and serve as a passage for a male cytoplasm to move into the female cell (Hoek et al. 1995; Sze 1998; Kim et al. 2007). Conjugation process involves a complex series of events but it always begins with the contact between two papillae protruded from each opposite cell. Therefore, recognition factors are expected along their surfaces. Although there are few studies on the environmental factors inducing conjugation in the zygnematacean species (Grote 1977; Simons et al. 1984; Stabenau and Saeftel 1989; Kato and Ooshima 1997), the key factors which trigger the conjugation and the mechanism of recognition between the compatible filaments are still unknown (Kim et al. 2007). Cell surface carbohydrates are highly suitable for encoding biological information because of their complexity and structural diversity, and hence they have been reported as primary markers for cell-cell recognition events in many organisms (Sharon and Lis 1993, Kim and Kim 1999). Such recognition systems depend on the complementary binding between carbohydrate moieties of a glycoconjugate on one cell with a lectin protein on another cell (Sharon and Lis 1989; Chrispeels and Raikhel 1991; Kim and Kim 1999; Kim et al. 2005). Because of their sugar-binding properties, fluoresceinlabeled lectins have been used as a powerful tool to analyze the characteristics and the distribution of cell surface carbohydrates in many organisms (e.g. Wassarman 1987; Sharon and Lis 1989; Karlsson 1991; Kim and Fritz 1993a, b; Kim et al. 1996; Kim and Kim 1999). Cheli and De Vecchi (1989) showed that the extracellular mucilage of Spirogyra filaments disappeared during conjugation and some glycoproteinaceous materials were accumulated in the cell wall of the developing conjugation papilla, suggesting that the chemical composition in cell surface changed during the process. Our previous study on the conjugation process of Zygnema cruciatum also showed that the surface carbohydrate moiety changes during the conjugation and newly appeared glyAlgae Volume 24(1): 39-45, 2009