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F-actin cytoskeleton and cell wall morphogenesis in brown algae
Cell Biology International
Cell Biology International 27 (2003) 209–210
www.elsevier.com/locate/jnlabr/ycbir
Short communication
F-actin cytoskeleton and cell wall morphogenesis in brown algae C. Katsaros *, D. Karyophyllis, B. Galatis Department of Botany, Faculty of Biology, University of Athens, Athens 157 84, Greece Accepted 14 October 2002
The role of cytoskeleton in cell wall morphogenesis is well established in higher plants (Fowler and Quatrano, 1997). Cortical microtubules (MTs) have been shown to determine, directly or indirectly, cellulose microfibril (MF) orientation in higher plant cells, possibly defining the distribution of cellulose synthesizing enzymes in the plasmalemma. This is also the case in algae possessing cortical MTs (Cyr, 1994; Mizuta, 1992; Tsekos, 1999). Contrary to the above, vegetative cells of brown algae lack a cortical MT cytoskeleton, and are characterized by centriole-bearing centrosomes, which are the microtubule organizing centers of all the cell MTs (Katsaros and Galatis, 1992; Katsaros et al., 1983). Extensive electron microscope and immunofluorescence studies of MT organization in different types of brown algal cells have shown that they constitute a major part of the cytoskeleton, participating in mitosis and cytokinesis, as well as in the expression of polarity of * Corresponding author. Tel.: +30-10-7274652; fax: +30-10-7274702. E-mail address: [email protected] (C. Katsarost).
particular cell types (Karyophyllis et al., 1997; Katsaros, 1992; Katsaros and Galatis, 1992; Katsaros et al., 1983). Using a modified protocol for F-actin staining with rhodamine-phalloidin (Rh-Ph), we found that vegetative cells of brown algae bear a well organized cytoskeleton of actin filaments (AFs), consisting of perinuclear, cytoplasmic and cortical AF arrays (Karyophyllis et al., 2000a). It was found that the cortical AF system shows particular arrangements in different types of cells. In the tip-growing tubular apical cells of Sphacelaria rigidula the cortical AF organization is quite complicated: randomly oriented AFs traverse the dome area, a transverse ring of AFs is formed at the base of the dome, while longitudinal or helical AF arrangement characterizes the tubular part of the cell. Examination of thin sections of the above apical cells under transmission electron microscope (TEM) revealed a mutual arrangement between AFs and the newly depositing cellulose MFs of the cell wall, i.e. randomly oriented cellulose MFs in
Fig. 1. Rh-Ph staining of F-actin in meristematic cells of D. dichotoma. A transverse orientation of AFs is clearly visible in all cells. Fig. 2. Cell wall structure in meristematic cells of D. dichotoma (TEM). Normal cell. The transverse orientation of the MFs is obvious. Fig. 3. Cell wall structure in meristematic cells of D. dichotoma (TEM). CB treated cell. No orientation is observed in the MFs of the innermost cell wall layer. 1065-6995/03/$ - see front matter 2003 Published by Elsevier Science Ltd. doi:10.1016/S1065-6995(02)00312-8
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C. Katsaros et al. / Cell Biology International 27 (2003) 209–210
the dome, transverse arrangement of cellulose MFs at the base of the apical hemisphere and axial or fishbone pattern of cellulose MFs in the cylindrical part of the cell (Karyophyllis et al., 2000b). In order to examine whether the above relationship is a general phenomenon in brown algal cells, the organization of MFs and the underlying AFs were investigated by TEM and Rh-Ph staining, respectively, in a variety of species and cell types, i.e.: differentiating cells of S. rigidula, apical cells of Dictyota dichotoma, subapical cells of Choristocarpus tenellus, and meristematic cells of D. dichotoma (Figs. 1 and 2). In all cases it was found that a cortical AF system was present, always oriented parallel to the depositing MFs of the innermost wall layer (Katsaros et al., 2002). Although it is not possible to confirm the coincidence of AF-MF orientation using TEM, the mutual alignment between cortical AFs and MFs is a strong evidence that AFs are involved in cell wall morphogenesis of brown algae. To investigate further the above hypothesis, we disturbed actin cytoskeleton with cytochalasin B (CB) in order to ascertain whether MF deposition would be affected. Treatment of D. dichotoma thalli with 100 µg/ml CB for 24–36 h caused a gradual disruption of AFs. TEM examination of these cells showed that the MFs of the internal wall surface did not exhibit the clear transverse arrangement observed in normal cells. Instead, a rather random orientation of loose and thin MFs was found (Fig. 3). Misoriented MFs were also observed in CB treated cells of S. rigidula.
References Cyr RJ. Microtubules in plant morphogenesis: role of the cortical array. Ann Rev Cell Biol 1994;10:153–80. Fowler JE, Quatrano RS. Plant cell morphogenesis: plasma membrane interactions with the cytoskeleton and cell wall. Ann Rev Cell Dev Biol 1997;13:697–743. Karyophyllis D, Galatis B, Katsaros C. Centrosome and microtubule dynamics in apical cells of Sphacelaria rigidula (Phaeophyceae) treated with nocodazole. Protoplasma 1997;199:161–72. Karyophyllis D, Katsaros C, Dimitriadis I, Galatis B. F-actin organization during the cell cycle of Sphacelaria rigidula (Phaeophyceae). Eur J Phycol 2000a;35:25–33. Karyophyllis D, Katsaros C, Galatis B. F-actin involvement in apical cell morphogenesis of Sphacelaria rigidula (Phaeophyceae): mutual alignment between cortical actin filaments and cellulose microfibrils. Eur J Phycol 2000b;35:195–203. Katsaros C. Immunofluorescence study of microtubule organization in some polarized cell types of selected brown algae. Bot Acta 1992; 105:400–6. Katsaros C, Galatis B. Immunofluorescence and electron microscope studies of microtubule organization during the cell cycle of Dictyota dichotoma (Phaeophyta, Dictyotales). Protoplasma 1992; 169:75–84. Katsaros C, Galatis B, Mitrakos K. Fine structural studies on the interphase and dividing apical cells of Sphacelaria tribuloides (Phaeophyta). J Phycol 1983;19:16–30. Katsaros C, Karyophyllis D, Galatis B. Cortical F-actin underlies cellulose microfibril patterning in brown algal cells. Phycologia 2002;41:178–83. Mizuta S. Microtubules controlling cellulose deposition? A comparison between Chlorococcales and the giant green coenocytes. In: Menzel D, editor. The cytoskeleton of the algae. Boca Raton: CRC Press, 1992;149–63. Tsekos I. The sites of cellulose synthesis in algae: diversity and evolution of cellulose synthesizing enzyme complexes. J Phycol 1999;35:635–55.
Cell Biology International 27 (2003) 209–210
www.elsevier.com/locate/jnlabr/ycbir
Short communication
F-actin cytoskeleton and cell wall morphogenesis in brown algae C. Katsaros *, D. Karyophyllis, B. Galatis Department of Botany, Faculty of Biology, University of Athens, Athens 157 84, Greece Accepted 14 October 2002
The role of cytoskeleton in cell wall morphogenesis is well established in higher plants (Fowler and Quatrano, 1997). Cortical microtubules (MTs) have been shown to determine, directly or indirectly, cellulose microfibril (MF) orientation in higher plant cells, possibly defining the distribution of cellulose synthesizing enzymes in the plasmalemma. This is also the case in algae possessing cortical MTs (Cyr, 1994; Mizuta, 1992; Tsekos, 1999). Contrary to the above, vegetative cells of brown algae lack a cortical MT cytoskeleton, and are characterized by centriole-bearing centrosomes, which are the microtubule organizing centers of all the cell MTs (Katsaros and Galatis, 1992; Katsaros et al., 1983). Extensive electron microscope and immunofluorescence studies of MT organization in different types of brown algal cells have shown that they constitute a major part of the cytoskeleton, participating in mitosis and cytokinesis, as well as in the expression of polarity of * Corresponding author. Tel.: +30-10-7274652; fax: +30-10-7274702. E-mail address: [email protected] (C. Katsarost).
particular cell types (Karyophyllis et al., 1997; Katsaros, 1992; Katsaros and Galatis, 1992; Katsaros et al., 1983). Using a modified protocol for F-actin staining with rhodamine-phalloidin (Rh-Ph), we found that vegetative cells of brown algae bear a well organized cytoskeleton of actin filaments (AFs), consisting of perinuclear, cytoplasmic and cortical AF arrays (Karyophyllis et al., 2000a). It was found that the cortical AF system shows particular arrangements in different types of cells. In the tip-growing tubular apical cells of Sphacelaria rigidula the cortical AF organization is quite complicated: randomly oriented AFs traverse the dome area, a transverse ring of AFs is formed at the base of the dome, while longitudinal or helical AF arrangement characterizes the tubular part of the cell. Examination of thin sections of the above apical cells under transmission electron microscope (TEM) revealed a mutual arrangement between AFs and the newly depositing cellulose MFs of the cell wall, i.e. randomly oriented cellulose MFs in
Fig. 1. Rh-Ph staining of F-actin in meristematic cells of D. dichotoma. A transverse orientation of AFs is clearly visible in all cells. Fig. 2. Cell wall structure in meristematic cells of D. dichotoma (TEM). Normal cell. The transverse orientation of the MFs is obvious. Fig. 3. Cell wall structure in meristematic cells of D. dichotoma (TEM). CB treated cell. No orientation is observed in the MFs of the innermost cell wall layer. 1065-6995/03/$ - see front matter 2003 Published by Elsevier Science Ltd. doi:10.1016/S1065-6995(02)00312-8
210
C. Katsaros et al. / Cell Biology International 27 (2003) 209–210
the dome, transverse arrangement of cellulose MFs at the base of the apical hemisphere and axial or fishbone pattern of cellulose MFs in the cylindrical part of the cell (Karyophyllis et al., 2000b). In order to examine whether the above relationship is a general phenomenon in brown algal cells, the organization of MFs and the underlying AFs were investigated by TEM and Rh-Ph staining, respectively, in a variety of species and cell types, i.e.: differentiating cells of S. rigidula, apical cells of Dictyota dichotoma, subapical cells of Choristocarpus tenellus, and meristematic cells of D. dichotoma (Figs. 1 and 2). In all cases it was found that a cortical AF system was present, always oriented parallel to the depositing MFs of the innermost wall layer (Katsaros et al., 2002). Although it is not possible to confirm the coincidence of AF-MF orientation using TEM, the mutual alignment between cortical AFs and MFs is a strong evidence that AFs are involved in cell wall morphogenesis of brown algae. To investigate further the above hypothesis, we disturbed actin cytoskeleton with cytochalasin B (CB) in order to ascertain whether MF deposition would be affected. Treatment of D. dichotoma thalli with 100 µg/ml CB for 24–36 h caused a gradual disruption of AFs. TEM examination of these cells showed that the MFs of the internal wall surface did not exhibit the clear transverse arrangement observed in normal cells. Instead, a rather random orientation of loose and thin MFs was found (Fig. 3). Misoriented MFs were also observed in CB treated cells of S. rigidula.
References Cyr RJ. Microtubules in plant morphogenesis: role of the cortical array. Ann Rev Cell Biol 1994;10:153–80. Fowler JE, Quatrano RS. Plant cell morphogenesis: plasma membrane interactions with the cytoskeleton and cell wall. Ann Rev Cell Dev Biol 1997;13:697–743. Karyophyllis D, Galatis B, Katsaros C. Centrosome and microtubule dynamics in apical cells of Sphacelaria rigidula (Phaeophyceae) treated with nocodazole. Protoplasma 1997;199:161–72. Karyophyllis D, Katsaros C, Dimitriadis I, Galatis B. F-actin organization during the cell cycle of Sphacelaria rigidula (Phaeophyceae). Eur J Phycol 2000a;35:25–33. Karyophyllis D, Katsaros C, Galatis B. F-actin involvement in apical cell morphogenesis of Sphacelaria rigidula (Phaeophyceae): mutual alignment between cortical actin filaments and cellulose microfibrils. Eur J Phycol 2000b;35:195–203. Katsaros C. Immunofluorescence study of microtubule organization in some polarized cell types of selected brown algae. Bot Acta 1992; 105:400–6. Katsaros C, Galatis B. Immunofluorescence and electron microscope studies of microtubule organization during the cell cycle of Dictyota dichotoma (Phaeophyta, Dictyotales). Protoplasma 1992; 169:75–84. Katsaros C, Galatis B, Mitrakos K. Fine structural studies on the interphase and dividing apical cells of Sphacelaria tribuloides (Phaeophyta). J Phycol 1983;19:16–30. Katsaros C, Karyophyllis D, Galatis B. Cortical F-actin underlies cellulose microfibril patterning in brown algal cells. Phycologia 2002;41:178–83. Mizuta S. Microtubules controlling cellulose deposition? A comparison between Chlorococcales and the giant green coenocytes. In: Menzel D, editor. The cytoskeleton of the algae. Boca Raton: CRC Press, 1992;149–63. Tsekos I. The sites of cellulose synthesis in algae: diversity and evolution of cellulose synthesizing enzyme complexes. J Phycol 1999;35:635–55.