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Ca2+ influx and phosphoinositide signalling are essential for the establishment and maintenance of cell polarity in monospores from the red alga Porphyra yezoensis.

Li L, Saga N, Mikami K - J. Exp. Bot. (2009)

Bottom Line: The results indicate that the inhibition of the establishment of cell polarity, as judged by the ability of F-actin to localize asymmetrically, cell wall synthesis, and development into germlings, occurred when monospores were treated with inhibitors of the Ca2+ permeable channel, phospholipase C (PLC), diacylglycerol kinase, and inositol-1,4,5-trisphosphate receptor.Moreover, it was also found that light triggered the establishment of cell polarity via photosynthetic activity but not its direction, indicating that the Ca2+ influx and PLC activation required for the establishment of cell polarity are light dependent.Taken together, these findings suggest that there is functional diversity between the PLC and PLD signalling systems in terms of the formation of cell polarity; the former being critical for the light-dependent establishment of cell polarity and the latter playing a role in the maintenance of established cell polarity.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Fisheries Sciences, Hokkaido University, Hakodate 041-8611, Japan.

ABSTRACT
The asymmetrical distribution of F-actin directed by cell polarity has been observed during the migration of monospores from the red alga Porphyra yezoensis. The significance of Ca2+ influx and phosphoinositide signalling during the formation of cell polarity in migrating monospores was analysed pharmacologically. The results indicate that the inhibition of the establishment of cell polarity, as judged by the ability of F-actin to localize asymmetrically, cell wall synthesis, and development into germlings, occurred when monospores were treated with inhibitors of the Ca2+ permeable channel, phospholipase C (PLC), diacylglycerol kinase, and inositol-1,4,5-trisphosphate receptor. Moreover, it was also found that light triggered the establishment of cell polarity via photosynthetic activity but not its direction, indicating that the Ca2+ influx and PLC activation required for the establishment of cell polarity are light dependent. By contrast, inhibition of phospholipase D (PLD) prevented the migration of monospores but not the asymmetrical localization of F-actin. Taken together, these findings suggest that there is functional diversity between the PLC and PLD signalling systems in terms of the formation of cell polarity; the former being critical for the light-dependent establishment of cell polarity and the latter playing a role in the maintenance of established cell polarity.

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Involvement of PtdIns(4,5)P2 metabolites in the establishment of cell polarity in monospores. (A) Effects of 2-APB on the motility and development of monospores. Freshly released monospores incubated with an increasing concentration of 2-APB for 3 h (a) and 24 h (b). Columns and vertical bars represent the mean and SD, respectively (n=3). The organization of F-actin and renascent cell wall synthesis in 20 μM 2-APB treated monospores are indicated in (c) and (d), respectively. Upper and lower photographs in each panel show bright-field and fluorescent images, respectively. Scale bars=5 μm. (B) Effects of R59022 on the motility and development of monospores. Freshly released monospores incubated with an increasing concentration of R59022 for 3 h (a) and 24 h (b). Columns and vertical bars represent the mean and SD, respectively (n=3). The organization of F-actin and renascent cell wall synthesis in 15 μM R59022 treated monospores are indicated in (c) and (d), respectively. Upper and lower photographs in each panel show bright-field and fluorescent images, respectively. Scale bars=5 μm.
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fig3: Involvement of PtdIns(4,5)P2 metabolites in the establishment of cell polarity in monospores. (A) Effects of 2-APB on the motility and development of monospores. Freshly released monospores incubated with an increasing concentration of 2-APB for 3 h (a) and 24 h (b). Columns and vertical bars represent the mean and SD, respectively (n=3). The organization of F-actin and renascent cell wall synthesis in 20 μM 2-APB treated monospores are indicated in (c) and (d), respectively. Upper and lower photographs in each panel show bright-field and fluorescent images, respectively. Scale bars=5 μm. (B) Effects of R59022 on the motility and development of monospores. Freshly released monospores incubated with an increasing concentration of R59022 for 3 h (a) and 24 h (b). Columns and vertical bars represent the mean and SD, respectively (n=3). The organization of F-actin and renascent cell wall synthesis in 15 μM R59022 treated monospores are indicated in (c) and (d), respectively. Upper and lower photographs in each panel show bright-field and fluorescent images, respectively. Scale bars=5 μm.

Mentions: PLC hydrolyses PtdIns(4,5)P2 into two second messengers, IP3 and DG (Katan, 1998). Since it was recently shown that IP3R exists in green algae (Wheeler and Brownlee, 2008), it was also examined whether IP3R-like activity is required for the early development of monospores using an IP3R antagonist, 2-APB, which inhibits IP3R activity on the ER membrane in animal cells (Maruyama et al., 1997). Treatment of monospores with 2-APB prevented the migration of monospores but no difference was observed with a concentration ranging from 5 μM to 20 μM (Fig. 3Aa). In addition, inhibition of germling development was observed in a dose-dependent manner (Fig. 3Ab). When freshly released monospores were treated with 20 μM 2-APB for 3 h, symmetrical distribution of F-actin and cell wall-free monospores were observed in erratic monospores without amoeboid movement (Fig. 3Ac, d). After 24 h incubation, monospores returned to a spherical shape or remained grotesque until death (data not shown). These effects were recovered following 2-APB removal (data not shown). However, since specificity of 2-APB for IP3R is not high, further experiments are needed to confirm the presence of IP3R in P. yezoensis.


Ca2+ influx and phosphoinositide signalling are essential for the establishment and maintenance of cell polarity in monospores from the red alga Porphyra yezoensis.

Li L, Saga N, Mikami K - J. Exp. Bot. (2009)

Involvement of PtdIns(4,5)P2 metabolites in the establishment of cell polarity in monospores. (A) Effects of 2-APB on the motility and development of monospores. Freshly released monospores incubated with an increasing concentration of 2-APB for 3 h (a) and 24 h (b). Columns and vertical bars represent the mean and SD, respectively (n=3). The organization of F-actin and renascent cell wall synthesis in 20 μM 2-APB treated monospores are indicated in (c) and (d), respectively. Upper and lower photographs in each panel show bright-field and fluorescent images, respectively. Scale bars=5 μm. (B) Effects of R59022 on the motility and development of monospores. Freshly released monospores incubated with an increasing concentration of R59022 for 3 h (a) and 24 h (b). Columns and vertical bars represent the mean and SD, respectively (n=3). The organization of F-actin and renascent cell wall synthesis in 15 μM R59022 treated monospores are indicated in (c) and (d), respectively. Upper and lower photographs in each panel show bright-field and fluorescent images, respectively. Scale bars=5 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
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fig3: Involvement of PtdIns(4,5)P2 metabolites in the establishment of cell polarity in monospores. (A) Effects of 2-APB on the motility and development of monospores. Freshly released monospores incubated with an increasing concentration of 2-APB for 3 h (a) and 24 h (b). Columns and vertical bars represent the mean and SD, respectively (n=3). The organization of F-actin and renascent cell wall synthesis in 20 μM 2-APB treated monospores are indicated in (c) and (d), respectively. Upper and lower photographs in each panel show bright-field and fluorescent images, respectively. Scale bars=5 μm. (B) Effects of R59022 on the motility and development of monospores. Freshly released monospores incubated with an increasing concentration of R59022 for 3 h (a) and 24 h (b). Columns and vertical bars represent the mean and SD, respectively (n=3). The organization of F-actin and renascent cell wall synthesis in 15 μM R59022 treated monospores are indicated in (c) and (d), respectively. Upper and lower photographs in each panel show bright-field and fluorescent images, respectively. Scale bars=5 μm.
Mentions: PLC hydrolyses PtdIns(4,5)P2 into two second messengers, IP3 and DG (Katan, 1998). Since it was recently shown that IP3R exists in green algae (Wheeler and Brownlee, 2008), it was also examined whether IP3R-like activity is required for the early development of monospores using an IP3R antagonist, 2-APB, which inhibits IP3R activity on the ER membrane in animal cells (Maruyama et al., 1997). Treatment of monospores with 2-APB prevented the migration of monospores but no difference was observed with a concentration ranging from 5 μM to 20 μM (Fig. 3Aa). In addition, inhibition of germling development was observed in a dose-dependent manner (Fig. 3Ab). When freshly released monospores were treated with 20 μM 2-APB for 3 h, symmetrical distribution of F-actin and cell wall-free monospores were observed in erratic monospores without amoeboid movement (Fig. 3Ac, d). After 24 h incubation, monospores returned to a spherical shape or remained grotesque until death (data not shown). These effects were recovered following 2-APB removal (data not shown). However, since specificity of 2-APB for IP3R is not high, further experiments are needed to confirm the presence of IP3R in P. yezoensis.

Bottom Line: The results indicate that the inhibition of the establishment of cell polarity, as judged by the ability of F-actin to localize asymmetrically, cell wall synthesis, and development into germlings, occurred when monospores were treated with inhibitors of the Ca2+ permeable channel, phospholipase C (PLC), diacylglycerol kinase, and inositol-1,4,5-trisphosphate receptor.Moreover, it was also found that light triggered the establishment of cell polarity via photosynthetic activity but not its direction, indicating that the Ca2+ influx and PLC activation required for the establishment of cell polarity are light dependent.Taken together, these findings suggest that there is functional diversity between the PLC and PLD signalling systems in terms of the formation of cell polarity; the former being critical for the light-dependent establishment of cell polarity and the latter playing a role in the maintenance of established cell polarity.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Fisheries Sciences, Hokkaido University, Hakodate 041-8611, Japan.

ABSTRACT
The asymmetrical distribution of F-actin directed by cell polarity has been observed during the migration of monospores from the red alga Porphyra yezoensis. The significance of Ca2+ influx and phosphoinositide signalling during the formation of cell polarity in migrating monospores was analysed pharmacologically. The results indicate that the inhibition of the establishment of cell polarity, as judged by the ability of F-actin to localize asymmetrically, cell wall synthesis, and development into germlings, occurred when monospores were treated with inhibitors of the Ca2+ permeable channel, phospholipase C (PLC), diacylglycerol kinase, and inositol-1,4,5-trisphosphate receptor. Moreover, it was also found that light triggered the establishment of cell polarity via photosynthetic activity but not its direction, indicating that the Ca2+ influx and PLC activation required for the establishment of cell polarity are light dependent. By contrast, inhibition of phospholipase D (PLD) prevented the migration of monospores but not the asymmetrical localization of F-actin. Taken together, these findings suggest that there is functional diversity between the PLC and PLD signalling systems in terms of the formation of cell polarity; the former being critical for the light-dependent establishment of cell polarity and the latter playing a role in the maintenance of established cell polarity.

Show MeSH