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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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Calcium influx plays an important role in the establishment of cell polarity in monospores. (A) The polarized F-actin and renascent cell wall synthesis in monospores incubated in ESL for 3 h after release from the gametophyte. The polarized F-actin accumulated in the front of the migrating monospores (a) and the renascent cell wall synthesis in migrating monospores (b). The arrow in (a) indicates the direction of migration of the monospore. Left and right photographs in each panel show bright-field and fluorescent images, respectively. Scale bars=5 μm. (B) Effects of calcium chelator (EGTA) and calcium channel blocker (LaCl3) on the F-actin organization and renascent cell wall synthesis. Freshly released monospores incubated with 1 mM EGTA (a, b) and 100 μM LaCl3 (c, d) for 3 h, which indicate the symmetrical organization of F-actin (a, c) and no renascent cell wall synthesis (b, d). Upper and lower photographs in each panel show bright-field and fluorescent images, respectively. Scale bars=5 μm. (C) Dose-dependent inhibition of the motility and development of monospores by calcium chelator and channel blocker. Freshly released monospores incubated with an increasing concentration of EGTA (a, c) and LaCl3 (b, d) for 3 h (a, b) and 24 h (c, d). Columns and vertical bars represent the mean and SD, respectively (n=3).
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fig1: Calcium influx plays an important role in the establishment of cell polarity in monospores. (A) The polarized F-actin and renascent cell wall synthesis in monospores incubated in ESL for 3 h after release from the gametophyte. The polarized F-actin accumulated in the front of the migrating monospores (a) and the renascent cell wall synthesis in migrating monospores (b). The arrow in (a) indicates the direction of migration of the monospore. Left and right photographs in each panel show bright-field and fluorescent images, respectively. Scale bars=5 μm. (B) Effects of calcium chelator (EGTA) and calcium channel blocker (LaCl3) on the F-actin organization and renascent cell wall synthesis. Freshly released monospores incubated with 1 mM EGTA (a, b) and 100 μM LaCl3 (c, d) for 3 h, which indicate the symmetrical organization of F-actin (a, c) and no renascent cell wall synthesis (b, d). Upper and lower photographs in each panel show bright-field and fluorescent images, respectively. Scale bars=5 μm. (C) Dose-dependent inhibition of the motility and development of monospores by calcium chelator and channel blocker. Freshly released monospores incubated with an increasing concentration of EGTA (a, c) and LaCl3 (b, d) for 3 h (a, b) and 24 h (c, d). Columns and vertical bars represent the mean and SD, respectively (n=3).

Mentions: As previously reported (Li et al., 2008), migration of monospores required the pre-establishment of cell polarity for the asymmetrical localization of F-actin on the front side of migrating cells (Fig. 1Aa); this followed the synthesis of renascent cell wall during migration (Fig. 1Ab). The factors involved in the formation of cell polarity in monospores, as judged by the localization of F-actin and cell wall synthesis, are investigated further here. It was evident when F-actin was observed that treatment with phalloidin had resulted in monospore frangibility and a change in colour of the red chloroplasts to pale or green; the monospores were weakened to the extent that they could not bear the weight of the cover glass. In addition, crushing of the monospores into a flat shape by the weight of the cover-glass sometimes produced autofluorescence from the chloroplasts. However, phalloidin treatment itself did not affect the organization of F-actin and the images of F-actin that correctly exhibited the effect of the inhibitors used in this study. Fluorescent Brightener 28 treatment for the visualization of the cell wall did not create such a problem.


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)

Calcium influx plays an important role in the establishment of cell polarity in monospores. (A) The polarized F-actin and renascent cell wall synthesis in monospores incubated in ESL for 3 h after release from the gametophyte. The polarized F-actin accumulated in the front of the migrating monospores (a) and the renascent cell wall synthesis in migrating monospores (b). The arrow in (a) indicates the direction of migration of the monospore. Left and right photographs in each panel show bright-field and fluorescent images, respectively. Scale bars=5 μm. (B) Effects of calcium chelator (EGTA) and calcium channel blocker (LaCl3) on the F-actin organization and renascent cell wall synthesis. Freshly released monospores incubated with 1 mM EGTA (a, b) and 100 μM LaCl3 (c, d) for 3 h, which indicate the symmetrical organization of F-actin (a, c) and no renascent cell wall synthesis (b, d). Upper and lower photographs in each panel show bright-field and fluorescent images, respectively. Scale bars=5 μm. (C) Dose-dependent inhibition of the motility and development of monospores by calcium chelator and channel blocker. Freshly released monospores incubated with an increasing concentration of EGTA (a, c) and LaCl3 (b, d) for 3 h (a, b) and 24 h (c, d). Columns and vertical bars represent the mean and SD, respectively (n=3).
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2724695&req=5

fig1: Calcium influx plays an important role in the establishment of cell polarity in monospores. (A) The polarized F-actin and renascent cell wall synthesis in monospores incubated in ESL for 3 h after release from the gametophyte. The polarized F-actin accumulated in the front of the migrating monospores (a) and the renascent cell wall synthesis in migrating monospores (b). The arrow in (a) indicates the direction of migration of the monospore. Left and right photographs in each panel show bright-field and fluorescent images, respectively. Scale bars=5 μm. (B) Effects of calcium chelator (EGTA) and calcium channel blocker (LaCl3) on the F-actin organization and renascent cell wall synthesis. Freshly released monospores incubated with 1 mM EGTA (a, b) and 100 μM LaCl3 (c, d) for 3 h, which indicate the symmetrical organization of F-actin (a, c) and no renascent cell wall synthesis (b, d). Upper and lower photographs in each panel show bright-field and fluorescent images, respectively. Scale bars=5 μm. (C) Dose-dependent inhibition of the motility and development of monospores by calcium chelator and channel blocker. Freshly released monospores incubated with an increasing concentration of EGTA (a, c) and LaCl3 (b, d) for 3 h (a, b) and 24 h (c, d). Columns and vertical bars represent the mean and SD, respectively (n=3).
Mentions: As previously reported (Li et al., 2008), migration of monospores required the pre-establishment of cell polarity for the asymmetrical localization of F-actin on the front side of migrating cells (Fig. 1Aa); this followed the synthesis of renascent cell wall during migration (Fig. 1Ab). The factors involved in the formation of cell polarity in monospores, as judged by the localization of F-actin and cell wall synthesis, are investigated further here. It was evident when F-actin was observed that treatment with phalloidin had resulted in monospore frangibility and a change in colour of the red chloroplasts to pale or green; the monospores were weakened to the extent that they could not bear the weight of the cover glass. In addition, crushing of the monospores into a flat shape by the weight of the cover-glass sometimes produced autofluorescence from the chloroplasts. However, phalloidin treatment itself did not affect the organization of F-actin and the images of F-actin that correctly exhibited the effect of the inhibitors used in this study. Fluorescent Brightener 28 treatment for the visualization of the cell wall did not create such a problem.

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