Variations in macronuclear chromatin structure andchromatin extrusion in excystment from resting cysts of Colpoda inflata

Chessa, Maria Giovanna; Gallus, Lorenzo; Tiano, Luca; Trielli, Francesca; Corrado, Maria Umberta Delmonte

doi:10.1078/0932-4739-00825

Cited by 5 publications

(6 citation statements)

References 11 publications

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“…This development implies that the macronucleus is transcriptionally active during early excystment. In line with this assumption, Chessa et al (2001) studied, by image analysis, the macronucleus of Colpoda inflata to determine variations that occur in chromatin structure during excystment from resting cysts. A comparative morphometric and densiometric analysis was performed on macronuclei of differently aged cysts: from 1-day-old cysts to 1-year-old cysts.…”

Section: Excystmentmentioning

confidence: 99%

Resting cysts: A survival strategy in Protozoa Ciliophora

Verni

Rosati

2011

Italian Journal of Zoology

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Encystment is a reversible cell differentiation process that also requires an antagonistic process, i.e. excystment. Both processes are genetically encoded. Encystment is of common occurrence among free-living ciliates and may serve several different purposes. In some ciliates, this process is part of the regular life cycle (reproductive cyst), while many other ciliates undergo encystment when environmental conditions become adverse (resting cyst). In this review, the different phases and aspects of the encystment process in ciliates, such as the ecological role, the cyst formation, the morphological characteristics of the cysts and their dynamic state during the time and the excysting process are reviewed on the basis on our own results and literature data.

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Section: Excystmentmentioning

confidence: 99%

Resting cysts: A survival strategy in Protozoa Ciliophora

Verni

Rosati

2011

Italian Journal of Zoology

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“…Conjugation in ciliates is a process that is associated with rejuvenation via the replacement of the parental macronucleus by the new zygotic macronucleus (Miwa, 1973). Unlike a majority of ciliates, some species such as Colpoda lack conjugation; therefore, it has been generally believed that chromatin extrusion serves as a mechanism for rejuvenation by excluding damaged DNA from the macronucleus during encystment instead of conjugation (Tiano et al, 1999;Chessa et al, 2001). However, we failed to confirm this hypothesis, since no increase in the frequency of CE in older cells (in terms of clonal aging after excystment) was observed (Fig.…”

Section: Discussionmentioning

confidence: 66%

“…Chessa and Delmonte Corrado (1994) showed that DNA synthesis occurred in the earliest phase of encystment in starved Colpoda inflata. They also showed that chromatin extrusion does not involve DNA synthesis (Chessa et al, 2001). It is likely that growing cells of Colpoda regulate extra macronuclear DNA content downward by extruding chromatin, while starved cells synthesize DNA in the encystment process (Chessa and Delmonte Corrado, 1994).…”

Section: Discussionmentioning

confidence: 99%

“…Previous reports have suggested that CE is associated with agamic cell rejuvenation (Tiano et al, 1999;Chessa et al, 2001). If this is the case, CE should occur more frequently in aged cells rather than younger cells, and cell senescence should be a prerequisite for the induction of CE at high frequencies.…”

Section: Experimental Induction Of Cementioning

confidence: 93%

“…Resting encystment of C. cucullus can be experimentally induced by an increased concentration of divalent cations such as Ca 2þ in the surrounding medium; such an increased concentration signals for the forthcoming desiccation (Yamaoka et al, 2004). Tiano et al (1999) and Chessa et al (2001) proposed the idea that resting encystment of Colpoda would give rise to rejuvenated cell lines, since preventing resting encystment resulted in a decrease of the fission rate. However, this rate was recovered in excysted cell lines to the same extent that it was recovered in young cells (Franceschi Crippa, 1967;Pelli et al, 1997).…”

Section: Introductionmentioning

confidence: 99%

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Chromatin extrusion in resting encystment of Colpoda cucullus: A possible involvement of apoptosis‐like nuclear death

Akematsu¹,

Matsuoka²

2008

Cell Biology International

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The extrusion of macronuclear chromatin is a remarkable characteristic during encystment in Colpoda, but the biological significance of this phenomenon has not been fully elucidated. Here we demonstrate that chromatin extrusion occurs with high frequency when encystment was induced by increasing Ca(2+) in growing cells in various stages of the cell cycle. The Feulgen-DNA reaction revealed that vegetatively growing cells have more macronuclear DNA than cells in the stationary phase, suggesting an association of macronuclear DNA content with the execution of chromatin extrusion. Using 4',6-diamidino-2-phenylindole (DAPI), we found that the size of the macronuclear extrusion body was reduced with time and eventually disappeared approximately 24h after encystment induction. In addition, oligonucleosome-sized DNA cleavage was confirmed to occur concomitant with the size reduction, suggesting that the extrusion body is selectively degraded, while the normal macronucleus remains alive. Combined use of acridine orange and Hoechst 33342 demonstrated that the extruded body was increasingly acidified before final resorption. These features are reminiscent of the nuclear degradation process in conjugating Tetrahymena, and therefore we conclude that chromatin extrusion in Colpoda might occur to adjust the macronuclear DNA content prior to encystment. In this way, it is similar to the apoptotic-like nuclear death that occurs during the conjugation of other ciliates.

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