Sporulation Competence in Physarum polycephalum CL and the Requirement for DNA Replication and Mitosis

Chapman, Aileen; Coote, J. G.

doi:10.1099/00221287-128-7-1489

Cited by 10 publications

(8 citation statements)

References 24 publications

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“…Microplasmodia of the white mutant strain LU897xLU898 (15) were cultured as described (16). Macroplasmodia were grown for 2 days and then starved (17). Induction was accomplished on the 4th day of starvation by a 3-hr illumination with fluorescent white light (Osram L40W/25-1; 2 W/m2, 220C).…”

Section: Methodsmentioning

confidence: 99%

Photomorphogenesis in Physarum: induction of tubulins and sporulation-specific proteins and of their mRNAs.

Putzer¹,

Verfuerth²,

Claviez³

et al. 1984

Proc. Natl. Acad. Sci. U.S.A.

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Sporangiophore formation in Physarum plasmodia starts about 10 hr after photoinduction. It is characterized by the induction of two tubulins and of at least 15 major sporangiophore morphogenetic proteins. In vitro translation of extracted mRNA revealed that differential gene expression is based on a highly synchronous temporal program of loss of plasmodial and induction of sporulation-specific mRNA species. Using a cloned cDNA encoding part of a sporangiophore morphogenetic protein from Physarum as a probe it was found that the induction of the complementary mRNA activity is due to the induction of the mRNA itself. The results suggest that light induces, with a lag phase of about 10 hr, the transient activation of sporulation-specific genes.Numerous developmental processes in microorganisms and plants are controlled by light (1-3). The mechanisms of signal transduction and differential gene expression during photomorphogenesis have been studied mainly in plant systems. The appearance of distinct mRNA species after induction by red or UV light in barley and in parsley suspension culture, respectively, is well established (4-7). According to the current hypothesis, light-induced gene expression in these systems is controlled at the transcriptional level (reviewed in ref. 8).The influence of light on gene expression in fungi and slime molds has been examined mostly at the level of inhibitor studies and overall RNA synthesis (1). We have chosen light-induced fruiting-body formation (sporulation) in plasmodia of the acellular slime mold Physarum polycephalum as a simple model system in which to study the expression of specific genes during light-induced development of a nonphotosynthetic organism. Sporulation in P. polycephalum is most effectively induced by UV/blue and red light (9, 10). Sporangiophore formation starts about 11 hr after the beginning of a 3-hr illumination period and is complete after about 20 hr. It includes a presporangial mitosis, cytoplasmic cleavage, and melanization of the sporangiophore heads (11, 12). Sporangiophore formation is sensitive to inhibitors of RNA and protein synthesis (12) and is accompanied by the synthesis of nonplasmodial RNA as well as of some spore-specific proteins (13,14). An unambiguous identification of these proteins, however, has not yet been achieved and nothing is known about the regulation of their expression during fruiting-body formation.Here we report that light induces a highly synchronous temporal program of mRNA regulation. Two of the photoinduced proteins were identified as tubulins. The cDNA of an unidentified sporangiophore morphogenetic protein (SMP) was cloned and used to demonstrate the induction of the corresponding mRNA sequences. MATERIALS AND METHODSCulture Conditions and Induction of Sporulation. Microplasmodia of the white mutant strain LU897xLU898 (15) were cultured as described (16). Macroplasmodia were grown for 2 days and then starved (17). Induction was accomplished on the 4th day of starvation by a 3-hr illumination with fluorescent ...

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Section: Methodsmentioning

confidence: 99%

Photomorphogenesis in Physarum: induction of tubulins and sporulation-specific proteins and of their mRNAs.

Putzer¹,

Verfuerth²,

Claviez³

et al. 1984

Proc. Natl. Acad. Sci. U.S.A.

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“…1G through I). By definition, plasmodia are regarded as competent if they sporulate within 16 to 24 h after light induction (2). The experiment shows that light is received by incompetent plasmodia and generates a photoreceptor signal which remains active for several days until morphogenesis finally occurs.…”

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confidence: 99%

Time-resolved detection of three intracellular signals controlling photomorphogenesis in Physarum polycephalum

Starostzik

Marwan

1994

J Bacteriol

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Incompetent plasmodia of Physarum polycephalum exposed to a light pulse sporulated after reaching the competent stage. Fusion of irradiated plasmodia with dark-incubated plasmodia and analysis of sporulation indicated the presence of a morphogenetic signal. It is concluded that a logic AND gate integrates the photoreceptor signal and the competence signal and controls the formation of the morphogenetic signal.

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“…The mechanism by which the plasmodium becomes competent to react to inducers of sporulation are poorly understood. However, starvation is a prerequisite for plasmodia to become competent to sporulate (4,7,17,18,22,26). Progress has been made in unraveling the perception of light by a starved plasmodium.…”

Section: Discussionmentioning

confidence: 99%

“…Progress has been made in unraveling the perception of light by a starved plasmodium. Three parallel pathways, triggered by either blue light, far-red light, or just heat shock, converge on a common photomorphogenesis pathway (4,13,14,18,23,24).…”

Section: Discussionmentioning

confidence: 99%

Calcium and Malate Are Sporulation-Promoting Factors ofPhysarum polycephalum

et al. 2000

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Fruiting body formation (sporulation) is a distinctive, irreversible differentiation process in the life cycle of the slime mold Physarum polycephalum. The most important requirement for sporulation of Physarum is a period of starvation, and normally sporulation proceeds in the light. It is shown here that by omitting the liquid sporulation medium and elevating the temperature from 21 to 25°C, sporulation can occur routinely in the dark. It is further shown that this autocrine signaling in the dark requires calcium ions and malate. A putative sporulation control factor was detected in conditioned media derived from plasmodia starved in the dark, which was then identified as polymalate. As an additional role for this previously detected polyanion, specific for the plasmodial state of Physarum, it is suggested that the secreted compound serves as a source for both malate and calcium ions and thus promotes sporulation without light signaling.Sporulation of Physarum polycephalum has long been considered a model system for the investigation of eukaryotic differentiation (7,18). During an extended starvation period of several days, the plasmodium reaches a state of "competence" (6) which enables it to activate a sporulation pathway after an induction signal, usually light, is perceived. This is followed by a "point of no return" (commitment), a morphogenetic sequence of multiheaded sporangia formation, hence the name P. polycephalum, and cellularization of uninucleate spores (17). Little is known about the biochemical events that establish the state of competence and promote sporulation. Wilkins and Reynolds demonstrated the existence of sporulation control factors (SCFs) (26). They suggested that starving plasmodia release these substances into the medium. A threshold level of the unidentified SCFs in the medium was postulated for acquiring competence to sporulate after illumination of a starved plasmodium.In this study, a new regimen to obtain sporulation in the light or in the dark has been established. It was used along with a solid matrix (agarose or agar) as a sensitive test for secretion of sporulation-promoting factors from the starved plasmodium and to assay active fractions obtained from conditioned medium. The same assay conditions were used to identify such activity among the components of the classical sporulation medium of Daniel and Rusch (6). We report here the involvement of three substances: calcium ions, malate, and polymalate. Calcium ions and malate are sufficient to promote sporulation in darkness; polymalate seems to be a sporulation control factor and may act as a source for calcium ions and malate. MATERIALS AND METHODSOrganism and culture media. Two lines of the yellow, haploid CL strain of Physarum polycephalum were investigated which differed in their sporulation potential. Strain CL-A, which had the lower sporulation potential (on average, 2 to 4 out of 10 cultures sporulated), was used as the acceptor for putative sporulation-promoting factors in "dark sporulation assays" (i.e., sporulati...

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Sporulation Competence in Physarum polycephalum CL and the Requirement for DNA Replication and Mitosis

Cited by 10 publications

References 24 publications

Photomorphogenesis in Physarum: induction of tubulins and sporulation-specific proteins and of their mRNAs.

Photomorphogenesis in Physarum: induction of tubulins and sporulation-specific proteins and of their mRNAs.

Time-resolved detection of three intracellular signals controlling photomorphogenesis in Physarum polycephalum

Calcium and Malate Are Sporulation-Promoting Factors ofPhysarum polycephalum

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