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Evidence for a plasma membrane mating receptor in the myxomycete Didymium iridis
1Department of Biology, Youngstown State University, Ohio 44555.
Abstract:
Haploid isolates Panamanian 2-7A8 and Honduran 1-2A1 of the heterothallic myxomycete Didymium iridis were investigated in order to determine whether membrane mating factors or receptors were present and necessary in order that cell fusion could occur and zygote formation take place. Haploid and diploid controls grown on half strength cornmeal media, and experimental crosses grown on the same media plus concanavalin A, were analysed by quantitative cytophotometry employing the Feulgen nuclear reaction. Nuclear DNA analysis demonstrated that Con A treated cells when crossed did not produce zygotes or plasmodia, while those left untreated did so almost all of the time. On rare occasion plasmodia did develop in treated cultures (1.8% or two out of 110). These plasmodia demonstrated low viability and upon analysis were shown to be haploid. It was concluded that they had developed by apogamy, and therefore did not require plasma membrane bound mating receptors, cell fusion, or zygote formation.
Insights
Concanavalin A (Con A) inhibits mating in Didymium iridis by preventing cell fusion and zygote formation. Apogamy, a form of asexual reproduction, occurred in rare Con A-treated cultures.
Area of Science:
- Mycology
- Cell Biology
- Genetics
Background:
- The heterothallic myxomycete Didymium iridis relies on cell fusion for sexual reproduction.
- Understanding the role of membrane-bound factors in mating is crucial for myxomycete sexual reproduction.
Purpose of the Study:
- To investigate the necessity of membrane mating factors and receptors for cell fusion and zygote formation in Didymium iridis.
- To determine the effect of concanavalin A (Con A) on mating and zygote development.
Main Methods:
- Quantitative cytophotometry using the Feulgen nuclear reaction was employed.
- Haploid and diploid isolates of Didymium iridis were cultured on cornmeal media.
- Experimental crosses were treated with concanavalin A (Con A) to assess its impact on mating.
Main Results:
- Con A treatment significantly inhibited zygote and plasmodia formation in experimental crosses.
- Untreated crosses consistently formed zygotes and plasmodia.
- Rare plasmodia in Con A-treated cultures were haploid, viable, and developed via apogamy.
Conclusions:
- Plasma membrane-bound mating receptors and cell fusion are essential for zygote formation in Didymium iridis.
- Con A effectively blocks the mating process, suggesting its interference with membrane interactions.
- Apogamy can occur in the absence of cell fusion and zygote formation, bypassing the need for mating receptors.