Heterothallism Vs Homothallism

The processes leading to fertilization and production of progeny are quite variable in fungi. In the early twentieth century, A.F. Blakeslee found that a large number of morphologically indistinguishable single spore-derived cultures of a species belonging to Mucorales (Zygomycotina) could be sorted into two types, which he called "plus" (+) and "minus" (-) since the strains could not be morphologically distinguished as male or female. If a "plus" colony was grown with another "plus" strain in a petri dish, or if a "minus" strain with another "minus" strain, there was no reaction. However, if the "plus" and the "minus" strains encountered each other, a line of sexually formed spores called zygospores formed in the zone of contact. The term heterothallism is used to designate when there is the occurrence within a given species of two kinds of individuals, each self-sterile. In this situation, intermycelial reaction is required for sexual fusion, irrespective of the presence or absence of differentiated gametangia (Figure 8.1). From this discovery arose the concept that genes control the mating types. The mating types of strains are designated as AJa as in Neurospora crassa (Chapter 5) or a/a in Saccharomyces cerevisiae (Chapter 6) to indicate that the differences between the strains are due to two alleles of a single gene.

Conversely, the term homothallism is used when a single individual that originates from a single spore forms morphologically similar male and female gametangia and is able to complete sexual cycle, i.e., it is self-fertile and sexually self-sufficient. For example, in the homothallic fungus Rhizopus sexualis (Zygomycotina), neighboring hyphal branches of the same individual form gametangia that fuse (Figure 8.2). Here, sexual fusion occurs between

Heterothallism Homothallism
Figure 8.1 Sexual reproduction in heterothallic Mucor hiemalis showing mating of morphologically similar cells from two individuals (designated plus and minus) to form zygospore. (From Ingold, C.T. (1961), The Biology of Fungi. Chapman and Hall. With permission from Kluwer Academic Publishers.)

cells containing genetically identical (sister) nuclei. Note that although they do not seek a mate, the homothallic fungi still engage in sexual reproduction, retaining karyogamy and meiosis. Since rapid propagation of these fungi can also occur vegetatively, how homothallic fungus benefits from the two processes of karyogamy and meiosis is a puzzling question.

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Responses

  • elizabeth
    What is the concept of homothallism and heterothallism?
    4 years ago
  • dawit
    What is homothalism and heterothalism?
    4 years ago
  • PRISCO BRUNO
    What is the difference of homothallic from heterothallic?
    4 years ago
  • Maria Rosa
    What is homothalism in fungi?
    4 years ago
  • tewolde
    What is the difference btw homothalism and hermaphroditic in fungi?
    4 years ago
  • Caren
    Do heterothallic or homothallic fungi reproduce more?
    4 years ago
  • erno
    Who coined theb term homothalism and heterothalli?
    10 months ago
  • stefan
    Who discovered homothallism?
    6 months ago
  • Amaranth
    What is the difference between homthallic fungi & heterothallic fungi?
    4 months ago
  • Uta
    What is difference between homo thallism and heterothallism?
    4 months ago
  • ANDREA
    What is homothalism or heterothallism?
    3 months ago
  • ulrich
    What is difference between homothalic and heterothalic fungi?
    3 months ago

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