Volume 16 Part 1 Article 13: Molecular Analysis of Breeding Behavior in Agaricus Species

Volume 16 Part 1 Article 13
Year 2004
Title: Molecular Analysis of Breeding Behavior in Agaricus Species
Authors: Y. Li, M. Challen, T. Elliott and L. Casselton


Agaricus species exhibit a range of breeding life-styles. Within the A. bisporus group, there are individuals that are typically heterothallic (self-sterile) as well as those that are truly homothallic (selffertile). We are characterizing mating type genes from isolates within A. bisporus and among other Agaricus species to study the role and function of these genes in the evolution of different breeding behaviors. In the two-spored cultivated A. bisporus, the unifactorial A mating type locus determines mating compatibility. Haploid nuclei of opposite mating type are partitioned into each of the two spores that germinate, to form a fertile heterokaryon (secondarily homothallism). Wild, four-spored varieties of A. bisporus exhibit more conventional heterothallic behavior where meiotic nuclei are individually compartmentalized; non-self-fertile homokaryons must fuse with compatible partners to generate fertile heterokaryons. Other Agaricus species may be truly self-fertile and do not need to mate. We have identified and sequence characterized a pair of divergently transcribed homeobox genes within the mating type locus of A. bisporus. PCR strategies have been used to identify allelic variants in different A specificities. These analyses aim to reveal whether a single pair of genes is sufficient to generate the allelic variation displayed in the wild collections of A. bisporus. Work is in progress to clone mating type genes from the heterothallic A. bitorquis and homothallic A. subfloccosus.

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