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United States Department of Agriculture

Agricultural Research Service

Research Project: IMPROVEMENT OF HARD RED SPRING AND DURUM WHEAT FOR DISEASE RESISTANCE AND QUALITY USING GENETICS AND GENOMICS

Location: Cereal Crops Research

Title: Tracing the Origin of the fungal Sex a1 domain places its ancestor in the HMG-box superfamily: implication for fungal mating-type evolution

Authors
item Martin, Tom -
item Lu, Shunwen
item Tilbeurgh, Herman -
item Ripoll, Daniel -
item Dixelius, Christina -
item Turgeon, B -
item Debuchy, Robert -

Submitted to: PLoS One
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 29, 2010
Publication Date: December 8, 2010
Citation: Martin, T., Lu, S., Tilbeurgh, H., Ripoll, D., Dixelius, C., Turgeon, B.G., Debuchy, R. 2010. Tracing the Origin of the fungal Sex a1 domain places its ancestor in the HMG-box superfamily: implication for fungal mating-type evolution. PLoS One. 5(12):e15199.

Interpretive Summary: Many species of fungi in Pezizomycotina (filamentous ascomycetes) are heterothallic (self-incompatible), i.e., a sexual recombination (mating) occurs only between two individuals that have opposite mating types. Mating type is controlled by the mating-type locus (MAT) which is characterized by two alternative sequences occupying the same locus on corresponding chromosomes. One sequence is characterized by a gene encoding a protein belonging to the high mobility group (HMG), while the hallmark of the other is a gene encoding a protein with an a1-box domain showing similarity to the a1 protein of Saccharomyces cerevisiae. While both HMG and a1-box domains are DNA-binding-related, the former is ubiquitous and well characterized, and the later is found only in fungi and has not been placed in any of the large families of sequence-specific DNA-binding proteins. The objective of this study was to understand mating-type evolution by comparative, phylogenetic and in silico analyses of the amino acid sequences of the MAT-encoded HMG and a1-box domains. The results suggested that the a1 domain is related to the HMG domain. Our analyses have also identified a new motif termed HMG related (HMGR) in the a1 proteins that is conserved in Pezizomycotina. We propose a model for fungal mating-type evolution, based on the assumption that extant a1-box genes originated from an ancestral HMG gene. This study provided new insights into the mating-type evolution in Ascomycota.

Technical Abstract: Fungal mating types in self-incompatible Pezizomycotina are specified by one of two alternate sequences occupying the same locus on corresponding chromosomes. One sequence is characterized by a gene encoding an HMG protein, while the hallmark of the other is a gene encoding a protein with an a1 domain showing similarity to the a1 protein of Saccharomyces cerevisiae. DNA-binding HMG proteins are ubiquitous and well characterized. In contrast, a1 domain proteins have limited distribution and their evolutionary origin is obscure, precluding a complete understanding of mating-type evolution in Ascomycota. Although much work has focused on the role of the S. cerevisiae a1 protein as a transcription factor, it has not yet been placed in any of the large families of sequence-specific DNA-binding proteins. We present sequence comparisons, phylogenetic analyses, and in silico predictions of secondary and tertiary structures, which support our hypothesis that the a1 domain is related to the HMG domain. We have also characterized a new conserved motif in a1 proteins of Pezizomycotina, termed HMG related (HMGR). We propose a model for fungal mating-type evolution, based on the assumption that extant a1-box genes originated from an ancestral HMG gene.

Last Modified: 4/20/2014
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