Cloning and characterization of mating type A locus in Ganoderma lucidum
Date Issued
2008
Date
2008
Author(s)
Yuan, Ju-Ling
Abstract
Ganoderma lucidum is a potent medicinal fungi and convinced to be beneficial to health. We use Ganoderma lucidum as model organism to study mating loci gene. In our previous studies, 4 A mating type genes and 39 B mating type genes were characterized in four different Ganoderma lucidum mating types (A1B1, A2B2, A1B2, A2B2, respectively). In order to further characterize the A mating type locus in Ganoderma lucidum, genomic DNA was digested with HindIII and hybridized with 4 probes of A mating type genes, a1, a2, b1, and b2. The results indicate that a1 and a2 are single copy and localized in only A1 mating type locus, whereas b1 and b2 in the A2 mating type locus. Fosmid library clones are hybridized with the same probes, and the clones harboring the A1 and A2 mating type genes were shotgun sequenced. The contigs of genomic region containg A1 and A2 loci genes were further connected and extended with two other overlap fosmids to work out the full length of 93 kb A1 locus and 99 kb A2 locus, each locus except the mating type genes contains 18 conserved genes and 6 or 8 hypothetical genes, respectively. Synteny comparison between the two loci in G. lucidum, and also A loci in other five Agaricomycetes were performed. According to the synteny map, six species can be separated into two groups, the Aphyllophorales and the Agaricales. RACE (Rapid Amplification of cDNA Ends) was performed to characterize the full length of both b1 and b2 cDNA. We found that alternative splicing events take place in A mating type genes, which results in different isoforms. One a1 isoform, two a2 isoforms, four b1 isoforms, and two b2 isoforms were cloned. The helical regions which participate in heterodimerization between different A locus genes were predicted at the N-terminal of a1, a2, b1, and b2. a1 and b1 proteins are extremely variable compared to HD1 genes from other basidiomycetes, including the homeodomain region. Neverthless, a2 and b2 proteins are very conserved in homeodomain, and a N-terminal mTP (mitochondrial targeting peptide) was predicted in both protein, which may target a2 and b2 protein to mitochondria. Since many protein in A locus were targeted to mitichondria, their possible functions other than mating type determination and recognition were also discussed.
Subjects
Ganoderma lucidum
mating type
mating type locus
mating type gene
synteny
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