Structures of the Mating-Type Loci of Cordyceps takaomontana

Abstract

Nucleotide sequences of the mating-type loci MAT1-1 and MAT1-2 of Cordyceps takaomontana were determined, which is the first such report for the clavicipitaceous fungi. MAT1-1 contains two mating-type genes, MAT1-1-1 and MAT1-1-2, but MAT1-1-3 could not be found. On the other hand, MAT1-2 has MAT1-2-1. A pseudogene of MAT1-1-1 is located next to MAT1-2.Entomopathogenic fungus Paecilomyces tenuipes is an anamorph of Cordyceps takaomontana (Ascomycota: Pyrenomycetes: Hypocreales [Clavicipitales]: Clavicipitaceae [15]). We use the holomorphic name C. takaomontana for P. tenuipes in this report. C. takaomontana has been used as a traditional medicine in Korea. Clavicipitaceous fungi are the potential sources for medicines such as ergot alkaloids from Claviceps purpurea, cordycepin from Cordyceps sinensis, and cyclosporine from Tolypocladium inflatum. C. takaomontana is also a source of bioactive compounds such as 4-acetyl-12,13-epoxyl-9-trichothecene-3, 15-diol (12). But the difficulties involved in artificially producing fruiting bodies such as perithecioid ascomata and synnemata hinder their usefulness. The analysis of mating type will shed light on the mating mechanisms and on the anamorph-teleomorph connection.Recently the mating-type loci have been analyzed, mainly in the phytopathogenic fungi belonging to Discomycetes, Loculoascomycetes,8,[17][18][19]. The mating types MAT1 and MAT2 are determined by the single matingtype locus MAT1. Alleles for MAT1 and MAT2 are MAT1-1 and MAT1-2, respectively. Although the flanking regions of MAT1-1 and MAT1-2 are homologous, the nucleotide sequences of MAT1-1 and MAT1-2 are highly dissimilar. The term "idiomorph" is usually used instead of "allele" for MAT1-1 and MAT1-2. Heterothallic fungi have one of the idiomorphs MAT1-1 and MAT1-2. On the other hand, most of the homothallic fungi, except for some Neurospora species (6), have both idiomorphs.The mating system of C. takaomontana is unknown; we determined the nucleotide sequences of the mating-type loci to investigate the molecular background of its mating system. Fungal strains. A total of 22 isolates (BCMU IJ01 to IJ09, IJ11, IJ13 to IJ18, and IJ20 to IJ25) of C. takaomontana were obtained from the synnemata formed on the 22 lepidopteran pupae, which were collected at the Prefecture of Aichi in Japan. The nucleotide sequences of the 18S ribosomal DNA of all C. takaomontana isolates were determined. The phylogenetic analysis based on the nucleotide sequences of 18S ribosomal DNA was done using the neighbor-joining method (13).These isolates were closely related to C. takaomontana (accession numbers AB044631 [11] and AB070372 [21]) and formed a monophyly supported by a 97.7% bootstrap value. C. takaomontana IFO 31161, which had been isolated at the Prefecture of Nara in Japan, was purchased from the Institute for Fermentation, Osaka (Japan).Mating-type locus MAT1-2. The HMG box of MAT1-2-1 is most conserved among the mating-type gene products of MAT1-1 and MAT1-2. MAT1-2-1 protein belongs to the TCF/ SOX family (9) of the ...

Sex in Penicillium: Combined phylogenetic and experimental approaches

“…These results are also consistent with other studies in fungi: in almost all the putatively asexual species where mating type genes have been sequenced, they presented no evidence of loss-of-function mutations (O'Donnell et al, 2004). Only in the entomopathogenic fungus Cordyceps takaomontana did mating type loci contain pseudogenes (Yokoyama et al, 2003). This suggests that in most fungi, mating type genes may still be functional, which is not expected if these species were truly asexual for long.…”

Characterization of the mating-type genes in Leptographium procerum and Leptographium profanum

“…We were also able to identify (Coppin et al 1997;Turgeon and Yoder 2000). However, similar structures have also been observed in the MAT1-2 idiomorphs of few other heterothallic Sordariomycetes, where pseudogenes, partial sequences, or homologs of MAT1-1 genes are present in the MAT1-2 idiomorph (Kanematsu et al 2007;Wilken et al 2012;Yokoyama et al 2003).…”

Mating-Type Structure, Evolution, and Function in Euascomycetes

“…Evidence for MAT1-1-1 transcripts has been acquired by RT-PCR, but the transcriptional state of MAT1-1-2 is unknown. The MAT1-2 idiomorph contains the expected MAT1-2-1 gene but Yokoyama et al (2003) have identified an additional putative MAT1-1-1 pseudogene in this idiomorph. This pseudogene lacks the region encoding the α1 box, and the ORF has no initiation codon and is interrupted by several termination codons.…”

“…Transcripts for each of the MAT genes of F. oxysporum were found by RT-PCR, suggesting that the asexual feature of F. oxysporum does not result from a transcriptional deficiency. A total of 22 isolates of another asexual hypocreales, P. tenuipes (the sexual state of Cordyceps takaomontana), have been tested for their mating-type structure by Yokoyama et al (2003). Three contain the MAT1-1 idiomorph whereas 19 have the MAT1-2 idiomorph.…”

“…Reexamination of the sequence corresponding to the pseudogene of strain BCMUJ13 allowed us to identify a gene that includes two introns and a coding sequence of 339 residues, starting with a methionine initiation codon (MAT1-2-2, Table 15.1, Debuchy, unpublished data). Although Yokoyama et al (2003) have found MAT1-2-1 transcripts by RT-PCR, they have not searched for transcripts originating from the region corresponding to the putative MAT1-1-1 pseudogene. Further investigations will be required to establish whether this region corresponds to a pseudogene or to a new gene.…”