title: Sexual reproduction as the cause of heat resistance in the food spoilage fungus Byssochlamys spectabilis (anamorph Paecilomyces variotii).
abstract: Paecilomyces variotii is a common cosmopolitan species that is able to spoil various food- and feedstuffs and is frequently encountered in heat-treated products. However, isolates from heat-treated products rarely form ascospores. In this study we examined by using molecular techniques and mating tests whether this species can undergo a sexual cycle and form ascospores. The population structure of this species was examined by analyzing the nuclear ribosomal internal transcribed spacer 1 (ITS1) and ITS2 and the 5.8S rRNA gene, as well as partial beta-tubulin, actin, and calmodulin gene sequences. Phylogenetic analyses revealed that P. variotii is a highly variable species. Partition homogeneity tests revealed that P. variotii has a recombining population structure. In addition to sequence analyses, mating experiments indicated that P. variotii is able to form ascomata and ascospores in culture in a heterothallic manner. The distribution of MAT1-1 and MAT1-2 genes showed a 1:1 ratio in the progeny of the mating experiments. From the sequence analyses and mating data we conclude that P. variotii is the anamorph of Talaromyces spectabilis and that it has a biallelic heterothallic mating system. Since Paecilomyces sensu stricto anamorphs group within Byssochlamys, a new combination Byssochlamys spectabilis is proposed.
authors.affiliation: Department of Applied and Industrial Mycology, CBS Fungal Biodiversity Centre, Uppsalalaan 8, PO Box 85167, 3508 AD Utrecht, The Netherlands.
authors.forename: Jos
authors.initials: J
authors.lastname: Houbraken
authors.forename: János
authors.initials: J
authors.lastname: Varga
authors.forename: Emilia
authors.initials: E
authors.lastname: Rico-Munoz
authors.forename: Shawn
authors.initials: S
authors.lastname: Johnson
authors.forename: Robert A
authors.initials: RA
authors.lastname: Samson
mesh_terms: D000199:Actins / Q000235:genetics; D000222:Adaptation, Physiological / Q000502:physiology*; D001483:Base Sequence; D002147:Calmodulin / Q000235:genetics; D016000:Cluster Analysis; D003433:Crosses, Genetic; D017931:DNA Primers; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D005516:Food Microbiology; D005828:Genetics, Population; D006358:Hot Temperature; D008969:Molecular Sequence Data; D010143:Paecilomyces / Q000145:classification / Q000235:genetics* / Q000502:physiology*; D010802:Phylogeny; D012340:RNA, Ribosomal, 5.8S / Q000235:genetics; D012098:Reproduction / Q000502:physiology; D017422:Sequence Analysis, DNA; D013172:Spores, Fungal / Q000502:physiology*; D014404:Tubulin / Q000235:genetics
chemical_list: D000199:Actins; D002147:Calmodulin; D017931:DNA Primers; D021903:DNA, Ribosomal Spacer; D012340:RNA, Ribosomal, 5.8S; D014404:Tubulin