Nucleotide sequence of the 5.8S ribosomal RNA gene of Lentinula edodes

Global phylogeny of the Shiitake mushroom and related Lentinula species uncovers novel diversity and suggests an origin in the Neotropics

Lentinula (Basidiomycota, Agaricales) includes the most widely cultivated mushroom in the world, Lentinula edodes, also known as shiitake (Japanese) or xiang-gu (Chinese). At present, nine species are recognized in the genus, based on morphology, mating criteria, and geographic distributions. However, analyses of internal transcribed spacers (ITS) of ribosomal RNA genes have suggested that there are cryptic lineages. We analyzed a global-scale phylogenetic dataset from 325 Lentinula individuals from 24 countries in Asia-Australasia and the Americas plus Madagascar, with 325 sequences of ITS, 80 LSU sequences, and 111 sequences of translation elongation factor (tef1-α) genes. We recovered 15 independent lineages (Groups 1-15) that may correspond to species. Lineages in Asia-Australasia (Groups 1-5) and the Americas plus Madagascar (Groups 6-15) formed sister clades. Four lineages are represented only by sequences from single individuals and require further molecular sampling, including L. aff. raphanica (Group 7), L. ixodes (Group 8), L. boryana (Group 12), and L. aff. aciculospora (Group 14). Groups 1 and 5 are here referred to L. edodes and L. aff. edodes, respectively. However, these groups most likely represent the same species and are only recognized as (unsupported) monophyletic lineages by maximum likelihood analyses of ITS alone. Other putative species resolved here include L. lateritia (Group 2), L. novae-zelandieae (Group 3), L. aff. lateritia (Group 4), L. raphanica (Group 6), L. aff. detonsa (Group 9), L. detonsa (Group 10), L. guzmanii sp. nov. (Group 11), L. aciculospora (Group 13), and L. madagasikarensis (Group 15). Groups 9-12 represent the "L. boryana complex". Molecular clock and historical biogeographic analyses suggest that the most recent common ancestor (MRCA) of Lentinula can be placed in the middle Oligocene, ca. 30 million years ago (Ma), and had a likely presence in neotropical America. The MRCA of Lentinula in the Americas and Madagascar lived ca. 22 Ma in the Neotropics and the MRCA of Lentinula in Asia-Australasia lived ca. 6 Ma in Oceania. Given the current knowledge about plate tectonics and paleoclimatic models of the last 30 Myr, our phylogenetic hypothesis suggests that the extant distribution of Lentinula is likely to have arisen, in large part, due to long-distance dispersal. Lentinula collections include at least four dubious taxa that need further taxonomic studies: L. reticeps from the USA (Ohio); L. guarapiensis from Paraguay; Lentinus puiggarii from Brazil (São Paulo); and "L. platinedodes" from Vietnam. Approximately ten of the fifteen Groups are reported on Fagaceae, which appears to be the ancestral substrate of Lentinula.

Molecular characterizations of somatic hybrids developed between Pleurotus florida and Lentinus squarrosulus through inter-simple sequence repeat markers and sequencing of ribosomal RNA-ITS gene

The 12 pfls somatic hybrids and 2 parents of Pleurotus florida and Lentinus squarrosulus were characterized by ISSR and sequencing of rRNA-ITS genes. Five ISSR primers were used and amplified a total of 54 reproducible fragments with 98.14% polymorphism among all the pfls hybrid populations and parental strains. UPGMA-based cluster exhibited a dendrogram with three major groups between the parents and pfls hybrids. Parent P. florida and L. squarrosulus showed different degrees of genetic distance with all the hybrid lines and they showed closeness to hybrid pfls 1m and pfls 1h, respectively. ITS1(F) and ITS4(R) amplified the rRNA-ITS gene with 611-867 bp sequence length. The nucleotide polymorphisms were found in the ITS1, ITS2 and 5.8S rRNA region with different number of bases. Based on rRNA-ITS sequence, UPGMA cluster exhibited three distinct groups between L. squarrosulus and pfls 1p, pfls 1m and pfls 1s, and pfls 1e and P. florida.

Collection, characterization, and utilization of germ plasm of Lentinula edodes

Wild and cultivated strains of Lentinula edodes have been collected to form a germ-plasm bank of the mushroom. In addition to the ecological, morphological, and physical properties, the strains were characterized to determine their mating types (alleles of A and B incompatibility factors), substrate degradation abilities, mycelial growth rates, and fruiting abilities. The strains were used to establish molecular genetic methods of strain authentification. The genomic fingerprinting method of arbitrarily primed polymerase chain reaction was found to be a better method than the rDNA internal transcribed spacer regions sequence comparison for L. edodes strain typing. The utilization of the characterized germ-plasm bank for the selection of desirable germ plasm for breeding and cultivation is described. The value and use of molecular markers and genetic maps is also discussed. Key words: mating types, mycelial growth rate, molecular markers.

Nucleotide sequence analysis of the 5.8S rDNA and adjacent ITS2 region of Candida albicans and related species

We have determined the nucleotide sequence for the DNA encoding the 5.8S RNAs and downstream internal transcribed spacer (ITS2) regions for Candida albicans and the taxonomically related species C. parapsilosis, C. tropicalis, C. glabrata and C. krusei. Phylogenetic analysis of all known fungal 5.8S RNA sequences revealed a close relationship between C. tropicalis and C. parapsilosis, and to a lesser extent C. albicans within the yeast-like fungi. This group can itself be delineated from predominantly filamentous species. The more distal relationships between Candida (Torulopsis) glabrata and C. krusei support previous findings based on small (18S) ribosomal RNA sequence analysis, suggesting a greater degree of evolutionary divergence of these species from the C. albicans group. Among strains of C. albicans we observed conservation of the ITS2 region at the nucleotide level. Conservation was also observed for a more limited number of C. parapsilosis strains. Although the 3' region of the ITS spacer was species specific, sequence homology was observed in the 5' end within the albicans/parapsilosis/tropicalis group. Our findings suggest a rapid approach to species identification through the use of non-conserved regions flanked by highly conserved, functional domains.