Two Strains of Lentinula edodes Differ in Their Transcriptional and Metabolic Patterns and Respond Differently to Thermostress

Temperature type is one of the key traits determining the cultivation regime of Lentinula edodes. However, the molecular and metabolic basis underling temperature type remain unclear. Here, we investigated the phenotypic, transcriptomic, and metabolic features of L. edodes with different temperature types under both control (25 °C) and high (37 °C) temperature conditions. We found that under the control condition, the high- and low-temperature types of L. edodes harbored distinct transcriptional and metabolic profiles. The high-temperature (H-)-type strain had a higher expression level of genes involved in the toxin processes and carbohydrate binding, while the low-temperature (L-)-type strain had a high expression level of oxidoreductase activity. Heat stress significantly inhibited the growth of both H- and L-type strains, while the latter had a higher growth inhibition rate. Upon exposure to heat, the H-type strain significantly up-regulated genes associated with the components of the cellular membrane, whereas the L-type strain markedly up-regulated genes involved in the extracellular region and carbohydrate binding. Metabolome data showed that thermostress altered purine and pyrimidine metabolism in the H-type strain, whereas it altered cysteine, methionine, and glycerophospholipid metabolism in the L-type strain. Transcriptome and metabolome integrative analysis was able to identify three independent thermotolerance-related gene-metabolite regulatory networks. Our results deepen the current understanding of the molecular and metabolic basis underlying temperature type and suggest, for the first time, that thermotolerance mechanisms can be temperature-type-dependent for L. edodes.

Cloning and characterization of two hydrophobin genes differentially expressed during fruit body development in Lentinula edodes

Hydrophobins play important roles in morphogenesis and pathogenesis in fungi and fruit development in mushrooms. Two genes encoding hydrophobins (Le.hyd1 and Le.hyd2) were isolated during sequencing of random clones from a primordial cDNA library of Lentinula edodes. The nucleotide sequences of these two genes were determined. These two genes are 760 and 738 bp in length and the deduced amino acid sequences are homologous to various fungal hydrophobins with characteristic cysteine spacing. These hydrophobin genes are Class I hydrophobins judging by their conserved domains and hydropathy patterns. The transcript level of Le.hyd1 is high in primordium and that of Le.hyd2 is high in dikaryotic mycelial tissues. Poor expression of these two genes in monokaryotic parents indicates that these two genes are under mating-type regulation. We thus suggest that differential expression of these two L. edodes hydrophobins during fruit development may contribute to their distinct roles in fruiting of this mushroom.

Evidence for two independent lineages of shiitake of the americas (Lentinula boryana) based on rDNA and beta-tubulin gene sequences

Portions of ribosomal RNA genes (rDNA) were sequenced from members of the genus Lentinula and were used, along with partial beta-tubulin gene sequences, for phylogenetic reconstructions. The rDNA sequences of L. boryana were separated into two well-defined lineages. Lineage 1 was composed of isolates from Mexico and Costa Rica while lineage 2 encompassed isolates from the United States, Venezuela, and Brazil. The two South American isolates of L. boryana had nearly identical ITS sequences and very closely related beta-tubulin sequences. This high level of similarity may indicate that sexual reproduction occurs among the sampled populations, although this is difficult to reconcile with the large geographic distances (over 4000 km) that separate some of the collecting locations. An alternative explanation may be that the isolates sampled are the product of a rapid population expansion over a large geographic area. Analyses of partial beta-tubulin gene sequences that were rooted using Pleurotus spp. support the hypothesis that L. boryana is monophyletic.