Identification of microRNA-like RNAs in Cordyceps guangdongensis and their expression profile under differential developmental stages.

Cordyceps guangdongensis is a well-known fungus with high nutritional and medicinal value. The metabolite profile of C. guangdongensis is similar to that of Ophiocordyceps sinensis. In plants and animals, microRNAs play important roles in regulating gene expression at the post-transcriptional level. MicroRNA-like RNAs (milRNAs) have been documented in several macro-fungi. To comprehensively investigate the milRNAs in C. guangdongensis, three small RNA libraries from the differentially developmental stages were constructed. Twenty-six conserved milRNAs were identified, and 19 novel milRNA candidates were predicted. Among them, 20 milRNAs were differentially expressed across the developmental processes, and 12 milRNAs were verified using stem-loop quantitative real-time reverse transcription polymerase chain reaction. In addition, the potential target genes of milRNA were predicted to be involved in the development of fruiting bodies and metabolite biosynthesis. This study is the first to report the milRNAs of C. guangdongensis, and provides important insights into studies of milRNA regulation pathways in ascomycete fungi.

Transcriptome and proteome analyses reveal the regulatory networks and metabolite biosynthesis pathways during the development of Tolypocladium guangdongense.

Tolypocladium guangdongense has a similar metabolite profile to Ophiocordyceps sinensis, a highly regarded fungus used for traditional Chinese medicine with high nutritional and medicinal value. Although the genome sequence of T. guangdongense has been reported, relatively little is known about the regulatory networks for fruiting body development and about the metabolite biosynthesis pathways. In order to address this, an analysis of transcriptome and proteome at differential developmental stages of T. guangdongense was performed. In total, 9076 genes were found to be expressed and 2040 proteins were identified. There were a large number of genes that were significantly differentially expressed between the mycelial stage and the stages. Interestingly, the correlation between the transcriptomic and proteomic data was low, suggesting the importance of the post-transcriptional processes in the growth and development of T. guangdongense. Among the genes/proteins that were both differentially expressed during the developmental process, there were numerous heat shock proteins and transcription factors. In addition, there were numerous proteins involved in terpenoid, ergosterol, adenosine and polysaccharide biosynthesis that also showed significant downregulation in their expression levels during the developmental process. Furthermore, both tryptophan and tryptamine were present at higher levels in the primordium stage. However, indole-3-acetic acid (IAA) levels continuously decreased as development proceeded, and the enzymes involved in IAA biosynthesis were also clearly differentially downregulated. These data could be meaningful in studying the molecular mechanisms of fungal development, and for the industrial and medicinal application of macro-fungi.

Selection and validation of reliable reference genes for Tolypocladium guangdongense gene expression analysis under differentially developmental stages and temperature stresses.

Tolypocladium guangdongense, formerly known as Cordyceps guangdongensis, is a widely cultivated fungus of the Cordyceps s.l. species that has been investigated over the last 12 years. It has the potential to be used in a number of applications in the health and pharmaceutical industries for it has shown its high nutritional and medicinal values according to previous animal studies. qRT-PCR (quantitative reverse transcription polymerase chain reaction) is extensively used to analyze the expression pattern and molecular mechanisms of functional genes under differentially experimental conditions. The expression stability of reference genes used for normalization determines the reliability of qRT-PCR results, indicating the importance of selection and validation of reference genes before gene expression analysis. In the present study, three statistical algorithms, geNorm, NormFinder and BestKeeper, were used for analyzing the expression stability of nineteen candidate reference genes (CRGs) in T. guangdongense. Investigation were carried out under differentially experimental conditions, which included differentially developmential stages (mycelia, primordia, young and mature fruiting bodies), different carbon sources, cold and heat stresses. The results showed that histone H4 and tubulin beta chain 2 (ß-tub2) were the most and least stable genes, respectively, across all the experimental samples. Moreover, analysis of individual data sets exhibited different stability and expression profiles of reference genes. The vacuolar protein sorting gene VPS was the most stable gene expressed under the differentially developmental stages and temperature stresses, whereas H4 was the most stably expressed gene under different carbon sources. Therefore, it can be proposed that VPS and H4 are the preferred reference genes for normalization of gene expression under different experimental conditions. The results of our present study will enable more accurate evaluation of gene expression in T. guangdongense using the optimal reference gene for qRT-PCR analysis.

Expression profiling of Cordyceps DnaJ protein family in Tolypocladium guangdongense during developmental and temperature stress processes.

DnaJ is an important molecular chaperone, with significant roles in growth, development, and stress resistance. Studies on the DnaJ gene family in macro-fungi such as Cordyceps spp. s.l. is scare. In this study, 22, 20, and 24 putative DnaJ genes were identified in Tolypocladium guangdongense, Ophiocordyceps sinensis, and C. militaris, respectively. They were classified into four groups based on the presence of the J, zinc finger, and C-terminal domains. We mainly studied the T. guangdongense DnaJ genes being located in the endoplasmic reticulum, cytoplasm, mitochondrion, and nucleus. Phylogenetic analysis revealed gene duplications during the evolutionary process. Multiple cis-elements and transcription factor binding sites were observed in the promoter, suggesting their involvement in the response to multiple stresses. qRT-PCR analysis showed that 63.63% and 45.45% of T. guangdongense DnaJ genes were differentially expressed under cold and heat stress, respectively, indicating their involvement in the response to temperature stress. Many T. guangdongense DnaJ genes in the primordium and fruiting body exhibited differential expression, in comparison to those in the mycelium, suggesting a regulatory role in its growth and development process. These findings will facilitate further functional analysis, and provide information on the classification and conservative functions of DnaJ proteins in macro-fungi.