Open Access
Highly expressed captured genes and cross-kingdom domains present in Helitrons create novel diversity in Pleurotus ostreatus and other fungi
(BioMed Central, 2014) Castanera Andrés, Raúl; Pérez Garrido, María Gumersinda; López Varas, Leticia; Sancho, Rubén; Santoyo Santos, Francisco; Alfaro Sánchez, Manuel; Gabaldón Estevan, Juan Antonio; Pisabarro de Lucas, Gerardo; Oguiza Tomé, José Antonio; Ramírez Nasto, Lucía; Producción Agraria; Nekazaritza Ekoizpena; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Background: Helitrons are class-II eukaryotic transposons that transpose via a rolling circle mechanism. Due to their ability to capture and mobilize gene fragments, they play an important role in the evolution of their host genomes. We have used a bioinformatics approach for the identification of helitrons in two Pleurotus ostreatus genomes using de novo detection and homology-based searching. We have analyzed the presence of helitron-captured genes as well as the expansion of helitron-specific helicases in fungi and performed a phylogenetic analysis of their conserved domains with other representative eukaryotic species. Results: Our results show the presence of two helitron families in P. ostreatus that disrupt gene colinearity and cause a lack of synteny between their genomes. Both putative autonomous and non-autonomous helitrons were transcriptionally active, and some of them carried highly expressed captured genes of unknown origin and function. In addition, both families contained eukaryotic, bacterial and viral domains within the helitron’s boundaries. A phylogenetic reconstruction of RepHel helicases using the Helitron-like and PIF1-like helicase conserved domains revealed a polyphyletic origin for eukaryotic helitrons. Conclusion: P. ostreatus helitrons display features similar to other eukaryotic helitrons and do not tend to capture host genes or gene fragments. The occurrence of genes probably captured from other hosts inside the helitrons boundaries pose the hypothesis that an ancient horizontal transfer mechanism could have taken place. The viral domains found in some of these genes and the polyphyletic origin of RepHel helicases in the eukaryotic kingdom suggests that virus could have played a role in a putative lateral transfer of helitrons within the eukaryotic kingdom. The high similarity of some helitrons, along with the transcriptional activity of its RepHel helicases indicates that these elements are still active in the genome of P. ostreatus.
Open Access
Comparative and transcriptional analysis of the predicted secretome in the lignocellulose-degrading basidiomycete fungus Pleurotus ostreatus
(Wiley, 2016) Alfaro Sánchez, Manuel; Castanera Andrés, Raúl; Lavín Trueba, José Luis; Oguiza Tomé, José Antonio; Ramírez Nasto, Lucía; Pisabarro de Lucas, Gerardo; Producción Agraria; Nekazaritza Ekoizpena; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Fungi interact with their environment by secreting proteins to obtain nutrients, elicit responses and modify their surroundings. Because the set of proteins secreted by a fungus is related to its lifestyle, it should be possible to use it as a tool to predict fungal lifestyle. To test this hypothesis, we bioinformatically identified 538 and 554 secretable proteins in the monokaryotic strains PC9 and PC15 of the white rot basidiomycete Pleurotus ostreatus. Functional annotation revealed unknown functions (37.2%), glycosyl hydrolases (26.5%) and redox enzymes (11.5%) as the main groups in the two strains. When these results were combined with RNA‐seq analyses, we found that the relative importance of each group was different in different strains and culture conditions and the relevance of the unknown function proteins was enhanced. Only a few genes were actively expressed in a given culture condition in expanded multigene families, suggesting that family expansi on could increase adaptive opportunities rather than activity under a specific culture condition. Finally, we used the set of P. ostreatus secreted proteins as a query to search their counterparts in other fungal genomes and found that the secretome profiles cluster the tested basidiomycetes into lifestyle rather than phylogenetic groups.
Open Access
Transcriptional and enzymatic profiling of Pleurotus ostreatus laccase genes in submerged and solid-state fermentation cultures
(American Society for Microbiology, 2012) Castanera Andrés, Raúl; Pérez Garrido, María Gumersinda; Omarini, Alejandra; Alfaro Sánchez, Manuel; Pisabarro de Lucas, Gerardo; Faraco, Vicenza; Amore, Antonella; Ramírez Nasto, Lucía; Producción Agraria; Nekazaritza Ekoizpena; Gobierno de Navarra / Nafarroako Gobernua; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
The genome of the white rot basidiomycete Pleurotus ostreatus includes 12 phenol oxidase (laccase) genes. In this study, we examined their expression profiles in different fungal strains under different culture conditions (submerged and solid cultures) and in the presence of a wheat straw extract, which was used as an inducer of the laccase gene family. We used a reverse transcription- quantitative PCR (RT-qPCR)-based approach and focused on determining the reaction parameters (in particular, the reference gene set for the normalization and reaction efficiency determinations) used to achieve an accurate estimation of the relative gene expression values. The results suggested that (i) laccase gene transcription is upregulated in the induced submerged fermentation (iSmF) cultures but downregulated in the solid fermentation (SSF) cultures, (ii) the Lacc2 and Lacc10 genes are the main sources of laccase activity in the iSmF cultures upon induction with water-soluble wheat straw extracts, and (iii) an additional, as-yet-uncharacterized activity (Unk1) is specifically induced in SSF cultures that complements the activity of Lacc2 and Lacc10. Moreover, both the enzymatic laccase activities and the Lacc gene family transcription profiles greatly differ between closely related strains. These differences can be targeted for biotechnological breeding programs for enzyme production in submerged fermentation reactors.
Open Access
Genomics and transcriptomics characterization of genes expressed during postharvest at 4 degrees C by the edible basidiomycete Pleurotus ostreatus
(Viguera Editores, S. L., 2011) Ramírez Nasto, Lucía; Oguiza Tomé, José Antonio; Pérez Garrido, María Gumersinda; Lavín Trueba, José Luis; Omarini, Alejandra; Santoyo Santos, Francisco; Alfaro Sánchez, Manuel; Castanera Andrés, Raúl; Parenti, Alejandra; Muguerza Domínguez, Elaia; Pisabarro de Lucas, Gerardo; Producción Agraria; Nekazaritza Ekoizpena
Pleurotus ostreatus is an industrially cultivated basidiomycete with nutritional and environmental applications. Its genome, which was sequenced by the joint Genome Institute, has become a model for lignin degradation and for fungal genomics and transcriptomics studies. The complete P. ostreatus genome contains 35 Mbp organized in 11 chromosomes, and two different haploid genomes have been individually sequenced. In this work, genomics and transcriptomics approaches were employed in the study of P. ostreatus under different physiological conditions. Specifically, we analyzed a collection of expressed sequence tags (EST) obtained from cut fruit bodies that had been stored at 4 degrees C for 7 days (postharvest conditions). Studies of the 253 expressed clones that had been automatically and manually annotated provided a detailed picture of the life characteristics of the self-sustained fruit bodies. The results suggested a complex metabolism in which autophagy, RNA metabolism, and protein and carbohydrate turnover are increased. Genes involved in environment sensing and morphogenesis were expressed under these conditions. The data improve our understanding of the decay process in postharvest mushrooms and highlight the use of high-throughput techniques to construct models of living organisms subjected to different environmental conditions.
Open Access
Genomic, transcriptomic and proteomic analysis of Pleurotus ostreatus secreted proteins
(2017) Alfaro Sánchez, Manuel; Pisabarro de Lucas, Gerardo; Producción Agraria; Nekazaritza Ekoizpena
The objective of this thesis is to study the proteins secreted by the edible and worldwide cultivated white rot basidiomycete fungus Pleurotus ostreatus with three major goals: to determine the set of proteins secreted under different nutritional conditions, to determine the effect of the monokaryotic and dikaryotic mycelial conditions on the secretome, and to explore the relationship between the transcriptome of the secreted proteins and the actual secretome in different monokaryotic strains. In the first chapter of this thesis, we will review several basidiomycete secretome analyses comparing the results obtained using different analytical techniques and discussing some representative examples. We will pay a special attention to the lignocellulolytic enzymes secreted and to the different fungal lifestyles. This chapter is an updated version of the paper entitled Comparative analysis of secretomes in basidiomycete fungi that we published in Journal of Proteomics in 2014 as a summary of the state of the art. The main conclusions of this chapter are that a combination of genomic, transcriptomic and proteomics techniques is still the best approach for analyzing fungal secretomes, allowing to the identification of secretion patterns associated to the different lifestyles. In the third chapter, we screened two P. ostreatus monokaryotic genomes to identify bioinformatically the genes coding for proteins targeted for secretion. The study was made using the two monokaryotic protoclones (mkPC9 and mkPC15) whose genomes had been previously sequenced and annotated in a collaborative project carried out with the Joint Genome Institute. These two protoclones contain the two nuclei present in the commercial dikaryotic strains dkN001. The results obtained showed that, surprisingly, both strains differ in their lignocellulose degrading genomic capabilities. mkPC9 have less CAZy genes annotated, especially in the Glycosil hydrolases (GH) class. Nevertheless, mkPC9 grows better than mkPC15 on lignocellulosic substrates and has a higher enzyme secretion capacity when growing in the presence of wood. The transcription of the genes coding for secretable proteins was studied by RNAseq analysis and we could conclude that, whereas the genome profile of the secretome was similar in the two strains, the corresponding transcriptome profiles were different between them and in different culture conditions and we observed a concentrated transcriptional activity in few genes per function and an increased importance of the glycosil hydrolases and proteins without a functional classification. These results highlight the importance of adding additional data to the gene lists produced by genome sequence analysis for gaining a more accurate picture of the biological process under study. P. ostreatus secretes a huge variety of lignocellulose degrading enzymes when cultured in the presence of wood. More than 20% of them lack a known enzymatic function. Transcriptome analysis noted the importance of these proteins, further confirmed by proteomics. Using domain structure prediction, we were able to give an insight about the possible role of several proteins, including a xylanase and a AA10 LPMO. This chapter is a version of the manuscript entitled Comparative and transcriptional analysis of the predicted secretome in the lignocellulose‐degrading basidiomycete fungus Pleurotus ostreatus published in Environmental Microbiology. Finally, in the fourth chapter, mass spectrometry analyses were used to confirm the presence of these enzymes acting on the lignocellulosic substrates. We compared the proteins secreted by the two monokaryons studied in the bioinformatics analysis with that of dikaryon that contains the two nuclei present in them. Interestingly, monokaryons behave in a very different manner; mkPC15 showed a weakest production of lignocellulose degrading enzymes than mkPC9 and dkN001 when cultured using wood as a carbon source. Moreover, dkN001 was able to secrete more plant cell wall decomposing enzymes, correlating with their superior capacity to grow on lignocellulosic substrates. Furthermore, the three strains were cultured in three different media using with glucose, wood or both (glucose and wood) as a carbon source. As expected, we identify a higher number of lignocellulose degrading enzymes in wood-containing media, especially glycosyl-hydrolases, carbohydrate esterases and polysaccharide lyases. Fungal lignocellulose degradation is the result of the synergistic action of several enzymes. These thesis improve our overall understanding of plant biomass degradation as a step to achieve the goal of using biomass as a sustainable source of energy to support future needs.