Abstract
BackgroundEukaryotic organisms employ cell surface receptors such as the seven-transmembrane G protein-coupled receptors (GPCRs) as sensors to connect to the environment. GPCRs react to a variety of extracellular cues and are considered to play central roles in the signal transduction in fungi. Several species of the filamentous ascomycete Trichoderma are potent mycoparasites, i.e. can attack and parasitize other fungi, which turns them into successful bio-fungicides for the protection of plants against fungal phytopathogens. The identification and characterization of GPCRs will provide insights into how Trichoderma communicates with its environment and senses the presence of host fungi.ResultsWe mined the recently published genomes of the two mycoparasitic biocontrol agents Trichoderma atroviride and Trichoderma virens and compared the identified GPCR-like proteins to those of the saprophyte Trichoderma reesei. Phylogenetic analyses resulted in 14 classes and revealed differences not only among the three Trichoderma species but also between Trichoderma and other fungi. The class comprising proteins of the PAQR family was significantly expanded both in Trichoderma compared to other fungi as well as in the two mycoparasites compared to T. reesei. Expression analysis of the PAQR-encoding genes of the three Trichoderma species revealed that all except one were actually transcribed. Furthermore, the class of receptors with a DUF300 domain was expanded in T. atroviride, and T. virens showed an expansion of PTH11-like receptors compared to T. atroviride and T. reesei.ConclusionsComparative genome analyses of three Trichoderma species revealed a great diversity of putative GPCRs with genus- and species- specific differences. The expansion of certain classes in the mycoparasites T. atroviride and T. virens is likely to reflect the capability of these fungi to establish various ecological niches and interactions with other organisms such as fungi and plants. These GPCRs consequently represent interesting candidates for future research on the mechanisms underlying mycoparasitism and biocontrol.
Highlights
Eukaryotic organisms employ cell surface receptors such as the seven-transmembrane G protein-coupled receptors (GPCRs) as sensors to connect to the environment
Identification of G protein-coupled receptor-like proteins in the genomes of three Trichoderma species The T. atroviride, T. virens and T. reesei genome databases were searched for putative GPCRs using a homology (BLAST)-based strategy
Together with the putative GPCRs identified in the genome of Neurospora crassa [2] and Phytophtora sojae GPR11 [35], the 18 GPCRs previously identified in Aspergillus spp. [1] and the three new GPCRs predicted in the Verticillium genome [36] were used in a BLASTP search against the predicted proteomes of the following species of the Sordariomycetes (Magnaporthe grisea, Podospora anserina, Chaetomium globosum, Fusarium graminearum, Nectria haematococca, T. reesei, T. atroviride and T. virens), a subgroup within the Ascomycota
Summary
Eukaryotic organisms employ cell surface receptors such as the seven-transmembrane G protein-coupled receptors (GPCRs) as sensors to connect to the environment. The relatively simple structure and the ease of cultivation and genetic manipulation make fungi interesting eukaryotic models for studying fundamental biological processes. They share important features with even mammalian cells. In recent years several intracellular partners other than G proteins were identified that are capable of mediating signals originating from these receptors These include arrestins, G protein-coupled receptor kinases, small GTP-binding proteins, and many more [10,11,12,13]. Pheromone- and nutrient- sensing GPCRs have been studied extensively in yeast and some filamentous fungi [14,15,16,17,18,19,20,21,22,23,24,25,26] far more GPCRs remain to be identified and characterized
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