Transcriptomic response of the mycoparasitic fungus Trichoderma atroviride to the presence of a fungal prey

Abstract

BackgroundCombating the action of plant pathogenic microorganisms by mycoparasitic fungi has been announced as an attractive biological alternative to the use of chemical fungicides since two decades. The fungal genus Trichoderma includes a high number of taxa which are able to recognize, combat and finally besiege and kill their prey. Only fragments of the biochemical processes related to this ability have been uncovered so far, however.ResultsWe analyzed genome-wide gene expression changes during the begin of physical contact between Trichoderma atroviride and two plant pathogens Botrytis cinerea and Rhizoctonia solani, and compared with gene expression patterns of mycelial and conidiating cultures, respectively. About 3000 ESTs, representing about 900 genes, were obtained from each of these three growth conditions. 66 genes, represented by 442 ESTs, were specifically and significantly overexpressed during onset of mycoparasitism, and the expression of a subset thereof was verified by expression analysis. The upregulated genes comprised 18 KOG groups, but were most abundant from the groups representing posttranslational processing, and amino acid metabolism, and included components of the stress response, reaction to nitrogen shortage, signal transduction and lipid catabolism. Metabolic network analysis confirmed the upregulation of the genes for amino acid biosynthesis and of those involved in the catabolism of lipids and aminosugars.ConclusionThe analysis of the genes overexpressed during the onset of mycoparasitism in T. atroviride has revealed that the fungus reacts to this condition with several previously undetected physiological reactions. These data enable a new and more comprehensive interpretation of the physiology of mycoparasitism, and will aid in the selection of traits for improvement of biocontrol strains by recombinant techniques.

Trichoderma Research in the Genome Era

“…An EST-based analysis of gene expression patterns at the beginning of physical contact between T. atroviride and B. cinerea/R. solani identified 66 genes that were overexpressed during the onset of mycoparasitism (123). The most abundant genes were involved in posttranslational processing and amino acid metabolism.…”

Pythium oligandrum: an example of opportunistic success

“…Once effective binding is achieved, a cascade involving mitogen-activated protein kinases (MAPKs) (Mukherjee et al, 2003) regulates the activity of transcription factors (currently unidentified) that, in turn, trigger the activation of constitutive genes encoding proteins and enzymes such as cell-wall-degrading enzymes (Druzhinina et al, 2011). Support for this hypothesis comes from the finding that several genes encoding subtilisin-like serine proteases and oligopeptide transporters are overexpressed before and during contact with the prey in at least three Trichoderma species that have been sequenced (Seidl et al, 2009). Evidence is also provided that the overexpression of proteases confers an enhanced mycoparasitic activity to these Trichoderma strains (Flores et al, 1997).…”

Reproduction without sex: conidiation in the filamentous fungus Trichoderma

“…Expression of this gene is considered specific to conidiophores and conidia, and has been extended to other Trichoderma strains (our unpublished results). Multiple potential markers for conidiation have been identified in T. atroviride and include Spo14 (encodes phospholipase D), Spo75 (meiosis-specific protein, required for spore formation), StuI (encodes a cell pattern formation-associated protein) and Wet1 (developmental regulatory protein), and the hydrophobin genes srh1 (hfb2), hfb-2c, hfb-6a and hfb-6b (Mikus et al, 2009;Muñoz et al, 1997;Seidl et al, 2009). …”