Deletion of the Nonribosomal Peptide Synthetase Gene <i>nps1</i> in the Fungus <i>Clonostachys rosea</i> Attenuates Antagonism and Biocontrol of Plant Pathogenic <i>Fusarium</i> and Nematodes

Abstract

Secondary metabolites produced by biological control agents may influence the outcome of their interactions with plant pathogenic microorganisms and plants. In the present study, we investigated the role of the nonribosomal peptide synthetase gene <i>nps1</i> expressed by the biocontrol fungus <i>Clonostachys rosea</i>. A gene expression analysis showed that <i>nps1</i> was induced during confrontations with the plant pathogenic fungus <i>Botrytis cinerea</i>. Gene deletion strains of <i>nps1</i> displayed increased growth rates and conidiation. However, the nematicidal activity of culture filtrates from <i>C. rosea</i> Δ<i>nps1</i> strains was significantly weaker than that from wild-type filtrates (<i>P</i> ≤ 0.001); after 24 h of incubation with culture filtrates from <i>nps1</i> deletion strains, only 13 to 33% of a mixed community of nematodes were dead compared with 42% of nematodes incubated with wild-type culture filtrates. The Δ<i>nps1</i> strains also showed reduced biocontrol efficacy during pot experiments, thus failing to protect wheat seedlings from foot rot disease caused by the plant pathogenic fungus <i>Fusarium graminearum</i>. Furthermore, <i>C. rosea</i> Δ<i>nps1</i> strains were not able to reduce populations of plant-parasitic nematodes in soil or in roots of wheat as efficiently as the wild-type strain. Both <i>C. rosea</i> wild-type and Δ<i>nps1</i> strains increased the dry shoot weight and shoot length of wheat by 20 and 13%, respectively. We showed that NPS1, a putative nonribosomal peptide synthetase encoded by <i>nps1</i>, is a biocontrol factor, presumably by producing a hitherto unknown nonribosomal peptide compound with antifungal and nematicidal properties that contributes to the biocontrol properties of <i>C. rosea</i>.