Changes in Trichoderma asperellum enzyme expression during parasitism of the cotton root rot pathogen...

The present study determined the activity of hydrolytic enzymes and the gene expression during direct interaction of the novelTrichoderma asperellumstrains TC74 (high antagonistic capacity) and Th1 (low antagonistic capacity) with the plant pathogenic fungusPhymatotrichopsis omnivora. TheT. asperellumstrains produced the lytic enzymes endochitinase, N-acetylglucosaminidase and β-1,3-glucanase when grown on two different carbon sources. The response of strain TC74 was more rapid than that of strain Th1. When directly exposed toP. omnivora, theT. asperellumstrains expressed one endochitinase and one N-acetylglucosaminidase, as shown by RT-PCR experiments. The strains also expressed two β-1,3-exoglucanases (designated as exg290 and exg343). TC74 and Th1 were able to express their chitinases and β-1,3-exoglucanase activities when grown on the different carbon sources tested. When theT. asperellumstrains were grown in the presence ofP. omnivora, qRT-PCR experiments revealed that mycoparasitism-related genes were first expressed prior to contact between the antagonist and the pathogen's mycelium. As a general response, the transcription level of these genes was increased at the post-contact stage. Although TC74 and Th1 both express the assayed genes when grown in direct contact withP. omnivora, significant differences in the time, intensity and kinetics of the response were observed.