Biological control of agricultural pests by filamentous fungi

Integrative Analyses of Transcriptomics and Metabolomics in Immune Response of Leguminivora glycinivorella Mats to Beauveria bassiana Infection

This study utilized Beauveria bassiana to infect Leguminivora glycinivorella, analyzed the effects on the transcriptome and metabolome, and further investigated the antibacterial function of L. glycinivorella. We performed transcriptome and metabolome sequencing on the L. glycinivorella infected with B. bassiana and its control groups, and performed a joint analysis of transcriptome and metabolome results. Upon screening, 4560 differentially expressed genes were obtained in the transcriptome and 71 differentially expressed metabolites were obtained in the metabolome. On this basis, further integration of the use of transcriptomics and metabonomics combined an analysis of common enrichments of pathways of which there were three. They were glutathione S-transferase (GSTs) genes, heat shock protein (HSP) genes, and cytochrome P450 (CYP450) genes. These three pathways regulate the transport proteins, such as ppars, and thus affect the digestion and absorption of sugars and fats, thus regulating the development of pests. The above conclusion indicates that B. bassiana can affect the sugar metabolism, lipid metabolism, and amino acid metabolism pathways of L. glycinivorella, and can consume the necessary energy, protein, and lipids of L. glycinivorella. The research on the immune response mechanism of pests against pathogens can provide an important scientific basis and target for the development of immunosuppressants. This study laid an information foundation for the application of entomogenous fungi to control soybean borer at the molecular level.

In vitro water activity and pH dependence of mycelial growth and extracellular enzyme activities of Trichoderma strains with biocontrol potential

AIMS

Water activity (aw) and pH are probably the most important environmental parameters affecting the activities of mycoparasitic Trichoderma strains. Therefore it is important to collect information on the effects of these factors on mycelial growth and on the in vitro activities of extracellular enzymes involved in nutrient competition (e.g. beta-glucosidase, cellobiohydrolase and beta-xylosidase) and mycoparasitism (e.g. N-acetyl-beta-glucosaminidase, trypsin-like protease and chymotrypsin-like protease) of Trichoderma strains with biocontrol potential.

METHODS AND RESULTS

Water activity and pH dependence of the linear mycelial growth of five examined Trichoderma strains belonging to three different species groups was examined on yeast extract and soil extract media. Maximal growth rates were observed at aw 0.997 and pH 4.0 in the case of all strains. The activities of the examined extracellular enzymes at different aw and pH values were determined spectrophotometrically after incubation with chromogenic p-nitrophenyl and p-nitroaniline substrates. Maximal enzyme activities were measured at aw 0.950 for beta-glucosidase, trypsin-like protease and chymotrypsin-like protease, at 0.910 for cellobiohydrolase and at 0.993 for beta-xylosidase and N-acetyl-beta-glucosaminidase enzymes. Optimal pH values are suggested to be at 5.0 for beta-glucosidase, cellobiohydrolase and N-acetyl-beta-glucosaminidase, at 3.0 for beta-xylosidase, at 6.0 for trypsin-like protease and between 6.0 and 7.0 for chymotrypsin-like protease activities, respectively.

CONCLUSIONS

Extracellular enzymes of the examined mycoparasitic Trichoderma strains are able to display activities under a wider range of aw and pH values than those allowing mycelial growth.

SIGNIFICANCE AND IMPACT OF THE STUDY

Data about the effects of aw and pH on mycelial growth and extracellular enzyme activities of Trichoderma reveal useful information about the applicability of biocontrol strains in agricultural soils with specific water and pH relations.