Molecular docking of protease from Metarhizium anisopliae and their toxic effect against model insect Galleria mellonella

Fungal virulence has been mostly associated with cuticle-degrading enzymes, which form the first formidable barrier to pathogens and pass through certain discrete stages before breaching the insect cuticle. The present study was conducted to extract and purify the extracellular protease enzyme from three isolates from Metarhizium anisopliae. The molecular weight of protease enzyme from each isolate was identified using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and found to be 35-40kDa. The partially purified enzymes were tested to identify its toxic effects against the developmental stages of IV^th instar larvae of Galleria mellonella and the mortality of larvae among the three isolates was observed. The Tk6 isolate showed an ascending effect after 48h of exposure, with highest mortality at 120h post inoculation. It also showed more virulence against the model insect compared to other strains. Tk6 isolate's active protein band was analyzed by MALDI-TOF and docking study was carried out to find the interaction between the fungal and insect proteins.

Construction and preliminary analysis of a normalized cDNA library from Locusta migratoria manilensis topically infected with Metarhizium anisopliae var. acridum

The insect immune response to fungal infection is poorly understood at the molecular level. To explore the molecular basis of this process, a novel method to analyze the gene transcripts of insects in response to pathogenic fungus was established. A normalized cDNA library based on the SMART method combined with DSN (duplex-specific nuclease) treatment was constructed using mRNA extracted from the fat body and hemocytes of Locusta migratoria manilensis 6-24h after being topically infected with Metarhizium anisopliae var. acridum. Analysis of 259 unigenes out of 303 sequenced inserts from the cDNA library revealed that the cDNA library was not contaminated with M. anisopliae transcripts and validated the presence of the immune-related genes characterized here. These results suggest that this method overcame the difficulties of contamination from a fungal source in constructing the host cDNA library from mycosed insects and proved that this method is reliable and feasible for investigation of host genes in response to fungal infection. Further studies of the expressed sequence tags from this library will provide insights into the molecular basis of insect immune response to fungal infection.

A proteomic view into infection of greyback canegrubs (Dermolepida albohirtum) by Metarhizium anisopliae

Metarhizium anisopliae is a naturally occurring cosmopolitan fungus infecting greyback canegrubs (Dermolepida albohirtum). The main molecular factors involved in the complex interactions occurring between the greyback canegrubs and M. anisopliae (FI-1045) were investigated by comparing the proteomes of healthy canegrubs, canegrubs infected with Metarhizium and fungus only. Differentially expressed proteins from the infected canegrubs were subjected to mass spectrometry to search for pathogenicity related proteins. Immune-related proteins of canegrubs identified in this study include cytoskeletal proteins (actin), cell communication proteins, proteases and peptidases. Fungal proteins identified include metalloproteins, acyl-CoA, cyclin proteins and chorismate mutase. Comparative proteome analysis provided a view into the cellular reactions triggered in the canegrub in response to the fungal infection at the onset of biological control.

A 24 kDa parasitism-specific protein from the Caribbean fruit fly, Anastrepha suspensa: cDNA and deduced amino acid sequence

A 24 kDa parasitism-specific protein (PSP24) was previously reported from the hemolymph of the Caribbean fruit fly, Anastrepha suspensa (Diptera: Tephritidae) after parasitization by the wasp Diachasmimorpha longicaudata (Hymenoptera: Braconidae). This study was designed to sequence the open reading frame of PSP24 and to determine whether it is encoded by the wasp, fruit fly host or by the entomopoxvirus D1EPV which is normally injected into the host with the wasp's egg. Utilizing an existing partial amino acid sequence of PSP24, we obtained two cDNAs by reverse transcription-polymerase chain reaction, from the host hemolymph 48 h post parasitization. The smaller cDNA has an open reading frame (ORF) that encodes 85 amino acids (aa) with a molecular mass of 9711.33 Da and the larger encodes 203 aa with a molecular mass of 23,076 Da. Both cDNAs share a common N-terminus with a signal peptide predictive of secreted proteins, a characteristic that agrees with the observed nature of PSP24. The mature proteins have 39 and 157 aa with deduced molecular masses of 4286.86 Da and 17,651 Da, respectively. Western blots of host hemolymph probed with the anti-PSP24 serum reveal proteins of 0.10 and 0.24 kD, respectively. The discrepancy between the deduced and the observed molecular masses may be explained by their predicted O-linked glycosylation. The amino acid sequences are not homologous with any protein in the available databases. Southern blot hybridization experiments revealed that the proteins are encoded by both the host and the parasite. Furthermore, injection of D1EPV into healthy fruit fly puparia induces the two proteins. Thus, in surprising contrast to an earlier hypothesis that D1EPV encodes PSP24, these results clearly demonstrate that the PSP24 proteins are encoded by wasp and fruit fly but not D1EPV genes. However, their expression is D1EPV induced.