Labeling membrane receptors with lectins and evaluation of the midgut histochemistry of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) populations with different levels of susceptibility to formulated Bt.

BACKGROUND: Studies show that insects can adapt to the toxins of Bacillus thuringiensis under field and laboratory conditions through the development of resistance to the bacterium and its formulations. This has been demonstrated in the failure to control Tuta absoluta populations in Brazil. This study evaluated membrane receptors using peroxidase-labeled lectins and the midgut histochemistry of T. absoluta populations to assess susceptibility to the insecticides Bt fomulations. The histochemistry analysis used Periodic Acid-Schiff for glycogen and Ponceau Xylidine for total proteins. The presence of glucose/mannose and N-acetylgalactosamine (GalNAc) was analyzed using specific lectins. One susceptible and one tolerant population were used in the study; insects were exposed to the insecticide concentrations recommended by the manufacturers. The midgut was collected after an interval of 20 min and analyzed using optical microscopy. RESULTS: Bt fomulation interferes with the glycogen content, whereas XenTari® interferes with the protein content, irrespective of the level of susceptibility. High expression of GalNAc residues was observed using soybean lectin labeling, indicating a direct relationship between the glycosylation pattern and susceptibility to Bt fomulation in the Pelotas population. CONCLUSION: The use of Bt fomulation caused greater alterations in the larval intestinal histophysiology compared to the use of XenTari® . © 2018 Society of Chemical Industry.

Selection of a protein solubilization method suitable for phytopathogenic bacteria: a proteomics approach.

BACKGROUND: Finding the best extraction method of proteins from lysed cells is the key step for detection and identification in all proteomics applications. These are important to complement the knowledge about the mechanisms of interaction between plants and phytopathogens causing major economic losses. To develop an optimized extraction protocol, strains of Acidovorax citrulli, Pectobacterium carotovorum subsp. carotovorum and Ralstonia solanacearum were used as representative cells in the study of phytopathogenic bacteria. This study aims to compare four different protein extraction methods, including: Trizol, Phenol, Centrifugation and Lysis in order to determine which are more suitable for proteomic studies using as parameters the quantity and quality of extracted proteins observed in two-dimensional gels. RESULTS: The bacteria studied showed different results among the tested methods. The Lysis method was more efficient for P. carotovorum subsp. carotovorum and R. solanacearum phytobacteria, as well as simple and fast, while for A. citrulli, the Centrifugation method was the best. This evaluation is based on results obtained in polyacrylamide gels that presented a greater abundance of spots and clearer and more consistent strips as detected by two-dimensional gels. CONCLUSIONS: These results attest to the adequacy of these proteins extraction methods for proteomic studies.