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IPD072Aa from Pseudomonas chlororaphis Targets Midgut Epithelial Cells in Killing Western Corn Rootworm ( Diabrotica virgifera virgifera). Appl Environ Microbiol 2023; 89:e0162222. [PMID: 36847510 PMCID: PMC10057879 DOI: 10.1128/aem.01622-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/01/2023] Open
Abstract
IPD072Aa from Pseudomonas chlororaphis is a new insecticidal protein that has been shown to have high activity against western corn rootworm (WCR). IPD072 has no sequence signatures or predicted structural motifs with any known protein revealing little insight into its mode of action using bioinformatic tools. As many bacterially derived insecticidal proteins are known to act through mechanisms that lead to death of midgut cells, we evaluated whether IPD072Aa also acts by targeting the cells of WCR midgut. IPD072Aa exhibits specific binding to brush border membrane vesicles (BBMVs) prepared from WCR guts. The binding was found to occur at binding sites that are different than those recognized by Cry3A or Cry34Ab1/Cry35Ab1, proteins expressed by current maize traits that target WCR. Using fluorescence confocal microscopy, immuno-detection of IPD072Aa in longitudinal sections from whole WCR larvae that were fed IPD072Aa revealed the association of the protein with the cells that line the gut. High-resolution scanning electron microscopy of similar whole larval sections revealed the disruption of the gut lining resulting from cell death caused by IPD072Aa exposure. These data show that the insecticidal activity of IPD072Aa results from specific targeting and killing of rootworm midgut cells. IMPORTANCE Transgenic traits targeting WCR based on insecticidal proteins from Bacillus thuringiensis have proven effective in protecting maize yield in North America. High adoption has led to WCR populations that are resistant to the trait proteins. Four proteins have been developed into commercial traits, but they represent only two modes of action due to cross-resistance among three. New proteins suited for trait development are needed. IPD072Aa, identified from the bacterium Pseudomonas chlororaphis, was shown to be effective in protecting transgenic maize against WCR. To be useful, IPD072Aa must work through binding to different receptors than those utilized by current traits to reduce risk of cross-resistance and understanding its mechanism of toxicity could aid in countering resistance development. Our results show that IPD072Aa binds to receptors in WCR gut that are different than those utilized by current commercial traits and its targeted killing of midgut cells results in larval death.
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Towards Understanding the Function of Aegerolysins. Toxins (Basel) 2022; 14:toxins14090629. [PMID: 36136567 PMCID: PMC9505663 DOI: 10.3390/toxins14090629] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2022] [Revised: 09/04/2022] [Accepted: 09/09/2022] [Indexed: 11/17/2022] Open
Abstract
Aegerolysins are remarkable proteins. They are distributed over the tree of life, being relatively widespread in bacteria and fungi, but also present in some insects, plants, protozoa, and viruses. Despite their abundance in cells of certain developmental stages and their presence in secretomes, only a few aegerolysins have been studied in detail. Their function, in particular, is intriguing. Here, we summarize previously published findings on the distribution, molecular interactions, and function of these versatile aegerolysins. They have very diverse protein sequences but a common fold. The machine learning approach of the AlphaFold2 algorithm, which incorporates physical and biological knowledge of protein structures and multisequence alignments, provides us new insights into the aegerolysins and their pore-forming partners, complemented by additional genomic support. We hypothesize that aegerolysins are involved in the mechanisms of competitive exclusion in the niche.
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Milijaš Jotić M, Panevska A, Iacovache I, Kostanjšek R, Mravinec M, Skočaj M, Zuber B, Pavšič A, Razinger J, Modic Š, Trenti F, Guella G, Sepčić K. Dissecting Out the Molecular Mechanism of Insecticidal Activity of Ostreolysin A6/Pleurotolysin B Complexes on Western Corn Rootworm. Toxins (Basel) 2021; 13:toxins13070455. [PMID: 34209983 PMCID: PMC8310357 DOI: 10.3390/toxins13070455] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Revised: 06/24/2021] [Accepted: 06/25/2021] [Indexed: 02/04/2023] Open
Abstract
Ostreolysin A6 (OlyA6) is a protein produced by the oyster mushroom (Pleurotus ostreatus). It binds to membrane sphingomyelin/cholesterol domains, and together with its protein partner, pleurotolysin B (PlyB), it forms 13-meric transmembrane pore complexes. Further, OlyA6 binds 1000 times more strongly to the insect-specific membrane sphingolipid, ceramide phosphoethanolamine (CPE). In concert with PlyB, OlyA6 has potent and selective insecticidal activity against the western corn rootworm. We analysed the histological alterations of the midgut wall columnar epithelium of western corn rootworm larvae fed with OlyA6/PlyB, which showed vacuolisation of the cell cytoplasm, swelling of the apical cell surface into the gut lumen, and delamination of the basal lamina underlying the epithelium. Additionally, cryo-electron microscopy was used to explore the membrane interactions of the OlyA6/PlyB complex using lipid vesicles composed of artificial lipids containing CPE, and western corn rootworm brush border membrane vesicles. Multimeric transmembrane pores were formed in both vesicle preparations, similar to those described for sphingomyelin/cholesterol membranes. These results strongly suggest that the molecular mechanism of insecticidal action of OlyA6/PlyB arises from specific interactions of OlyA6 with CPE, and the consequent formation of transmembrane pores in the insect midgut.
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Affiliation(s)
- Matej Milijaš Jotić
- Department of Biology, Biotechnical Faculty, University of Ljubljana, 1000 Ljubljana, Slovenia; (M.M.J.); (A.P.); (R.K.); (M.M.); (M.S.); (A.P.)
| | - Anastasija Panevska
- Department of Biology, Biotechnical Faculty, University of Ljubljana, 1000 Ljubljana, Slovenia; (M.M.J.); (A.P.); (R.K.); (M.M.); (M.S.); (A.P.)
| | - Ioan Iacovache
- Institute of Anatomy, University of Bern, 3012 Bern, Switzerland; (I.I.); (B.Z.)
| | - Rok Kostanjšek
- Department of Biology, Biotechnical Faculty, University of Ljubljana, 1000 Ljubljana, Slovenia; (M.M.J.); (A.P.); (R.K.); (M.M.); (M.S.); (A.P.)
| | - Martina Mravinec
- Department of Biology, Biotechnical Faculty, University of Ljubljana, 1000 Ljubljana, Slovenia; (M.M.J.); (A.P.); (R.K.); (M.M.); (M.S.); (A.P.)
| | - Matej Skočaj
- Department of Biology, Biotechnical Faculty, University of Ljubljana, 1000 Ljubljana, Slovenia; (M.M.J.); (A.P.); (R.K.); (M.M.); (M.S.); (A.P.)
| | - Benoît Zuber
- Institute of Anatomy, University of Bern, 3012 Bern, Switzerland; (I.I.); (B.Z.)
| | - Ana Pavšič
- Department of Biology, Biotechnical Faculty, University of Ljubljana, 1000 Ljubljana, Slovenia; (M.M.J.); (A.P.); (R.K.); (M.M.); (M.S.); (A.P.)
| | - Jaka Razinger
- Agricultural Institute of Slovenia, 1000 Ljubljana, Slovenia; (J.R.); (Š.M.)
| | - Špela Modic
- Agricultural Institute of Slovenia, 1000 Ljubljana, Slovenia; (J.R.); (Š.M.)
| | - Francesco Trenti
- Bioorganic Chemistry Laboratory, Department of Physics, University of Trento, 38123 Trento, Italy; (F.T.); (G.G.)
| | - Graziano Guella
- Bioorganic Chemistry Laboratory, Department of Physics, University of Trento, 38123 Trento, Italy; (F.T.); (G.G.)
| | - Kristina Sepčić
- Department of Biology, Biotechnical Faculty, University of Ljubljana, 1000 Ljubljana, Slovenia; (M.M.J.); (A.P.); (R.K.); (M.M.); (M.S.); (A.P.)
- Correspondence: ; Tel.: +386-1-320-3419
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