Synthesis and secretion of volatile short‐chain fatty acids in Triatoma infestans infected with Beauveria bassiana

• Published in: Medical and veterinary entomology 2018-09, Vol.32 (3), p.358-364
• Main Authors: Lobo, L. S., Girotti, J. R., Mijailovsky, S. J., Fernandes, É. K. K., Luz, C., Pedrini, N.
• Format: Article
• Language: English
• Subjects: Alarm pheromone; Beauveria bassiana; Chagas disease; Chagas' disease vector; Entomopathogenic fungi; Fatty acids; gene expression; Infections; Organic compounds; Polymerase chain reaction; Propionic acid; Secretion; Triatoma infestans; triatomine bugs; VOCs; Volatile organic compounds; Volatiles
• ISSN: 0269-283X; 1365-2915
• DOI: 10.1111/mve.12306

Physically disturbed Triatoma infestans (Hemiptera: Reduviidae) adults, as well as adults of other Chagas' disease vectors, secrete a mix of volatile organic compounds (VOCs) with alarm and possible sexual and defence functions. The aim of the present research was to test whether infection with the entomopathogenic fungus Beauveria bassiana (Ascomycota: Hypocreales: Clavicipitaceae) has an effect on VOC secretion in disturbed T. infestans and on the expression of two genes (Ti‐brnq and Ti‐bckdc) potentially involved in VOC biosynthesis. The volatiles released by insects at different time periods after fungal treatment were identified and their relative amounts measured. Isobutyric acid was the most abundant volatile found in both healthy and fungus‐infected insects and underwent no significant relative changes through the infection process. The secretion of propionic acid, however, was significantly higher at 1–4 days post‐infection (d.p. i.) compared with that in controls. A slight induction of both Ti‐brnq and Ti‐bckdc genes was found by real‐time polymerase chain reaction at 4 d.p. i., with expression values reaching up to three‐fold those in controls. The early stages of fungal infection seem to affect the composition of the alarm pheromone by changing the expression pattern of both genes analysed. These results help to elucidate the impact of fungal infections on the chemical ecology of triatomine bugs. Adults of the Chagas' disease vector Triatoma infestans secrete a mix of volatile organic compounds (VOCs) that have alarm and possible sexual and defence functions when insects are physically disturbed. The potential alterations to insect VOCs caused by infection with the entomopathogenic fungus Beauveria bassiana were analysed. Early stages of fungal infection seem to affect the composition of the alarm pheromone by changing the expression pattern of genes potentially involved in its synthesis.