Biology subjects

Caulfield, J. C.

Publications and source records attributed to Caulfield, J. C..

4 recordsLinked to original sources

bioRxiv2025

Inducible volatile chemical signalling drives antifungal activity of Trichoderma hamatum GD12 during confrontation with the pathogen Sclerotinia sclerotiorum

BACKGROUNDThe use of beneficial soil fungi or their natural products offers a more sustainable alternative to synthetic fungicides for pathogen management in crops. Volatile organic compounds (VOCs) produced by such fungi act as semiochemicals that inhibit pathogens, with VOC production influenced by physical interactions between competing fungi. This study explores the interaction between the beneficial soil fungus Trichoderma hamatum GD12 strain (GD12), previously shown to antagonize crop pathogens such as Sclerotinia sclerotiorum, to test the hypothesis that its antagonistic effect is mediated by volatile chemical signalling. A GD12 mutant deficient in the chitinolytic enzyme N-acetyl-{beta}-glucosaminidase ({Delta}Thnag : : hph), which shows reduced biocontrol activity, was also examined. RESULTSIn dual-culture confrontation assays, co-inoculation of GD12 and S. sclerotiorum led to fungistatic interactions after 7 days, whereas{Delta} Thnag : : hph showed no antagonism, indicating a loss of antagonistic function. VOCs collected from individual and co-cultures were analysed by gas chromatography - flame ionization detector (GC-FID) analysis and coupled GC-mass spectrometry (GC-MS), revealing significant differences in VOC production between treatments, with VOC production notably upregulated in the GD12 + S. sclerotiorum co-culture. Peak production of 6-pentyl-2H-pyran-2-one occurred 17 days post-inoculation. This upregulation was absent in the{Delta} Thnag : : hph co-culture, suggesting VOCs may drive antagonism. Synthetic VOC assays revealed several compounds inhibitory to S. sclerotiorum, including 1-octen-3-one, which also arrested the growth of key fungal pathogens (Botrytis cinerea, Pyrenopeziza brassicae, and Gaeumannomyces tritici). Structural insights into 1-octen-3-ones antifungal activity against S. sclerotiorum are also presented. CONCLUSIONSThese findings support the hypothesis that the antagonistic properties of T. hamatum GD12 against crop fungal pathogens can, in part, be attributed to VOC production. Further research is needed to assess the potential of these semiochemicals as tools for pathogen management in agriculture.

microbiology↗

bioRxiv2024

Characterisation of aphid antixenosis in aphid-resistant ancestor wheat, Triticum monococcum

BACKGROUNDDue to the increasing presence of insecticide resistance across cereal aphid populations, new aphid management strategies, including the engineering of host resistance to aphids into commercial wheat varieties, are required. Previous studies have identified ancestor wheat, Triticum monococcum accessions MDR045 and MDR049, with resistance against the grain aphid, Sitobion avenae. To test the hypothesis that resistance can be accounted for by antixenosis (reduced attractiveness of host plants) via the release of repellent volatile organic compounds (VOCs), we explored the response of S. avenae to MDR045 and MDR049 following S. avenae herbivory, using behaviour and electrophysiology experiments. RESULTSIn four-arm olfactometry assays, alate S. avenae showed aphid-density dependent reduced preference to VOC extracts from T. monococcum MDR045 and MDR049. By contrast, alate S. avenae showed aphid-density dependent increased preference to extracts from hexaploid wheat, T. aestivum var Solstice and T. monococcum MDR037. Coupled gas chromatography-electroantennography (GC- EAG), using the antennae of alate S. avenae, located 24 electrophysiologically active compounds across all tested accessions. Synthetic blends created from 21 identified EAG-active compounds confirmed bioactivity of corresponding VOC extracts in four-arm olfactometry assays against alate S. avenae. CONCLUSIONOur data suggest that resistance of T. monococcum MDR045 and MDR049 to S. avenae can be at least partially accounted for by antixenosis, through antennal perception of specific repellent VOC blends induced by S. avenae feeding behaviour.

ecology↗

bioRxiv2023

Chemical cues from beetle larvae trigger proliferation and virulence of a plant pathogen

Agricultural crop productivity and global forest biomes are coming under increasing threat from insect pests and microbial pathogens. This impact is worsened by inter- kingdom insect-microbe interactions that can increase transmission and disease severity in affected plants. Whilst bacterial chemical cues have been shown to directly influence insect behaviour, the impact of insect-derived compounds on phytopathogens is poorly understood. Here, we investigated the chemical basis for interactions between beetle larvae and bacteria in acute oak decline (AOD), a disease characterised by inner bark necrosis and involving a polymicrobial consortium including Brenneria goodwinii and larval galleries of Agrilus biguttatus. We found that A. biguttatus larval extracts contain chemical elicitors that increase bacterial growth rate and final cell density during in vitro culture, and stimulate the differential expression of [~]600 genes, including the Type III Secretion System and its effectors, which are major virulence factors in plant pathogens. Chemical compounds from closely related insect species did not have this effect. These findings highlight the importance of inter-kingdom interactions in plant disease and suggests a novel mode-of-action for insect-derived chemical elicitors in facilitating the virulence of phytopathogens.

ecology↗

bioRxiv2019

Responses of the putative trachoma vector, Musca sorbens, to volatile semiochemicals from human faeces

BackgroundThe putative vector of trachoma, Musca sorbens, prefers to lay its eggs on human faeces on the ground. This study sought to determine whether M. sorbens females were attracted to volatile odours from human faeces in preference to odours from the faeces of other animals, and to determine whether specific volatile semiochemicals mediate selection of the faeces.\n\nMethodology/Principal findingsTraps baited with the faeces of humans and local domestic animals were used to catch flies at two trachoma-endemic locations in The Gambia and one in Ethiopia. At all locations, traps baited with faeces caught more female M. sorbens than control traps baited with soil, and human faeces was the most successful bait compared with soil (mean rate ratios 44.40, 61.40, 10.50 [P<0.001]; 8.17 for child faeces [P=0.004]). Odours from human faeces and some domestic animals were sampled by air entrainment. Extracts of the volatiles from human faeces were tested by coupled gas chromatography-electroantennography with laboratory-reared female M. sorbens. Twelve compounds were electrophysiologically active and tentatively identified by coupled mass spectrometry-gas chromatography, these included cresol, indole, 2-methylpropanoic acid, butanoic acid, pentanoic acid and hexanoic acid.\n\nConclusions/SignificanceIt is possible that some of these volatiles govern the strong attraction of M. sorbens flies to human faeces. If so, a synthetic blend of these chemicals, at the correct ratios, may prove to be a highly attractive lure. This could be used in odour-baited traps for monitoring or control of this species in trachoma-endemic regions.\n\nAuthor summaryMusca sorbens, also known as the Bazaar Fly, visits peoples faces to feed on ocular and nasal discharge. While feeding, M. sorbens can transmit Chlamydia trachomatis, the bacterium that causes the infectious eye disease trachoma. Around 1.9 million people worldwide are visually impaired or blind from this disease. Although it is believed that M. sorbens transmits trachoma, very few studies have looked at ways to control this fly. A large-scale trial has shown that control of fly populations with insecticide reduces active trachoma disease prevalence. Odour-baited traps for the suppression of disease vector populations are an attractive option as there is no widespread spraying of insecticide, however, highly attractive baits are critical to their success. Here we demonstrate that the preference of these flies for breeding in human faeces is probably mediated by odour cues, and we isolate chemicals in the odour of human faeces that cause a response in the antennae of M. sorbens. These compounds may play a role in the specific attractiveness of human faeces to these flies, perhaps by being present in greater amounts or at favourable ratios. These may be developed into a chemical lure for odour-baited trapping to suppress M. sorbens populations.

ecology↗