Biology subjects

Withall, D. M.

Publications and source records attributed to Withall, D. M..

3 recordsLinked to original sources

bioRxiv2026

Electrostatic facilitation of odorant capture in insects

Olfaction is a sensory modality common to most organisms. In insects, the primary olfactory organ is the antenna, where sensilla house olfactory receptor neurons adapted to detect volatile organic compounds (VOCs). Whilst olfaction is well-understood at molecular and neural levels, questions remain as to how, biophysically, airborne VOCs reach sensilla. Transport through passive diffusion and active antennal motion is empirically supported but cannot entirely explain the remarkably rapid VOC sampling rates. We present evidence that the insect antennae exploits electrostatic forces that amplify VOC transfer from bulk air to sensilla. In effect, charged antennae capture more ambient VOCs than neutral ones, also evoking an enhanced electrophysiological (EAG) response to VOCs. Experimentally altering the charge of isolated antennae modulates EAG responses and olfactory sensitivity. Multiphysics modelling incorporating electrostatic and fluid dynamic mechanisms supports empirical evidence. Altogether, this work reveals the existence of a previously unknown and complementary biophysical mechanism supporting olfaction. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=147 SRC="FIGDIR/small/703773v1_ufig1.gif" ALT="Figure 1"> View larger version (23K): org.highwire.dtl.DTLVardef@1917cc3org.highwire.dtl.DTLVardef@962075org.highwire.dtl.DTLVardef@2ce4b3org.highwire.dtl.DTLVardef@15ada3a_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

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↗