Male moths detect sex pheromones emitted by conspecific females with high sensitivity and specificity by the olfactory sensilla on their antennae. Pheromone binding proteins (PBPs) are highly enriched in the sensillum lymph of pheromone sensitive olfactory sensilla and are supposed to contribute to the sensitivity and selectivity of pheromone detection in moths. However, the functional role of PBPs in moth sex pheromone detection in vivo remains obscure. In the silkmoth, Bombyx mori, female moths emit bombykol as a single attractive sex pheromone component along with a small amount of bombykal that negatively modulates the behavioural responses to bombykol. A pair of olfactory receptor neurons, specifically tuned to bombykol or bombykal, co-localise in the trichodeum sensilla, the sensillum lymph of which contains a single PBP, namely, BmPBP1. We analysed the roles of BmPBP1 using BmPBP1-knockout silkmoth lines generated by transcription activator-like effector nuclease-mediated gene targeting. Electroantennogram analysis revealed that the peak response amplitudes of BmPBP1-knockout male antennae to bombykol and bombykal were significantly reduced by a similar percentage when compared with those of the wild-type males. Our results indicate that BmPBP1 plays a crucial role in enhancing the sensitivity, but not the selectivity, of sex pheromone detection in silkmoths.

No abstract

No abstract

No abstract

No abstract

No abstract

Propionate oxidation in Pelotomaculum thermopropionicum is performed under a thermodynamic limit. The most energetically unfavorable reaction in the propionate oxidation pathway is succinate oxidation. Based on previous genomic and transcriptomic analyses, succinate oxidation in P. thermopropionicum under propionate-oxidizing conditions is conducted by the membrane-bound forms of two succinate dehydrogenases (SDHs). We herein examined the activity of SDH, the mechanisms underlying the succinate oxidation reaction in P. thermopropionicum, and the importance of the protein sequences of related genes. SDH activity was highly localized to the membrane fraction. An analysis of the soluble fraction revealed that fumarate reductase received electrons from NADH, suggesting the involvement of membranebound SDH in propionate oxidation. We utilized an uncoupler and inhibitors of adenosine triphosphate (ATP) synthase and membrane-bound SDH to investigate whether the membrane potential of P. thermopropionicum supports propionate oxidation alongside hydrogen production. These chemicals inhibited hydrogen production, indicating that membrane-bound SDH requires a membrane potential for succinate oxidation, and this membrane potential is maintained by ATP synthase. In addition, the phylogenetic distribution of the flavin adenine dinucleotide-binding subunit and conserved amino acid sequences of the cytochrome b subunit of SDHs in propionate-oxidizing bacteria suggests that membrane-bound SDHs possess specific conserved amino acid residues that are strongly associated with efficient succinate oxidation in syntrophic propionate-oxidizing bacteria.

Male moths are capable of orienting towards conspecific females using sex pheromones. Since pheromones are distributed as discontinuous plumes owing to air turbulence, tracking intermittent stimuli with high temporal resolution is suggested to be important for efficient localisation. Here, using a pheromone binding protein (BmPBP1) knockout silkmoth, we revealed that the loss of functional pheromone binding protein altered antennal response kinetics resulting in reduced temporal resolution to intermittent pheromone stimuli on the antennae. Behavioural analysis revealed that BmPBP1-knockout males exhibited significantly less straight walking, which occurs when detecting pheromone stimuli, especially to high frequency stimuli. Accordingly, BmPBP1-knockout males took a significantly longer time to locate pheromone sources and females than did wild-type males. Together, BmPBP1 plays a critical role in determining temporal antennal response kinetics and that an appropriate range of temporal sensory and behavioural resolutions is essential for tracking pheromone plumes for efficient pheromone source localisation in the silkmoth.