Regulation of olfactory-based sex behaviors in the silkworm by genes in the sex-determination cascade

Abstract

25Insect courtship and mating depend on integration of olfactory, visual, and tactile cues. 26 Compared to other insects, Bombyx mori, the domesticated silkworm, has relatively 27 simple sexual behaviors as it cannot fly. Here by using CRISPR/Cas and 28 electrophysiological techniques we found that courtship and mating behaviors are 29 regulated in male silk moths by mutating genes in the sex determination cascade 30 belonging to two conserved pathways. Loss of Bmdsx gene expression significantly 31 reduced the peripheral perception of the major pheromone component bombykol by 32 reducing expression of the product of the BmOR1 gene which completely blocked 33 courtship in adult males. Interestingly, we found that mating behavior was regulated 34 independently by another sexual differentiation gene, Bmfru. Loss of Bmfru completely 35 blocked mating, but males displayed normal courtship behavior. Lack of Bmfru 36 expression significantly reduced the perception of the minor pheromone component 37 bombykal due to the down regulation of BmOR3 expression; further, functional analysis 38 revealed that loss of the product of BmOR3 played a key role in terminating male mating 39 behavior. Our results suggest that Bmdsx and Bmfru are at the base of the two primary 40 pathways that regulate olfactory-based sexual behavior. 41 42 genome editing 43 44 45 46 3 47 Author Summary 48 The fundamental insect sexual behaviors, courtship and mating, result from successful 49 integration of olfactory, vision, tactile and other complex innate behaviors. In the widely 50 used insect model, Drosophila melanogaster, the sex determination cascade genes 51 fruitless and doublesex are involved in the regulation of courtship and mating behaviors; 52 however, little is known about the function of these sexual differentiation genes in 53 regulating sex behaviors of Lepidoptera. Here we combine genetics and 54 electrophysiology to investigate regulation pathway of sexual behaviors in the model 55 lepidopteran insect, the domesticated silk moth, Bombyx mori. Our results support the 56 presence of two genetic pathways in B. mori, named Bmdsx-BmOR1-bombykol and 57 Bmfru-BmOR3-bombykal, which control distinct aspects of male sexual behavior that are 58 modulated by olfaction. This is the first comprehensive report about the role of sex 59 differentiation genes in the male sexual behavior in the silk moth.60 61 62 63 64 65 66 67 68 4 69 Introduction 70 Sex determination pathways control the sexually dimorphic traits of males and females, 71 including sexual differentiation and sexual behavior [1]. The genetic cascades of primary 72 signalling that underlie sex determination in insects have high diversity among species. In 73 the model insect Drosophila melanogaster, sex determination is controlled hierarchically 74 by X:A, Sex-lethal (Sxl), transformer or transformer 2 (tra/tra2), doublesex (dsx), and 75 fruitless (fru) [2, 3]. An X:A ratio of 1 promotes transcription of Sxl and results in 76 feminization, while an X:A ratio of 0.5 results in Sxl ...

Fruitless mutant male mosquitoes gain attraction to human odor

“…Only female Aedes aegypti mosquitoes host-seek, and we have shown that mutating fruitless reveals an attraction to human odor in the male mosquito ( Figure 5E). Previously, fruitless was shown to be required for male mating behavior in both Drosophila (Demir and Dickson, 2005) and Bombyx silkmoths (Xu et al, 2020). Our work demonstrates that in Aedes aegypti mosquitoes, fruitless has acquired a novel role in inhibiting female host-seeking behavior in the male ( Figure 5F).…”

fruitlessmutant male mosquitoes gain attraction to human odor

“…3f). Previously, fruitless was shown to be required for male mating behavior in both Drosophila 14 and Bombyx silkmoths 49 . Our work demonstrates that in mosquitoes, fruitless has acquired a novel role in inhibiting female host-seeking behavior in the male (Fig.…”

Protein visualization and manipulation inDrosophilathrough the use of epitope tags recognized by nanobodies

“…NbVHH05 or Nb127D01 were cloned from pHEN6-VHH05 or pHEN6-127D01 (Ploegh lab). GFP was amplified from PXL-IE1-EGFP-nos-Cas9 (Xu et al, 2020). PCR fragments were joined together with the digested pW10 backbone by Gibson assembly.…”