Abstract
Male accessory glands (MAGs) of insects are responsible for the production of many of the seminal fluid proteins and peptides that elicit physiological and behavioral responses in the post-mated female. In the yellow fever mosquito, Aedes aegypti, seminal fluid components are responsible for stimulating egg production, changing female behavior away from host-seeking toward egg-laying and mating refractoriness, but hitherto no behavior-modifying molecule from the MAGs has been structurally characterized. We now show using mass spectrometry and HPLC/ELISA that the MAG is a major site of synthesis of the biologically active decapeptide, Aea-HP-1 (pERPhPSLKTRFamide) that was first characterized by Matsumoto and colleagues in 1989 from mosquito head extracts and shown to have host-seeking inhibitory properties. The peptide is localized to the anterior portion of the MAG, occurs at high concentrations in the gland and is transferred to the female reproductive tract on copulation. Aea-HP-1 has a pyroglutamic acid at the N-terminus, an amidated carboxyl at the C-terminus and an unusual 4-hydroxyproline in position 4 of the peptide. The structure of the peptide with its blocked N- and C-termini confers resistance to metabolic inactivation by MAG peptidases; however the peptide persists for less than 2h in the female reproductive tract after copulation. Aea-HP-1 is not a ligand for the mosquito sex peptide/myoinhibitory peptide receptor. A. aegypti often mate close to the host and therefore it is possible that male-derived Aea-HP-1 induces short-term changes to female host-seeking behavior to reduce potentially lethal encounters with hosts soon after insemination.
Highlights
The mosquito, Aedes aegypti, is the main insect vector of yellow fever, chikungunya fever and dengue fever viruses in tropical and sub-tropical regions of the world [25]
It has been known for a long time that components of seminal fluid made by the male accessory glands (MAGs) and donated to the female during copulation are important for the reproductive success of A. aegypti, by facilitating the safe transfer of sperm, and by directly influencing reproductive physiology and diverse behaviors of the post-mated female, including a lifetime refractoriness to mating [5,6,7,20,29]
We report that the MAGs of A. aegypti are a source of the head peptide Aedes aegypti head peptide (Aea-HP)-1 and that the peptide is transferred during copulation to the female reproductive tract
Summary
The mosquito, Aedes aegypti, is the main insect vector of yellow fever, chikungunya fever and dengue fever viruses in tropical and sub-tropical regions of the world [25]. There is interest in understanding the factors and mechanisms that determine reproductive success and influence behavior of the biting females, to aid the development of new vector control strategies. It has been known for a long time that components of seminal fluid made by the male accessory glands (MAGs) and donated to the female during copulation are important for the reproductive success of A. aegypti, by facilitating the safe transfer of sperm, and by directly influencing reproductive physiology and diverse behaviors of the post-mated female, including a lifetime refractoriness to mating [5,6,7,20,29]. The attempts at purification of active MAG constituents of mosquitoes have been limited to primitive fractionation techniques
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