title: Identification of a novel hemolymph peptide that modulates silkworm feeding motivation.
abstract: Phytophagous insects do not constantly chew their diets; most of their time is spent in a non-feeding quiescent state even though they live on or around their diets. Following starvation, phytophagous insect larvae exhibit enhanced foraging behaviors such as nibbling and walking similar to the sequential behavior that occurs prior to each meal. Although extensive physiological studies have revealed regularly occurring feeding behaviors in phytophagous insects, little has been elucidated regarding the mechanism at the molecular level. Here, we report identification and characterization of a novel 62-amino acid peptide, designated as hemolymph major anionic peptide (HemaP), from the hemolymph of Bombyx mori larvae that induces foraging behaviors. The endogenous HemaP levels are significantly increased by diet deprivation, whereas refeeding after starvation returns them to basal levels. In larvae fed ad libitum, hemolymph HemaP levels fluctuate according to the feeding cycle, indicating that locomotor-associated feeding behaviors of B. mori larvae are initiated when HemaP levels exceed an unidentified threshold. Furthermore, administration of exogenous HemaP mimics the starvation-experienced state by affecting dopamine levels in the suboesophageal ganglion, which coordinates neck and mandible movements. These data strongly suggest that fluctuation of hemolymph HemaP levels modulates the regularly occurring feeding-motivated behavior in B. mori by triggering feeding initiation.
authors.affiliation: Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan. anagashi@mail.ecc.u-tokyo.ac.jp
authors.forename: Shinji
authors.initials: S
authors.lastname: Nagata
authors.forename: Nobukatsu
authors.initials: N
authors.lastname: Morooka
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Asaoka
authors.forename: Hiromichi
authors.initials: H
authors.lastname: Nagasawa
mesh_terms: D000818:Animals; D001679:Biogenic Amines / Q000378:metabolism; D012831:Bombyx / Q000254:growth & development / Q000502:physiology*; D005247:Feeding Behavior / Q000502:physiology*; D017952:Ganglia, Invertebrate / Q000502:physiology; D006458:Hemolymph / Q000378:metabolism*; D019476:Insect Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D007814:Larva / Q000502:physiology; D009042:Motivation / Q000502:physiology; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D001679:Biogenic Amines; D019476:Insect Proteins; D011994:Recombinant Proteins