title: Isotope label-aided mass spectrometry reveals the influence of environmental factors on metabolism in single eggs of fruit fly.
abstract: In order to investigate the influence of light/dark cycle on the biosynthesis of metabolites during oogenesis, here we demonstrate a simple experimental protocol which combines in-vivo isotopic labeling of primary metabolites with mass spectrometric analysis of single eggs of fruit fly (Drosophila melanogaster). First, fruit flies were adapted to light/dark cycle using artificial white light. Second, female flies were incubated with an isotopically labeled sugar ((13)C(6)-glucose) for 12 h--either during the circadian day or the circadian night, at light or at dark. Third, eggs were obtained from the incubated female flies, and analyzed individually by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS): this yielded information about the extent of labeling with carbon-13. Since the incorporation of carbon-13 to uridine diphosphate glucose (UDP-glucose) in fruit fly eggs is very fast, the labeling of this metabolite was used as an indicator of the biosynthesis of metabolites flies/eggs during 12-h periods, which correspond to circadian day or circadian night. The results reveal that once the flies adapted to the 12-h-light/12-h-dark cycle, the incorporation of carbon-13 to UDP-glucose present in fruit fly eggs was not markedly altered by an acute perturbation to this cycle. This effect may be due to a relationship between biosynthesis of primary metabolites in developing eggs and an alteration to the intake of the labeled substrate - possibly related to the change of the feeding habit. Overall, the study shows the possibility of using MALDI-MS in conjunction with isotopic labeling of small metazoans to unravel the influence of environmental cues on primary metabolism.
authors.affiliation: Department of Applied Chemistry, National Chiao Tung University, Hsinchu, Taiwan.
authors.forename: Te-Wei
authors.initials: TW
authors.lastname: Tseng
authors.forename: June-Tai
authors.initials: JT
authors.lastname: Wu
authors.forename: Yu-Chie
authors.initials: YC
authors.lastname: Chen
authors.forename: Pawel L
authors.initials: PL
authors.lastname: Urban
mesh_terms: D000818:Animals; D002247:Carbon Isotopes; D002940:Circadian Rhythm / Q000528:radiation effects; D004331:Drosophila melanogaster / Q000378:metabolism* / Q000528:radiation effects; D005260:Female; D005947:Glucose / Q000378:metabolism*; D007553:Isotope Labeling; D008027:Light; D010063:Ovum / Q000378:metabolism* / Q000528:radiation effects; D017440:Photoperiod; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods; D014532:Uridine Diphosphate Glucose / Q000032:analysis / Q000096:biosynthesis*
chemical_list: D002247:Carbon Isotopes; D005947:Glucose; D014532:Uridine Diphosphate Glucose