INTRACELLULAR LOCALIZATION OF KYNURENINE IN THE FATBODY OF DROSOPHILA

Abstract

A B S T R A C TLight blue fluorescent globules accumulate in the cells of the anterior region of the fatbody of Drosophila larvae near the time of pupation. This fluorescent material appears in the Ore-R wild type strain as well as m u t a n t strains in which the synthesis of both the red and brown eye pigments is affected. The vermilion mutant, which is characterized by the absence of the brown pigment component in the eye, was the only strain among those examined which did not develop the light blue fluorescent globules. Utilizing chromatographic techniques together with the information gained by examination of the m u t a n t strains, the fluorescent material has been identified as kynurenine. Of particular interest is the m a n n e r of appearance of the fluorescent material in the vicinity of the nuclear m e m b r a n e of the fat cells.One aspect of tryptophan metabolism in Drosophila is the utilization of this amino acid as a precursor of brown eye pigment. In this biosynthetic pathway the conversion of tryptophan proceeds through formylkynurenine, kynurenine, and 3-hydroxykynurenine. The elucidation of these intermediate compounds in pigment synthesis in Drosophila has been accomplished with the use of eye color mutants, specifically, vermilion (v), cinnabar (cn), and scarlet (st) (2-4, 6, 7, 10, 13).An abnormal appearance of pigment granules in the pupal fat cells characterizes the red cell (re) m u t a n t of Drosophila melanogaster. The type of pigment which accumulates in the fat cells of the rc m u t a n t is related to the brown eye pigment of Drosophila since combination of the rc factor with the v, cn, or st factor will inhibit the development of the rc pigment in the fat cells (9). This pigmentation process can also be restricted by the presence of the melanotic tumor factor, tu w (1 l). However, a period of larval starvation reverses this interference and allows the development of rc pigment in the fat cells of tu~'rc flies to continue.The abnormal formation of brown pigment in the fat cells in the rc strain of Drosophila is particularly interesting since the transplantation studies of Beadle (1) established the fatbody as a source of precursors of brown eye pigment. The rc m u t a n t offers a convenient site, the large pupal fat cells, to study the formation of pigment precursors at the cellular level. Since a n u m b e r of the intermediate biochemicals in the synthesis of brown eye pigment are fluorescent compounds, this reexamination of the fatbody of normal and m u t a n t strains of D. melanogaster utilized the fluorescent microscope.

Genetic Control of Cytodifferentiation

“…The light blue fluorescence characteristic of kynurenine is localized in globular cytoplasmic inclusions in the wild type Ore-R strain. These autofluorescent inclusions are restricted to the cells of the anterior region of the fatbody, and as described previously (21,22) there is a sharp autofluorescent boundary created by the intensity of the kynurenine autofluorescence in these cells in contrast to the autofluorescence of the adjacent cells involved in pteridine metabolism. Under the usual culture conditions no variation in the position of this boundary is noted, and the region of the fatbody containing kynurenine terminates in a row of ceils proceeding ventrocaudad and forming an arc of autofluorescent material when viewed from the lateral aspect.…”

“…The methods used for collecting and raising Drosophila larvae for the present experiments as well as the preparations of cells for fluorcscencc microscopy were the same as those reported previously (21 the anterodorsal region of the fatbody served as the experimental material, and the dorsolateral and the caudal regions of the fatbody were selected as control tissues. Each of the pieces of fatbody was implanted into a 2-day-old vermilion adult male utilizing a micro injection apparatus (19).…”

Cell lineage analysis of kynurenine producing organs inDrosophila melanogaster

“…Since the active substance, v+ or kynurenine, could not be extracted from the fat body, it was concluded that the fat body is capable of kynurenine production. This conclusion was recently corroborated by a more direct approach (Rizki, 1961).…”

Hemolymph Sugar Homeostasis and Starvation-Induced Hyperactivity Affected by Genetic Manipulations of the Adipokinetic Hormone-Encoding Gene in Drosophila melanogaster

“…As however, the overexpression did not alter the trehalose levels ( Figure 5C). This is perhaps because dAkh expresshown in Figure 5F, AKH-CD fat bodies gave rise to background signals originating from endogenous ausion levels are not proportional to the amounts of AKH peptide released; thus, circulating AKH levels in UAStofluorogenic materials in this tissue (Rizki 1961). By comparison, immunofluorescent signals detected in dAkh/ϩ; dAkh-gal4/ϩ animals may approximate those in wild type.…”