FIGURE 1.

Spontaneous Raman spectra of Drosophila ovaries revealing molecular changes during oogensis. (A) A diagrammatic illustration of the structure of adult ovary. The Drosophila ovary consists of two lobes that are connected by a common oviduct. Each lobe is composited of approximately 14–16 ovarioles. Each ovariole harbors an anterior localized germarium and following older follicles that develop through 14 distinct stages. Within the germarium, germline stem cells (GSCs) are surrounded by cap cells and escort cells, two major cellular components of the somatic niche. One GSC generates two daughter cells through unsymmetric mitosis, one is GSC and the other one is cystoblast. Each cystoblast divides four additional times to form 16-cell germline cysts consisted of nurse cells (nc) and an oocyte (oo). Follicle stem cells (FSC) divide to form prefollicle cells, which surround the 16-cell germline cyst, and isolate them from the germarium. Prefollicle cells give rise to different kinds of specialized follicle cells (fc) that localized in an epithelial monolayer surrounding each cyst. The mature oocyte is localized at the posterior end of each ovariole. The fingerprint region (B) and CH stretching region (C) of mean Raman spectra (n = 10) of follicles at different developmental stages in 5-day female flies. (B) Compared with the mature oocyte, germarium and the developing follicles show a relatively high intensity of Raman peaks at 780 cm⁻¹, 1,000 cm⁻¹, and 1,580 cm⁻¹ and these peaks show a gradually higher intensity alongside the follicle maturation. There is a shape remodeling of amide III in the last stage of oogenesis (stage 14), which is different from the early stages. (C) A dramatically high intensity at 2,852 cm⁻¹ is shown in stage 14 oocytes and the peak position of stage 14 oocytes at 2,937 cm⁻¹ is relatively left-shifted. (D) The enlarged amide III region and (E) CH stretching region comparing the Raman spectral shape from stage 8 (blue) and stage 14 (red) follicle. Early developing follicles (stage 8) showed more protein enriched, and mature eggs (stage 14) showed more likely lipid dominated.