Programmed cell death of follicular epithelium during the late developmental stages of oogenesis in the fruit flies Bactrocera oleae and Ceratitis capitata (Diptera, Tephritidae) is mediated by autophagy

Abstract

In the present study, we describe the features of programmed cell death of ovarian follicle cells, occurring during the late developmental stages of oogenesis in the olive fruit fly, Bactrocera oleae and the medfly, Ceratitis capitata. During stage 14, the follicle cells contain autophagic vacuoles, and they do not exhibit caspase activity in all parts of the egg chamber. Their nuclei are characterized by condensed chromatin, accompanied with high- but not low-molecular weight DNA fragmentation events exclusively detected in distinct cells of the anterior pole. These data argue for the presence of an autophagy-mediated cell death program in the ovarian follicle cell layer in both species. The above results are likely associated with the abundant phagocytosis observed at the entry of the lateral oviducts, where numerous cell bodies are massively engulfed by epithelial cells. We strongly believe that during the termination of the above Dipteran oogenesis, an efficient mechanism of absorption of the degenerated follicle cells is selectively activated, in order to prevent the blockage of the ovarioles and thus robustly support the physiological completion of the ovulation process.