Transcriptome analysis of female western flower thrips, Frankliniella occidentalis, exhibiting neo-panoistic ovarian development

Abstract

The western flower thrips, Frankliniella occidentalis, is one of the most devastating insect pests with explosive reproductive potential. However, its reproductive physiological processes are not well understood. This study reports the ovarian development and associated transcriptomes of F. occidentalis. Each ovary consisted of four ovarioles, each of which contained a maximum of nine follicles in the vitellarium. The germarium consisted of several dividing cells forming a germ cell cluster, presumably consisting of oocytes and nurse cells. The nurse cells were restricted to the germarium while the subsequent follicles did not possess nurse cells or a nutritive cord, supporting the neo-panoistic ovariole usually found in thysanopteran insects. Oocyte development was completed 72 h after adult emergence (AAE). Transcriptome analysis was performed at mid (36 h AAE) and late (60 h AAE) ovarian developmental stages using RNA sequencing (RNASeq) technology. More than 120 million reads per replication were matched to ≈ 15,000 F. occidentalis genes. Almost 500 genes were differentially expressed at each of the mid and late ovarian developmental stages. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that these differentially expressed genes (DEGs) were associated with metabolic pathways along with protein and nucleic acid biosynthesis. In both ovarian developmental stages, vitellogenin, mucin, and chorion genes were highly (> 8-fold) expressed. Endocrine signals associated with ovarian development were further investigated from the DEGs. Insulin and juvenile hormone signals were upregulated only at 36 h AAE, whereas the ecdysteroid signal was highly maintained at 60 h AAE. This study reports the transcriptome associated with the ovarian development of F. occidentalis, which possesses a neo-panoistic ovariole.

Insulin-like Peptides of the Western Flower Thrips Frankliniella occidentalis and Their Mediation of Immature Development

“…In considering multiple ILP s in insects, additional ILP s were predicted in F. occidentalis . For example, an ILP dissimilar to Fo-ILP1 and Fo-ILP2 was reported in the adult stage and inducible by ovarian development [ 35 ]. This suggests additional ILP s may be involved in the growth and development of F. occidentalis .…”

A push-pull strategy to control the western flower thrips, Frankliniella occidentalis, using alarm and aggregation pheromones

“…Different reproductive modes along with a short lifecycle allow the thrips population to rapidly increase during early and late seasons, in which female progeny develop from fertilized eggs while males develop from unfertilized eggs [11,12]. The nutrient-based oogenesis of F. occidentalis is well-programmed in females by gonadotropic hormones including juvenile hormone, ecdysone, and prostaglandin [13,14]. To suppress thrips outbreaks, more than 20 kinds of chemical insecticides including organophosphate, carbamate, pyrethroids, neonicotinoids, avermectin, and spinosad are registered and applied to different agricultural crops [15].…”