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.

Four phospholipase A2 genes encoded in the western flower thrips genome and their functional differentiation in mediating development and immunity

“…In Drosophila melanogaster and S. exigua , PGE 2 was shown to mediate nurse cell dumping during early vitellogenesis in the polytrophic ovarioles 37 , 38 . In F. occidentalis , PGE 2 was detected in growing ovarian follicles by an immunofluorescence assay, and aspirin (a specific cyclooxygenase inhibitor) treatment significantly suppressed the oocyte development in previtellogenesis and choriogenesis 39 . The present study suggests that Fo-PLA 2 A may play a crucial role in the production of PGE 2 in the ovary to facilitate the oocyte development in F. occidentalis .…”

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 .…”

Gene redundancy and gene compensation of insulin-like peptides in the oocyte development of bean beetle

“…At the same time, ILPs are expressed in the midgut, imaginal discs, salivary glands, ovary, and fat body [7][8][9][10]. They are involved in many physiological processes, including cell cycle, development, metabolism, feeding behavior, reproduction, stress resistance, diapause, aging, lifespan, and immunity [2,3,6,[11][12][13]. Most of the knowledge about ILPs comes from D. melanogaster [2].…”