Sniffing Out Chemosensory Genes from the Mediterranean Fruit Fly, Ceratitis capitata

Abstract

The Mediterranean fruit fly, Ceratitis capitata (medfly), is an extremely invasive agricultural pest due to its extremely wide host range and its ability to adapt to a broad range of climatic conditions and habitats. Chemosensory behaviour plays an important role in many crucial stages in the life of this insect, such as the detection of pheromone cues during mate pursuit and odorants during host plant localisation. Thus, the analysis of the chemosensory gene repertoire is an important step for the interpretation of the biology of this species and consequently its invasive potential. Moreover, these genes may represent ideal targets for the development of novel, effective control methods and pest population monitoring systems. Expressed sequence tag libraries from C. capitata adult heads, embryos, male accessory glands and testes were screened for sequences encoding putative odorant binding proteins (OBPs). A total of seventeen putative OBP transcripts were identified, corresponding to 13 Classic, three Minus-C and one Plus-C subfamily OBPs. The tissue distributions of the OBP transcripts were assessed by RT-PCR and a subset of five genes with predicted proteins sharing high sequence similarities and close phylogenetic affinities to Drosophila melanogaster pheromone binding protein related proteins (PBPRPs) were characterised in greater detail. Real Time quantitative PCR was used to assess the effects of maturation, mating and time of day on the transcript abundances of the putative PBPRP genes in the principal olfactory organs, the antennae, in males and females. The results of the present study have facilitated the annotation of OBP genes in the recently released medfly genome sequence and represent a significant contribution to the characterisation of the medfly chemosensory repertoire. The identification of these medfly OBPs/PBPRPs permitted evolutionary and functional comparisons with homologous sequences from other tephritids of the genera Bactrocera and Rhagoletis.

Identification and expression profiles of novel odorant binding proteins and functional analysis of OBP99a in Bactrocera dorsalis

“…OBP44a was found to be abundantly expressed in the pupal stage, which agrees with another study of Anopheles stephensi that reported that AsteObp1 levels peaked in the late pupae stage, which suggests a possible chemosensory role for this gene in pupae, or perhaps a simple correlation with the onset of development of chemosensory tissue during pupation (Sengul & Tu, ). The expression levels of the OBP56d , OBP99a , OBP99c , and OBP19c genes significantly increased in the sexual maturity stage, and similar results were found in C. capitata (Siciliano, Scolari et al., ) . CcapOBP69a, CcapOBP19d‐1, CcapOBP83a‐1 , and Ccap83a‐2 are highly expressed in mature virgins, indicating that females may be dependent on the synthesis of the molecular components required for mate recognition (Siciliano, Scolari et al., ).…”

“…The expression levels of the OBP56d , OBP99a , OBP99c , and OBP19c genes significantly increased in the sexual maturity stage, and similar results were found in C. capitata (Siciliano, Scolari et al., ) . CcapOBP69a, CcapOBP19d‐1, CcapOBP83a‐1 , and Ccap83a‐2 are highly expressed in mature virgins, indicating that females may be dependent on the synthesis of the molecular components required for mate recognition (Siciliano, Scolari et al., ). After mating, the OBP56d , OBP99a , and OBP99c gene expression levels remained high in females, which are also consistent with the results obtained in C. capitate , that is, mated females undergo a dramatic and nearly immediate behavioral switch from male pheromone‐oriented to host fruit‐oriented olfactory behavior for oviposition (Jang, ).…”

“…In Diptera, OBPs have been widely identified and functionally analyzed in model genera, such as Drosophila and Anopheles (Li, Pickett, Field, & Zhou, ; Swarup, Williams, & Anholt, ). Additionally, several OBP s have also been identified in Tephritidae (a family notorious for its extremely wide host range) species such as Anastrepha obliqua and Ceratitis capitata (Nakamura et al., ; Papanicolaou et al., ; Siciliano, He et al., ; Siciliano, Scolari et al., ). However, the roles of these OBP s are largely unknown.…”

TRANSCRIPTOME AND TISSUE‐SPECIFIC EXPRESSION ANALYSIS OF OBP AND CSP GENES IN THE DARK BLACK CHAFER

“…It is now accepted that OBPs contribute to the sensitivity of the olfactory system by transporting odorants through sensillar lymph (Leal, ). Functions of OBPs are being unraveled by biochemical, biophysical, structural biology, and RNA interference studies (Leal et al., ; Biessmann et al., ; Pelletier et al., ; Xu et al., ; Xu et al., ; Siciliano et al., ). Moreover, the roles of additional families of putative olfactory proteins, namely CSPs are emerging (Angeli et al., ).…”

How functional genomics will impact fruit fly pest control: the example of the Mediterranean fruit fly, Ceratitis capitata

“…Three main groups of molecules are involved: odorant-binding proteins (OBPs), chemosensory proteins (CSPs), and the chemoreceptor superfamily formed by the olfactory (OR), gustatory (GR) and ionotropic (IR) receptor families [ 64 , 65 ]. The chemosensory gene repertoire of the medfly is currently being characterized at the functional genomics and structural level [ 40 , 41 ]. So far, one antennal-enriched OBP appears to be particularly promising for practical applications.…”