In insects, rapidly evolving primary sex-determining signals are transduced by a conserved regulatory module controlling sexual differentiation. In the agricultural pest Ceratitis capitata (Mediterranean fruit fly, or Medfly), we identified a Y-linked gene, Maleness-on-the-Y (MoY), encoding a small protein that is necessary and sufficient for male development. Silencing or disruption of MoY in XY embryos causes feminization, whereas overexpression of MoY in XX embryos induces masculinization. Crosses between transformed XY females and XX males give rise to males and females, indicating that a Y chromosome can be transmitted by XY females. MoY is Y-linked and functionally conserved in other species of the Tephritidae family, highlighting its potential to serve as a tool for developing more effective control strategies against these major agricultural insect pests.

The observed resistance increase was associated with spinosad applications in the respective areas. These values are relatively low and do not yet pose a serious control problem in the field. However, the observed variation documents that spinosad tolerance has increased in areas where the insecticide has been more extensively used.

Cytogenetics of Tephritidae has contributed for more than 30 years to the efficient control of pest members of this family and the species delimitation among them. The sterile insect technique (SIT) is a species-specific and environmentally friendly method for the population control of insect pest species, always as a component of integrated pest management approaches. The construction of polytene chromosome maps facilitated the development, characterization, and improvement of genetic sexing strains, which have boosted the effectiveness of SIT and are considered as models for developing genetic sexing methodologies in other target species. In parallel, characterization of mitotic karyotypes and the availability of polytene chromosomes in Diptera have been and are being used as supplementary evidence in taxonomic studies. Lately, under the common understanding that speciation can be achieved via various pathways and under the umbrella of integrative taxonomy, cytogenetic studies have contributed to multidisciplinary taxonomic approaches. Such studies can shed light on the borders between closely related species and/or incipient speciation, and this is crucial both for the implementation of SIT and the revision/improvement of quarantine policies. In this review, we summarize the cytogenetic status of Tephritidae and discuss the contribution of cytogenetics to the development of genetic sexing strains in this family.

In insects, rapidly evolving primary sex-determining signals are transduced by a conserved regulatory module producing sex-specific proteins that direct sex determination and sexual differentiation 1-4 . In the agricultural pest Ceratitis capitata (medfly), a Y-linked maleness factor (M) is thought to repress the autoregulatory splicing of transformer (Cctra), which is required in XX individuals to establish and maintain female sex determination 5,6 . Despite previous attempts of isolating Y-linked genes using the medfly whole genome, the M factor has remained elusive 7 . Here, we report the identification of a Y-linked gene, Maleness-on the-Y (MoY), and show that it encodes a small novel protein which is both necessary and sufficient for medfly male sex determination. Transient silencing of MoY in XY individuals leads to the development of fertile females while transient expression of MoY in XX individuals results in fertile males. Notably, a cross between these sex reverted individuals gives rise to both fertile males and females indicating that a functional MoY can be maternally transmitted. In contrast to the diversity of M factors found in dipteran species 8-11 , we discovered MoY orthologues in seven other Tephritid species spanning ~111 millions of years of evolution (Mya). We confirmed their male determining function in the olive fly (Bactrocera oleae) and the oriental fruit fly (Bactrocera dorsalis). This unexpected conservation of the primary MoY signal in a large number of important agricultural pests 12will facilitate the development of transferable genetic control strategies in these species, for example sterile male releases or sex-ratio-distorting gene drives.

The olive fruit fly, Bactrocera oleae, is the major pest of the olive tree. Despite its importance, very little genetic and molecular knowledge is available. The present study is a first attempt to identify and characterize B. oleae expressed sequence tags (ESTs). One hundred and ninety-five randomly selected cDNA clones were isolated and the obtained sequences were annotated through BLASTX similarity searches. A set of 159 unique putative transcripts were functionally assigned using Gene Ontology terms in broad categories of biological process, molecular function and cellular component based on D. melanogaster matches. Moreover, the cytogenetic location of 35 ESTs was determined by in situ hybridization to B. oleae polytene chromosomes. The resulting low-resolution EST map more than doubles the available entry points to the insect's genome and can assist syntenic comparisons with other distant species. The deduced codon usage of the isolated ESTs suggested a conserved pattern of B. oleae with its closest relatives. Additionally, the comparative analysis of B. oleae ESTs with the homologous D. melanogaster genes led to the development of 17 nuclear EPIC-PCR markers for the amplification of intron sequences of 11 Tephritidae species. Sequencing analysis of several cross-amplified intron sequences revealed a high degree of conservation among Bactrocera species and a varying transferability of the generated markers across the examined genera, suggesting that this method can provide a useful tool for the clarification of phylogenetic relationships among different species, particularly in cases of species complexes.