Acetylcholinesterase (AChE), encoded by the ace gene, is a key enzyme of cholinergic neurotransmission. Insensitive acetylcholinesterase (AChE) has been shown to be responsible for resistance to OPs and CBs in a number of arthropod species, including the most important pest of olives trees, the olive fruit fly Bactrocera oleae. In this paper, the organization of the B. oleae ace locus, as well as the structural and functional features of the enzyme, are determined. The organization of the gene was deduced by comparison to the ace cDNA sequence of B. oleae and the organization of the locus in Drosophila melanogaster. A similar structure between insect ace gene has been found, with conserved exon-intron positions and junction sequences. The B. oleae ace locus extends for at least 75 kb, consists of ten exons with nine introns and is mapped to division 34 of the chromosome arm IIL. Moreover, according to bioinformatic analysis, the Bo AChE exhibits all the common features of the insect AChE. Such structural and functional similarity among closely related AChE enzymes may implicate similarities in insecticide resistance mechanisms.

In the present study the gp63 gene locus was used as a target for genetic characterization of Leishmania parasites by 2 methods: (i) RFLP analysis with several restriction enzymes (gp63–RFLP), and (ii) intra-genic PCR amplification coupled with restriction analysis (PCR–RFLP). Both methods were applied to a large number of natural isolates belonging to 4 species of the subgenus Viannia, namely L. (V.) braziliensis, L. (V.) peruviana, L. (V.) guyanensis and L. (V.) lainsoni: reference stocks of subgenus Leishmania were included as outgroups. Multilocus isoenzyme typing (MLEE) was used as a reference. On the one hand gp63–RFLP evidenced an extensive polymorphism and revealed specific markers for subgenus, species and geographical populations: congruence with MLEE was demonstrated statistically. The particular interest of gp63–RFLP was illustrated by infra-specific polymorphism, because of the possible relationship with phenotype diversity. On the other hand intra-genic amplification was less resolutive than gp63–RFLP, but also allowed discrimination of the 2 subgenera (PCR alone) and all the species tested in the subgenus Viannia (PCR–RFLP). PCR–RFLP presents an important operational advantage as it allows genetic characterization of minute amounts of parasites, using Leishmania specific primers. The polymorphism revealed by gp63–RFLP and PCR–RFLP illustrates the very high genomic and genetic plasticity of gp63 genes.