Medfly promoters relevant to the sterile insect technique

Identification and expression profiling of Ceratitis capitata genes coding for β-hexosaminidases

The goal of this study was to identify the genes coding for β-N-acetylhexosaminidases in the Mediterranean fruit fly (medfly) Ceratitis capitata, one of the most destructive agricultural pests, belonging to the Tephritidae family, order Diptera. Two dimeric β-N-acetylhexosaminidases, HEXA and HEXB, have been recently identified on Drosophila sperm. These enzymes are involved in egg binding through interactions with complementary carbohydrates on the surface of the egg shell. Three genes, Hexosaminidase 1 (Hexo1), Hexosaminidase 2 (Hexo2) and fused lobes (fdl), encode for HEXA and HEXB subunits. The availability of C. capitata EST libraries derived from embryos and adult heads allowed us to identify three sequences homologous to the D. melanogaster Hexo1, Hexo2 and fdl genes. Here, we report the expression profile analysis of CcHexo1, CcHexo2 and Ccfdld in several tissues, organs and stages. Ccfdl expression was highest in heads of both sexes and in whole adult females. In the testis and ovary the three genes showed distinct spatial and temporal expression patterns. All the mRNAs were detectable in early stages of spermatogenesis; CcHexo2 and Ccfdl were also expressed in early elongating spermatid cysts. All three genes are expressed in the ovarian nurse cells. CcHexo1 and Ccfdl are stage specific, since they have been observed in stages 12 and 13 during oocyte growth, when programmed cell death occurs in nurse cells. The expression pattern of the three genes in medfly gonads suggests that, as their Drosophila counterparts, they may encode for proteins involved in gametogenesis and fertilization.

Two hsp23 genes in the Mediterranean fruit fly, Ceratitis capitata: structural characterization, heat shock regulation and developmental expression

In the present study, we characterized a 3320-bp genomic DNA fragment encoding two medfly (Ceratitis capitata) homologues of the Drosophila melanogaster heat shock protein 23 (hsp23) gene, named Cchsp23-alphaand -beta. The two medfly hsp23 genes are transcribed in opposite directions and encode two almost identical proteins. Furthermore, the two genes exhibit a very high degree of similarity in their 5' untranslated and proximal promoter regions. Phylogenetic analysis indicated that the CcHsp23 proteins are orthologous to Drosophila Hsp23 and Sarcophaga crassipalpis Hsp23. Structural analysis of the 5' flanking regions of the Cchsp23 genes revealed the presence of several putative heat shock elements. Both CcHsp23 genes are induced by heat in a similar manner. In addition to heat-induction, the Cchsp23 genes are expressed at several stages of normal development as well as in ovaries and testes. In general, the developmental expression patterns of the medfly genes are similar, suggesting that they are under similar regulatory mechanisms. However, the expression of the Cchsp23 genes differs significantly from the expression of the Drosophila hsp23 gene in certain embryonic and larval stages, suggesting differential regulation of the hsp23 genes in the two dipteran species. The expression of both Cchsp23 genes in adult flies is increased with age, especially in males.

The heat shock 70 genes of the olive pest Bactrocera oleae: genomic organization and molecular characterization of a transcription unit and its proximal promoter region

A Bactrocera oleae genomic library was constructed and several genomic clones bearing hsp70 sequences were isolated. All clones were in situ hybridized on the major heat shock puff locus of the salivary gland polytene chromosomes. Restriction mapping of the isolated clones and genomic Southern hybridization indicated the presence of several putative hsp70 genes organized in a single cluster. Sequence analysis of an hsp70 transcription unit revealed a single 1905 nt long open reading frame that exhibits characteristic features of the inducible members of the HSP70 family. The presence and organization of many typical binding sites for the Heat Shock and GAGA factors suggest that the promoter of this gene is highly heat-inducible and could be used for conditional expression in transformation systems.

cDNA cloning, heat shock regulation and developmental expression of the hsp83 gene in the Mediterranean fruit fly Ceratitis capitata

This report presents the cDNA cloning, heat shock regulation and developmental expression of the hsp90 gene homologue of the Mediterranean fruit fly Ceratitis capitata (medfly). The isolated cDNA contained the coding region, the 3'UTR and most of the 5'UTR of the medfly hsp90 homologue, which was named Cchsp83. The deduced CcHSP83 polypeptide contained all the highly conserved amino acid segments that characterize the cytosolic members of the HSP90 family. Genomic analysis showed that the Cchsp83 gene is unique and was mapped at the 94C division of the sixth polytene chromosome. The size of the Cchsp83 mRNA was found to be approximately 2.7 kb. The predicted molecular mass of the CcHSP83 protein was 81.4 kDa, while the apparent molecular weight estimated by SDS-PAGE was approximately 90 kDa. Phylogenetic analysis based on 14 insect HSP90 amino acid sequences was consistent with the known phylogeny at low taxonomic level. The Cchsp83 gene is constitutively expressed in all stages of medfly development and is induced from a low level to several-fold by heat, depending on the developmental stage. Heat shock induction begins at 30 degrees C, reaching a maximum between 35 and 41 degrees C. Cchsp83 RNA expression is highly regulated during embryonic development; however, the temporal fluctuations in RNA levels during embryogenesis were not followed by similar fluctuations in the levels of the protein.

Evaluation of the activities of the medfly and Drosophila hsp70 promoters in vivo in germ-line transformed medflies

The promoter of the hsp70 gene of Drosophila melanogaster has been widely used for the expression of foreign genes in other insects. It has been generally assumed that because this gene is highly conserved, its promoter will function efficiently in other species. We report the results of a quantitative comparison of the activities of the medfly and D. melanogaster hsp70 promoters in vivo in transformed medflies. We constructed transformed lines containing the lacZ reporter gene under the control of the two promoters by using Minos-mediated germ-line transformation. The activity of each promoter was evaluated in 15 transformed lines by beta-galactosidase quantitative assays. The heat-inducible activity of the medfly promoter was found several times higher than the respective activity of the heterologous D. melanogaster promoter. These results were confirmed by northern blot analysis and indicate that the D. melanogaster promoter does not work efficiently in medfly. The -263/+105 medfly promoter region that was used in this study was found able to drive heat shock expression of the lacZ reporter gene in all stages of medfly, except early embryonic stages, in a similar fashion to the endogenous hsp70 genes. However the heat inducible RNA levels driven from this promoter region were significantly lower than the endogenous hsp70 RNA levels, suggesting that additional upstream and/or downstream sequences to the -263/+105 region may be necessary for optimum function of the medfly hsp70 promoter in vivo.

Cloning, characterization, and developmental expression of the ribosomal protein S21 gene of the Mediterranean fruit fly Ceratitis capitata

Ribosomal protein S21 (RpS21) belongs to a small group of ribosomal or ribosome-associated proteins. Mutations in the RpS21 gene cause dominant Minute and recessive lethal tumorous phenotypes in Drosophila melanogaster. Studies in several organisms suggest that RpS21 is involved in the regulation of protein synthesis and cell growth. In this report, we used an RT-PCR fragment of D. melanogaster RpS21 mRNA to clone a RpS21 cDNA from the Mediterranean fruit fly, Ceratitis capitata. The isolated cDNA contained both 5' and 3' untranslated regions, and encoded a polypeptide of 83 amino acids with a predicted molecular mass of 9.1 kDa. The deduced protein sequence showed 91% amino acid identity to D. melanogaster RpS21 and strong homology with all known ribosomal S21 proteins. DNA blot hybridization indicated the existence of a single RpS21 gene in the Ceratitis capitata genome. Analysis of the 5' untranslated region revealed the occurrence of a major oligopyrimidine tract at the 5' end, which characterizes most mRNAs undergoing a growth-dependent translational control. Study of the mRNA patterns during development suggested that the expression of Ceratitis RpS21 is temporally regulated at the level of transcription.