Mobile element 297 in the Abd-B gene of Drosophila melanogaster, not Delta 88, is responsible for the tuh-3 mutation

Variability of esterase patterns in adult flies of the saltans species group of Drosophila (subgenus Sophophora)

Esterases are known for their involvement in several physiological processes and high degree of polymorphism, in many organisms. Such polymorphism has been used to characterize species and species groups and to study genetic changes occurred in their evolutionary history. In the present study, the esterase patterns of 19 strains from 10 species representative of the five subgroups of the saltans species group were analyzed using polyacrylamide gel electrophoresis and alpha- and beta- naphthyl acetates as substrates. Fifty-one esterase bands were detected and classified as 31 alpha-esterases, 18 beta-esterases and two alpha/beta-esterases. On the basis of the inhibition patterns using Malathion and eserine sulfate, 34 bands were classified as carboxylesterases, 14 as acethylesterases and three as cholinesterases. Ten gene loci were tentatively established on the basis of data on band position in the gel, substrate preference and inhibition pattern. Twenty bands were species-specific, the remaining being shared by species from the same or different subgroups. Bands detected exclusively in males and bands with a different frequency or degree of expression between sexes were also detected. In the gels prepared for analysis of gene expression in the body parts (head, thorax and abdomen), the degree of expression of the beta-esterases was higher in the thorax, while the alpha-esterases were expressed predominantly in the abdomen and thorax. A global view of the data available at present on the esterases of the species from the saltans group and their degree of polymorphism are presented, as well as the possibility of using some beta-esterases, because of their characteristics in the gels, as markers for species identification.

Requirement of Abdominal-A and Abdominal-B in the developing genitalia of Drosophila breaks the posterior downregulation rule

The genitalia of Drosophila derive from the genital disc and require the activity of the Abdominal-B (Abd-B) Hox gene. This gene encodes two different proteins, Abd-B M and Abd-B R. We show here that the embryonic genital disc, like the larval genital disc, is formed by cells from the eighth (A8), ninth (A9) and tenth (A10) abdominal segments, which most likely express the Abd-B M, Abd-B R and Caudal products, respectively. Abd-B m is needed for the development of A8 derivatives such as the external and internal female genitalia, the latter also requiring abdominal-A (abd-A), whereas Abd-B r shapes male genitalia (A9 in males). Although Abd-B r represses Abd-B m in the embryo, in at least part of the male A9 such regulation does not occur. In the male A9, some Abd-B m(-)r(-) or Abd-B r(-) clones activate Distal-less and transform part of the genitalia into leg or antenna. In the female A8, many Abd-B m(-)r(-) mutant clones produce similar effects, and also downregulate or eliminate abdominal-A expression. By contrast, although Abd-B m is the main or only Abd-B transcript present in the female A8, Abd-B m(-) clones induced in this primordium do not alter Distal-less or abd-A expression, and transform the A8 segment into the A4. The relationship between Abd-B and abd-A in the female genital disc is opposite to that of the embryonic epidermis, and contravenes the rule that posteriorly expressed Hox genes downregulate more anterior ones.

Genetic and molecular characterization of a noveliab-8regulatory domain in theAbdominal-Bgene ofDrosophila melanogaster

Homeotic (or Hox) genes are key determinants in specifying the anteroposterior axis of most animals. The temporal and spatial expression of these genes requires the presence of large and complex cis-regulatory regions. The Abdominal-B Hox gene of the bithorax complex ofDrosophila is regulated by several infraabdominal domains,which determine Abdominal-B expression in abdominal segments A5 to A9(parasegments 10 to 14). Some of the infraabdominal domains have been characterized, including an infraabdominal-8 domain, which has been located 3′ to the Abdominal-B transcription unit. We have analyzed the expression and mutant phenotype of a P-lacZ element inserted close to the Abdominal-B m origin of transcription and of derivatives of this transposon. Some of these derivatives represent a particular class of mutations in the bithorax complex, because they transform the eighth and ninth abdominal segments without affecting more anterior metameres. The analysis of these mutations and of transformants carrying sequences upstream the Abdominal-B m transcription unit has allowed us to define a new infraabdominal-8 regulatory region, located 5′ to the Abdominal-B transcription unit, and has helped to characterize better the complex regulation of the Abdominal-Bgene.