132 Variations in the heat-induced protein pattern of several Drosophila rnontiurn subgroup species (Diptera: Drosophilidae) Irene Konstantopoulou, Elena Drosopoulou, and Zacharias G. Scouras Abstract: After temperature elevation, the newly synthesized polypeptides from several Drosophila montium subgroup species, ofthe melanogaster species group, were analyzed in denaturing acrylamide gels. The pattern obtained is characteristic ofthe heat shock response already documented for many other Drosophila species, although the relative electrophoretic mobility of the "small" heat shock proteins exhibits a species-specific pattern. Based on the above pattern, the montium species are placed in three distinct groups. The present data is consistent with that previously used to propose a northeast to southwest evolutionary mode of expansion for the montium subgroup species. Key words: heat shock proteins, Drosophila montium subgroup species, evolution. Resume: Les polypeptides synthetises en reponse a une augmentation de la temperature ont ete analyses sur gels de polyacrylamide denaturants chez plusieurs especes du sous-groupe Drosophila montium appartenant au groupe d'especes melanogaster. Les motifs obtenus sont caracteristiques de la reponse au stress thermique deja documentee chez plusieurs autres especes de Drosophila, si ce n'est que la mobilite electrophoretique relative des « petites »proteines de choc thermique semble varier en fonction de I' espece. En fonction des motifs, les especes du groupe montium ont pu etre classifiees en trois groupes distincts. Ces donnees sont en accord avec les resultats anterieurs qui suggeraient un mode d'expansion, au cours de l'evolution, allant du Nord-Est au Sud-Quest pour les especes appartenant au sous-groupe montium. Mots eMs: proteines de choc thermique, especes du sous-groupe Drosophila montium, evolution. [Traduit par la Redaction] Introduction The heat shock response was first described as a new heat- inducible puffing pattern in the salivary gland chromosomes of Drosophila (Ritossa 1962). This puffing pattern is accom- panied by the increased synthesis of a subset of proteins, the so-called heat shock proteins (hsps) (Tissieres et al. 1974; Lewis et al. 1975; Ashburner and Bonner 1979). Hsps are found in all organisms examined to date; they comprise a num- ber of protein families that exhibit a high degree of conserva- tion and can also be induced by other types of stress (Lindquist 1986;Lindquist and Craig 1988; Ozawa et al. 1992; Kaal et al. 1995). In Drosophila melanogaster, the heat shock protein super- family (HSP) includes three major families that are character- ized by their molecular masses and are designated HSP90, HSP70, and the "small" hsps. The HSP90 family is repre- sented by hsp83, which is the product of a single-copy gene (Holmgren et al. 1979). The most prominent member of the Corresponding Editor: AJ. Hilliker. Received September 18, 1996. Accepted November 19, 1996. I. Konstantopoulou, E. Drosopoulou, and Z.G. Scouras.l Department of Genetics, Development and Molecular Biology, School of Biology, Faculty of Science, Aristotle University of Thessaloniki (AUTH), GR-54006 Thessaloniki, Greece. I Author to whom all correspondence should be addressed (e-mail: Scouras@bio.auth.gr). Genome, 40: 132-137 (1997) HSP70 family is hsp70, which is produced by multiple copies of the corresponding gene; other members are the heat- inducible hsp68 and the cognates (hsc70), which are constitu- tively expressed and non-heat-inducible forms of this same family (Pauli et al. 1992). The "small" hsps are represented by four distinct polypeptides of 27, 26, 23, and 22 kiloDaltons (kDa), which are the products of four distinct genes (Corces et al. 1980). It is well established that hsps play a role in cell survival fol- lowing heat shock and other types of environmental stress; like the HSP70 family members, hsp83 and the "small" hsps have also been found to act as molecular chaperones (Schlesinger 1990; Hightower 1991; Parsell and Lindquist 1993), and most recently, to control aspects of cellular ageing in humans (Kaal et al. 1995). Apart from their crucial role under stress conditions, most of the hsps are also synthesized under normal conditions. Hsp83 is constitutively expressed and after heat shock presents moderately increased levels (O'Connor~nd Lis 1981). Similarly, each of the "small" hsps can also be produced under non-stress conditions at certain developmental stages (O'Connor and Lis 1981; Parsell and Lindquist 1993). The montium subgroup is the largest among the 11 sub- groups comprising the melanogaster species group and exhib- its a wide geographical distribution from Northeast Asia, to Australia, Africa, and South America (see Lemeunier et al. (1986) and Ashburner (1989) for recent reviews). The montium species are closely related and have expanded following a northeast to southwest geographical distribution, @1997 NRC Canada