Analysis of phenotypes altered by temperature stress and hipermutability in Drosophila willistoni

Marícia F D'Ávila,Vera Lúcia Da S Valente,Rosane N Garcia,Elgion L S Loreto

doi:10.1590/s0073-47212008000300009

Marícia F D'Ávila, Vera Lúcia Da S Valente + Show 2 more

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https://doi.org/10.1590/s0073-47212008000300009

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Abstract

Drosophila willistoni (Sturtevant, 1916) is a species of the willistoni group of Drosophila having wide distribution from the South of USA (Florida) and Mexico to the North of Argentina. It has been subject of many evolutionary studies within the group, due to its considerable ability to successfully occupy a wide range of environments and also because of its great genetic variability expressed by different markers. The D. willistoni 17A2 strain was collected in 1991 in the state of Rio Grande do Sul, Brazil (30°05'S, 51°39'W), and has been maintained since then at the Drosophila laboratory of UFRGS. Different to the other D. willistoni strains maintained in the laboratory, the 17A2 strain spontaneously produced mutant males white-like (white eyes) and sepia-like (brown eyes) in stocks held at 17°C. In order to discover if this strain is potentially hypermutable, we submitted it to temperature stress tests. Eighteen isofemale strains were used in our tests and, after the first generation, all the individuals produced in each strain were maintained at 29°C. Different phenotype alterations were observed in subsequent generations, similar to mutations already well characterized in D. melanogaster (white, sepia, blistered and curly). In addition, an uncommon phenotype alteration with an apparent fusion of the antennae was observed, but only in the isofemale line nº 31. This last alteration has not been previously described as a mutation in the D. melanogaster species. Our results indicate that the D. willistoni 17A2 strain is a candidate for hypermutability, which presents considerable cryptic genetic variability. Different factors may be operating for the formation of this effect, such as the mobilization of transposable elements, effect of inbreeding and alteration of the heat-shock proteins functions.

Highlights

Differing to the findings in the greater part of material collected in natural environments, the 17A2 strain of D. willistoni already presented spontaneous male mutants white-like and sepia-like in stocks, which had been maintained at 17°C in laboratory
Because the species D. willistoni presents extensive genetic variability expressed by various markers such as polymorphism chromosomal for paracentric inversions and enzymatic polymorphism (AYALA & POWELL, 1972), a descriptive investigation such as we present in this study can provide a base for future research, which could lead to a better understanding of the possible causative agents of this D. willistoni genetic variability
The stocks of D. willistoni populations were maintained by general massal crosses in a standard culture medium (MARQUES et al, 1966) inside a chamber kept at a constant temperature of 17°C ± 1°C with approximately 60% relative humidity

Summary

Introduction

The 17A2 strain of Drosophila willistoni Sturtevant, 1916 was collected in 1991 at an agronomic station in Eldorado do Sul, state of Rio Grande do Sul, Brazil (30°05’S, 51°39’W) and since has been maintained in the Drosophila Laboratory of the Department of Genetics at UFRGS (Universidade Federal do Rio Grande do Sul, Brazil). This strain has been used in cytogenetic studies that detected a high level of polymorphism for paracentric chromosomic inversions and male recombination (SANTOS-COLARES et al, 2004). The efforts to establish mutant isostrains were not successful

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