Heat induced male sterility inDrosophila melanogaster: adaptive genetic variations among geographic populations and role of the Y chromosome

Abstract

We analyzed genetic variation among geographically diverse populations of Drosophila and showed that tropical flies are more tolerant than temperate ones to heat-induced male sterility, as assessed by the presence of both motile sperm and progeny production. In tropical populations, the temperature inducing 50% sterility (median threshold) is 1°C above the value for temperate populations (30.4 vs. 29.4°C). When transferred to a mild permissive temperature (21°C), males recover fertility. Recovery time is proportional to pre-adult culture temperature. At these temperatures, recovery time is greater for temperate than for tropical populations. Crosses between a temperate and a tropical strain (F 1, F2and successive backcrosses) revealed that the Y chromosome was responsible for much of the geographic variation. Sterile males exhibited diverse abnormalities in the shape and position of sperm nuclei. However, impairment of the spermatid elongation seems to be the major factor responsible for sperm inviability. Heatinduced male sterility seems to be quite a general phenomenon in Drosophilid species and variation of threshold temperatures may be important for explaining their geographic distributions.

Genome size evolution: Within-species variation in genome size

“…Hence, in addition to changes in centromere composition and whole genome structure, the Y chromosome, because of its highly degenerated heterochromatic state (Charlesworth, 2002) and the fact that it differs in size in different populations, seems to make a particular contribution to the variation in genome size, as reported in some plants (Meagher et al, 2005). This implies that the suggestion that changes in the composition of the Y chromosome could be responsible for geographical adaptive genetic differences between temperate and tropical populations of Drosophila melanogaster (Rohmer et al, 2004) warrants further investigation.…”

Interspecific Y chromosome variation is sufficient to rescue hybrid male sterility and is influenced by the grandparental origin of the chromosomes

“…Instead, most if not all of the~14 protein-coding genes present on the Y chromosomes of Drosophila melanogaster, D. simulans and other closely related species have male-specific functions and are exclusively expressed in the testis (Gepner and Hays, 1993;Carvalho et al, 2000;Carvalho et al, 2001;Vibranovski et al, 2008). Nevertheless, a suite of studies have shown that genetic variation present on the Y of Drosophila underlie phenotypic variation in male fitness (Chippindale and Rice, 2001;Yee et al, 2015), sex ratio distortion (Carvalho et al, 1997;Montchamp-Moreau et al, 2001;Branco et al, 2013a, b), tolerance to temperature extremes (Rohmer et al, 2004;David et al, 2005), behavior (Stoltenberg and Hirsch, 1997;Huttunen and Aspi, 2003), gene expression (Lemos et al, 2008;Sackton et al, 2011;Branco et al, 2013a, b) and chromatin states in somatic tissues .…”

Natural variation of the Y chromosome suppresses sex ratio distortion and modulates testis-specific gene expression in Drosophila simulans

“…The Y chromosome has been shown to regulate organismal traits, such as male fertility (Chippindale and Rice, 2001), sex ratio distortion (Carvalho et al, 1997;Montchamp-Moreau et al, 2001), thermal adaptation (Rohmer et al, 2004) and behaviors (Stoltenberg and Hirsch, 1997;Huttunen and Aspi, 2003). The regulatory bases for these phenotypes have been suggested by genome-wide gene expression studies in D. melanogaster (Lemos et al, 2008Jiang et al, 2010;Paredes et al, 2011).…”