Browsing by Author "Adhikari, Kiran"
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Item Role of Genotype-by-Temperature Interactions in the Maintenance of Polygenic Sex Determination in the House Fly(2021-08) Adhikari, Kiran; Meisel, Richard P.; Frankino, W. Anthony; Tarone, Aaron M.; Zufall, Rebecca A.Sex determination is the process by which sexually dimorphic developmental pathways are established. In genetic sex determination systems, a single master regulatory locus determines the sex of an individual. However, some organisms have multiple master sex determining loci in their genome that segregate independently, resulting in polygenic sex determination. Most population genetics models predict that polygenic sex determination will be an unstable intermediate between monogenic systems, and the factors responsible for maintaining polygenic sex determination are poorly understood. House fly (Musca domestica) has a stable polygenic sex determination system with multiple male and female determiners segregating in natural populations. The male determining gene is commonly found on two different proto-Y chromosomes (YM and IIIM). YM is found in colder, northern latitudes, whereas IIIM is found in southern, warmer latitudes. This suggests that selection operating on a genotype-by-temperature (G×T) interaction maintains this polymorphism. To test this hypothesis, I raised IIIM and YM males with otherwise common genetic backgrounds at high and low temperatures, and I studied the resulting G×T effects on multiple phenotypes. YM males raised at low temperature are more cold tolerant, and IIIM males raised at high temperatures are more heat tolerant, consistent with their distribution in nature. Next, using RNA-seq, I identified 247 genes whose expression in testis and 50 genes whose expression in head depends on GxT interactions. I found G×T effects on the expression of genes on the proto-Y chromosomes other than those in the sex determination pathway. Chemosensory, metabolic, immune, reproductive, and lifespan related genes are differentially expressed because of G×T interactions. Further, using inter-strain and intra-strain mating assays, I found IIIM males have a mating advantage over YM males and males from lower temperatures have a mating advantage over males from higher temperatures. Using a survival assay, I found some differences in lifespan between YM and IIIM males. My results suggest that G×T effects of genes on the proto-Y chromosomes other than the male-determiner are the targets of selection responsible for maintaining polygenic sex determination in house fly, which could be mediated through effects of the proto-Y chromosomes on gene expression. This provides an ecological mechanism to maintain polygenic sex determination.Item The effect of the chromosomal location of the male-determiner on mating success in house fly(2017-10-12) Hassan, Oluwatomi; Trinh, Tammie; Sriskantharajah, Vyshnika; Oderhowho, Alexander; Torres Gonzalez, Jose; Adhikari, KiranSex determination is the molecular process that leads to the development of either a male or a female. Some species are polymorphic for how sex is determined. We do not have a good understanding of why this variation in the initiation of sex determination exists. The house fly, Musca domestica, is a modelorganism for studying the genetics and evolution of polymorphic sex determination. The male-determining Mdmd gene can be found on the Y chromosome (YM) and third chromosome (IIIM). Males carrying IIIM are found in southern regions where average temperatures are warmer. Males with YM are found in northern regions where average temperatures colder. We therefore hypothesize that the IIIM chromosome carries genetic variants that are “warm-beneficial” and YM has “cold-beneficial” variants. Our goal is to determine if there is a temperature-dependent difference in mating success between males with YM and males carrying IIIM. We conclude that male mating success is unlikely to be a trait that explains the geographic distribution of YM and IIIM in natural populations.