The distribution of Drosophila albomicans was limited in tropics in Southeast Asia until the mid-1980. Since then, however, the distribution has been extended toward the north to west Japan to date. In our study, we found that the cold tolerance of this species has been improved in the Japanese population with a higher response to cold acclimation. This suggests that improved cold tolerance is attributable to gene expression changes in response to the cold acclimation. Using RNA-seq method, we found many candidate genes responsible for the improvement of cold tolerance. We are trying to identify the causative genes among these genes by artificially modifying gene expression using the GAL4/UAS system in D. melanogaster. [Ref. 1]

Drosophila albomicans has giant X and Y chromosomes named neo-X and neo-Y chromosomes, which originated by fusions of the canonical X and Y chromosomes, respectively, and autosomes corresponding to the third chromosomes in its sister species, D. nasuta. As a result, a large part of the genome has become meiotic-recombination-free. What is the merit of these neo-sex chromosomes? This is a mystery as the meiotic recombination is believed to be evolutionarily advantageous. We are studying to solve this issue. [Ref. 2]

Evolutionary changes of genomic DNA sequences are an ultimate driving force of organismal evolutions. Therefore, it is important to study how DNA sequences change during the evolutionary period for a deep understanding of the evolution of genomes and organisms as well as performing accurate inferring phylogenetic trees and estimating divergence times. We are studying the molecular evolution of genes and genomes, using mathematical modeling, computer simulations, and real data analyses. A special focus is on developing methods for molecular evolutionary and phylogenetic analyses. The current project is to estimate divergence times in a phylogenetic tree in case of unequal evolutionary rates among lineages. [Ref. 3][Ref. 4]

With its theoretical basis firmly established in molecular evolutionary and population genetics, the comparative DNA and protein sequence analyses play a central role in reconstructing the evolutionary histories of species and multigene families, estimating rates of molecular evolution, and inferring the nature and extent of selective forces shaping the evolution of genes and genomes. As a response to the demand for easy-to-use computer programs for such analyses, we have produced Molecular Evolutionary Genetics Analysis (MEGA) software, with its focus on facilitating the exploration and analysis of DNA and protein sequence variations from an evolutionary perspective. [Ref. 5]

The identification of Drosophila species requires high expertise and thus not an easy practice for ordinary researchers. To facilitate this task, we took a bioinformatics approach, focusing on the pattern of wing vein, which is one of the important key characters in traditional taxonomy. Measuring the distances between crossing points of wing veins, we succeeded to identify each species from sixteen Drosophila species commonly observed around Tokyo area. [Ref. 6][Web app.]