Research Overview

The focus of our laboratory is elucidating the genomic and genetic changes that cause biological evolution on the molecular level. In particular, we look at the mechanisms of environmental adaptation, speciation, and sex chromosome evolution. We do a wide range of work that include field collections, molecular biology experiments, and bioinformatics. 

Our current research themes include the following:

1. Niche exploitation to oviposit into ripening fruits and its consequences to mechanical reproductive isolation (Takahashi Group)
2. Variation and pleiotropic effects of genes involved in body pigmentation (Takahashi Group)
3. Evolution of sex chromosomes (Nozawa Group)
4. Evolution of mRNA-based gene regulatory networks (Nozawa Group)

If you are interested in joining the graduate program and doing research with us, please contact us through email.  

Current Projects

(1) Niche exploitation to oviposit into ripening fruits and its consequences to mechanical reproductive isolation (Takahashi Group)

Unlike many other Drosophila species that lay their eggs on rotting fruit, Drosophila suzukii lay their eggs on fruit that is still on the tree, making it a well-known agricultural pest. In order to be able to break through the hard fruit pericarp, this species has developed an enlarged, saw-like ovipositor tube. Drosophila subpulchrella, a closely related species from Japan, also possess a well-developed ovipositor, but its shape is less straight, and it does not lay eggs in fruits that are as tough as those targeted by D. suzukii. These differences in ovipositor morphology appear to have consequences in genital coupling during mating, which effectively causes mechanical reproductive isolation between these species. To understand the drivers of this differentiation, we have worked on topics such as gene regulatory networks in egg-laying tubes, effects of microbial diversity on oviposition and feeding behaviors, and the dynamics of the union of reproductive organs that result to mechanical reproductive isolation.

(2) Variation and pleiotropic effects of genes involved in body pigmentation (Takahashi Group)

Drosophila melanogaster is a model organism that has been widely used in the laboratory  but can be found in fields around human homes. Some individuals from the wild Drosophila populations appear darker, while others have lighter body pigmentation. Previous research have determined that this phenotypic variation arises from differences in the expression of a gene called ebony before and after hatching. Our current research now centers on this gene, including work on clarifying the role of the an upstream DNA sequence that regulates ebony expression, and studies mutations in genes involved in the pigment biosynthesis system that cause variations in body color.

(3) Evolution of sex chromosomes (Nozawa Group)

Sexual reproduction is the fundamental mechanism of reproduction in eukaryotes and certain prokaryotes, with sex chromosomes playing key roles in governing this process. Sex chromosomes originally evolved from autosomes that acquire sex determination genes. When they form, these new proto-X and proto-Y chromosomes stop recombination to maintain stable sex ratios. However, this also causes the Y chromosome to degenerate by losing genes and acquiring many repetitive elements. We are thus trying to understand this evolutionary process and clarify how organisms with sex chromosomes overcame the involved evolutionary challenges by using a variety of Drosophila stock species.

(4) Evolution of mRNA-based gene regulatory networks (Nozawa Group)

miRNAs, small RNAs made of 21-24 nucleotides, regulate target mRNA in many plants and animals. Using Drosophila as our model system, we are investigating how newly generated miRNAs integrate into existing gene regulatory networks and whether they co-evolve with their target genes. Moreover, we are developing methods to be able to identify miRNA-target gene pairs without relying on bioinformatic predictions. 

Staff Highlight

Dr. Aya Takahashi (高橋文) Professor	Dr. Masafumi Nozawa (野澤昌文) Associate Professor
Email:
ayat[at]tmu.ac.jp	manozawa[at]tmu.ac.jp
Read more:
(Researchgate Profile) (ResearchMap Profile) (TMU Faculty Profile (Japanese)) (Research Website)	(Researchgate Profile) (ResearchMap Profile) (TMU Faculty Profile (Japanese)) (Research Website)
Lab Information: Department Laboratory Page (English) (Japanese)

Recent Publications

1. Effects of heavy-ion beam irradiation on non-model fruit fly, Drosophila miranda: part II. Inducing large deletions to males. 

Nagasawa JA, Ogawa M., Tsuneizumi K., Abe T., Nozawa M. RIKEN Accelerator Progress Report, 57 193-193, Dec 2024

2. Sex chromosome cycle as a mechanism of stable sex determination. 

Shun Hayashi, Takuya Abe, Takeshi Igawa, Yukako Katsura, Yusuke Kazama, Masafumi Nozawa, 

Journal of Biochemistry, 176(2) 81-95, Jul 2024

3. Single-fly assemblies fill major phylogenomic gaps across the Drosophilidae Tree of Life 

Bernard Y. Kim, Hannah R. Gellert, Samuel H. Church, Anton Suvorov, Sean S. Anderson, Olga Barmina, Sofia G. Beskid, 

Aaron A. Comeault, K. Nicole Crown, Sarah E. Diamond, PLoS Biology, 22(7) e3002697, Jul 2024

4. Evolution of sex-biased genes in Drosophila species with neo-sex chromosomes: Potential contribution to reducing the sexual conflict. 

Anika Minovic, Masafumi Nozawa, Ecology and Evolution, 14(7) e11701, Jul 2024

5. Odd-Paired is Involved in Morphological Divergence of Snail-Feeding Beetles 

Junji Konuma, Tomochika Fujisawa, Tomoaki Nishiyama, Masahiro Kasahara, Tomoko F Shibata, Masafumi Nozawa, 

Shuji Shigenobu, Atsushi Toyoda, Mitsuyasu Hasebe, Teiji Sota, Molecular Biology and Evolution, 41(6) msae110, Jun 2024

See more: (Google Scholar (Takahashi)) (Google Scholar (Nozawa))

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