Behind the scenes of the birth of life: The crossroads of generality and diversity

Department of Biology — Yoshida Laboratory

Associate Professor Manabu Yoshida
University of Tokyo Misaki Marine Biological Station
Graduate School of Sciences

Professor Yoshida graduated from the zoology course in the University of Tokyo’s Department of Biology in 1990. In 1995 he obtained his Ph.D. in Science after completion of the zoology program in the Graduate School of Sciences. He then became a RIKEN Special Postdoctoral fellow, and in 1998 took a position as an assistant professor at the University of Tokyo Misaki Marine Biological Station. After serving in 2001 as a visiting researcher at Statione Zoologica Anton Dohrn in Naples, Italy, he became a researcher at the Japan Science and Technology Agency’s Calcium Oscillation Project. He then became an instructor at the University of Tokyo Misaki Marine Biological Station, and took up his current position in 2009.

Living organisms occupy the niche between generality and diversity. There are an estimated ten million forms of life on our planet, each one adapted to its particular environment through survival strategies reflected in the organisms’ diverse forms.

Yet there are many similarities among the mechanisms and structures utilized by this wide variety of organisms. All living things are composed of cells, and those cells are largely the same, being composed of water, proteins, and nucleic acids. Also similar among all living things is that they obtain energy to perform life activities through techniques such as photosynthesis or respiration, and each has a method for self-replication of genetic information to pass on to the next generation.

All organisms that engage in sexual reproduction create new life through a fertilization process that relies on the joining of a male sperm and a female egg. However in the midst of this universal process there are species-specific characteristics, says Associate Professor Manabu Yoshida, whose research focuses on fertilization. From the moment that a single new life is created, all organisms display a combination of generality and diversity.

From research related to gene functions we have learned that there are some genes that will function without problems even after being transferred into a new species. This is a demonstration of the similarities between different species. In most cases, however, fertilization cannot occur through the meeting of egg and sperm from different species, even if they are closely related. “I want to know more about the protective mechanisms that maintain the uniqueness of species by blocking cross-fertilization,” Professor Yoshida says. “By learning more about fertilization, we can close in on many mysteries in biology.”

There are multiple facets to fertilization. “We tend to think of sperm as restlessly moving little things, but they move about only after being released from the male body,” says Professor Yoshida. “Also, a remarkable feature in organisms that use external fertilization is that sperm can find their way thanks to chemoattractants released by the eggs. In mammalian semen, there are substances that prevent fertilization. Those substances are broken down in the female’s uterus, allowing fertilization to occur.”

There is a complex mechanism and delicate timing behind the meeting of sperm and egg for fertilization. There are many hurdles that must be crossed for new life to be created, and many of these remain only poorly understood.

Although his research also includes fertilization in mice, Professor Yoshida’s laboratory is part of the Marine Biological Station in the Graduate School of Science. Established in 1886, it is one of the oldest marine laboratories in the world, and is located at Misaki, at the southwest tip of the Miura Peninsula, which is home to a bountiful array of biota. There, Professor Yoshida studies the fertilization of marine invertebrates such as tunicates.

Students perform research following individual themes, but every other week they meet for team discussions. “But they’re more like family gatherings,” says Chihiro Ono (D2). “Even the professor’s wife joins in.” Professor Yoshida also sometimes hosts parties at his home, at which he shows off his skill as a chef.

The laboratory is host to researchers from around the world—including Spain, Czech, Hungary, and Australia—who stay for up to half a year to explore the area’s rich biota, or who participate as part of the international network of marine laboratories. Lab members are able to interact with these international visitors through welcome parties held to greet them, or during their stay at the lodging provided at the lab facilities. As Takuya Yamamoto (M1) says, “You definitely feel like you’re connected to the rest of the world here.” Naoya Araki (D3) agrees: “We get the opportunity to travel overseas at least once a year, for joint research projects, conferences, and the like.”

Our oceans truly connect the world, both physically and through the researchers who study it.

Eggs from the tunicate Ciona intestinalis release the chemoattractant steroid SAAF to guide sperm cells. When a sperm heads in a direction away from the egg (a direction in which the concentration of SAAF becomes lower), levels of Ca2+ transiently rise in its flagellum, causing it to change direction until it is once again oriented toward the egg.

Student evaluations
 “It’s amazing how much Professor Yoshida knows—he’s like a walking Wikipedia.” (Naoya Araki, D3)
“He has friends all over the world.” (Chihiro Ono, D2)
“The Italian food he makes at his parties is amazing.” (Takuya Yamamoto, M1)

― Office of Communication ―