平面虫の不思議な生態
Hello everyone, SCIENSPOT is a podcast that shines a spotlight on the latest scientific
technology from Japan. Your host is REN from SCIEN-TALK. Today's theme is Zero. Can you
imagine a world where gender is zero, no male, no female? In biology, there is a creature
that lives in this gender-zero state, simply cloning itself to survive. That creature is
the planarian. However, under certain conditions, they can leave this zero state and cross
a critical threshold to discover love, or scientifically speaking, sexual reproduction.
Today, I will explain the Japanese research that uncovers the genetic mysteries behind
the point of no return.
So many planarians reproduce asexually. They split their bodies to multiply. In this state,
they have no ovaries and no testes. They literally have zero reproductive organs. But they are
flexible. When the environment changes, they can switch to sexual reproduction, building
these organs from scratch. This process is called sexualization. For about 50 years,
scientists knew that feeding a sexual planarian substance from sexual one could trigger that
switch. But the exact genetic mechanism, what happens inside their cells to turn zero into
one, remained a mystery. A research team led by Professor Kobayashi of Hirosaki University
and Dr. Seki of Keio University tackled this puzzle. They focused on a fascinating concept
called the sexualization inevitability point, or more dramatically, the point of no return.
プラナリアの性転換
Imagine a runway. If a planarian starts the process of becoming sexual but stops halfway,
it can slide back to its original gender zero state. However, once it crosses this
specific point of no return, there is no going back. The body commits to becoming asexual,
even if the external trigger is removed. The team wanted to find the gene responsible for
crossing this line. Using genetic analysis on the planarian, they identified three essential
genes. When they used a technique called RNA interference to block these genes, something
interesting happened. The planarians could form some organs, but they all failed to develop
testis. Without testis, they could not cross the point of no return. This proved that forming
testis is the key to escaping the gender zero world. Furthermore, they found a downstream gene
named Dr. Acidity. This gene creates a protein called inexin which builds tiny tunnels between
cells. These tunnels allow the sperm stem cells to communicate with their support cells. This
connection is vital for building a function testis. So what does this mean? Planarians escape
the gender zero state by activating a sequence of genes that build testis. Once this structure is
established, they cross the threshold and cannot go back. This discovery could help us aim for
zero disease in the future. Planarians are related to parasitic flukes that cause
tropical diseases. These parasites also switch between asexual and sexual stages. If we can block
this genetic switch in parasites, we might prevent them from reproducing and causing harm to humans.
プラナリア研究の重要性
From gender zero to zero diseases, fundamental biology holds amazing potential.
I think this is very interesting research for developing the new treatment for parasites based
on the planarian research. That's all for today's SciencePod. This podcast is broadcast in both
Japanese and English. I'd love for you to listen to the podcast and post your thoughts with
hashtag SciencePod. Thank you for listening and see you next time.
