Shohei Takaki, Mizuki Kameda, Haruto Tomizuka

Fungi can sense environmental signals and react accordingly, changing their development, direction of growth, and metabolism. For example, mushroom stems grow upward against gravity. Mushrooms also secrete biochemicals that affect germination, growth, or reproduction of bacteria or plants to protect themselves against them. These mechanisms are called gravitropism and allelopathy, respectively. I studied how Shiitake mushrooms utilize these mechanisms.

 Mushrooms change their growing direction and production of fruiting bodies in response to gravity. However, how other environmental conditions affect mushroom gravitropism has not been fully understood. I investigated the results of our experiments have shown that the angle of mushroom's gravitropism is influenced by various environmental conditions, such as temperatures, pH, fertilizers, and light, and we have focused that the light affects the angle of mushroom's gravitropism strongly. However, what environmental factors play critical roles in mushroom gravitropism is not well understood.

Here we show that the green wavelength has a strong tropism over the gravitropism.

I investigated the relationship between gravitropism and light wavelengths. We grow Shiitake mushrooms (Lentinula edodes) in the laboratory and are exposed to different wavelengths, red (620 ~ 750nm), blue (450 ~ 495nm), and green (495 ~ 570nm). Other conditions were kept the same as the others. The mushrooms subjected to the green light continued bending after they look straight up, while those exposed to red and blue light did not grow well. These results suggest that green wavelength may have some effect to the mushroom.

 Next, we investigated allelopathy in "Hitoyotake Mushroom" (Coprinopsis cinerea). We found that Hitoyotake Mushrooms secret that inhibits plant seeds from growing. Mushrooms were grown in MYG medium. MYG medium consists of “Malt extract”, “Yeast extract”, Glucose, Agar, and Distilled water. Then, we placed either plant seeds (Arabidopsis thaliana) or Escherichia coli into the petri-dish with or without the mushroom and measured the rate of germination and growth. None of the plant seeds germinated in the medium containing the mushroom was grown in the same medium, while 80% of them in the medium without mushroom germinated. Escherichia coli growth rate was almost the same as the medium without mushroom germinated. Although we have not obtained enough number of samples for statistical analyses yet, these results suggest that Hitoyotake Mushroom secreted allelochemicals in the medium.

In summary, I found the light wavelength affects the mushroom. Also, the mushroom itself has effect on other species, like plants. These results help our understanding of fungi biology and may help development of an efficient cultivation method of mushrooms.