Rhythmic control by plants is essential for symbiosis with bacteria that nourish plants

July 19, 2024

Legume’s periodic rhythm regulates its symbiosis with root nodule bacteria

Legumes can grow under nitrogen-limiting soil conditions by symbiosis with root nodule bacteria. This is because the bacteria can convert aerial nitrogen into ammonia (nitrogen fixation ability), enabling legumes to use nitrogen in the air. Legumes host these beneficial bacteria in lumpy root nodules. However, too many nodules indiscriminately formed along roots could disturb the essential root functions, such as delivering water and nutrients from soil to leaves and stalks. Therefore, host legumes must regulate the root nodule formation so that the nodules are not distributed too densely by rhizobia infection. However, the mechanism of this regulation has yet to be understood.

This study used the model legume Lotus japonicus to demonstrate that the host response to rhizobia in the root is accompanied by periodic gene expression in steady rhythm. It also found that this periodic expression defines the size of the root region where rhizobia can infect, regulating the distribution of root nodules. In addition, the research revealed that a plant hormone, cytokinin, is required to maintain the rhythm of gene expression.

Further research is expected to elucidate the regulation mechanism of root nodule symbiosis and further understand the space control mechanism of organ development with periodic responses through plant hormones.

Original article

Science doi: 10.1126/science.adk5589

T. Soyano, A. Akamatsu, N. Takeda, M. K. Watahiki, T. Goh, N. Okuma, N. Suganuma, M. Kojima, Y. Takebayashi, H. Sakakibara, K. Nakajima, M. Kawaguchi,

"Periodic cytokinin responses in Lotus japonicus rhizobium infection and nodule development".

Contact

Hitoshi Sakakibara; Senior Visiting Scientist
Mikiko Kojima; Expert Technician
Yumiko Takebayashi; Technical Staff I
Mass Spectrometry and Microscopy Unit