National Taiwan University research team discovered IDD7, a key regulator of symbiosis between rice and fungi

The roots of rice also have "fungi good friends". The rice provides the carbon source needed for fungi to grow, and the fungi help obtain important nutrients such as phosphorus from the soil. The team of Yang Shuyi, associate professor at the Institute of Plant Science at National Taiwan University, spent nearly eight years researching and found the important "switch" IDD7 that maintains this mutually beneficial relationship. When rice lacks IDD7, the degree of symbiosis of fungi in the roots is significantly reduced, and the "arbuscular hyphae" responsible for exchanging nutrients cannot develop normally. The research has revealed the key to improving the nutrient efficiency of rice, and has been published in the international journal "Nature Communications."

The symbiosis between plants and "arbuscular mycorrhizal fungi" is a very common mutually beneficial relationship between plants and microorganisms in nature. After the fungus enters the roots of the plant, it will form "arbuscular hyphae" that are highly branched and look like twigs, which act like a "nutrient exchange station" for both parties: the plant provides the carbon source needed by the fungus, and the fungus helps the plant obtain nutrients such as phosphorus in the soil.

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The research team discovered that one of the keys is a transcription factor called IDD7. When rice root cells contain arbuscular hyphae, IDD7 will be expressed in large quantities; in rice lacking IDD7, not only the degree of fungal symbiosis is reduced, but also the development of arbuscular hyphae is affected, and many genes related to nutrient transport, fatty acid synthesis and symbiosis cannot be started normally.

The study further found that IDD7 cooperates with two other important regulatory proteins. SLR1 is involved in the signaling of the plant hormone gibexin, and PHR2 regulates the plant's response to phosphorus nutrition. The three work together to more effectively activate multiple key genes required for mycorrhizal symbiosis. IDD7 itself can also regulate the expression of PHR2.

In other words, IDD7 is like a "transportation hub" that connects different information such as rice growth, phosphorus nutrition and fungal symbiosis, and then coordinates the operation of related genes to allow rice and fungi to exchange nutrients smoothly.

The research team said that arbuscular mycorrhizal fungi can help crops obtain soil nutrients and may also improve plants' ability to face environmental stress. Clarifying the molecular mechanisms controlling mycorrhizal symbiosis in rice is expected to serve as a scientific basis for improving crop nutrient use efficiency and stress adaptability in the future. The next step will be to explore how IDD7 cooperates with other regulatory proteins and chromatin regulatory mechanisms, and whether it is involved in improving rice stress tolerance.

The research was chaired by Yang Shuyi, with Chen Peirong, Du Qicong, Zhang Yuting, He Minzhi, Guo Wanni, Guo Zhenglin, Zhang Kaijie and Lin Yizeng as co-first authors. Shi Xuanzhi and Professor Zheng Yisheng of the Department of Life Sciences of National Taiwan University also participated in the research. It lasted nearly 8 years and was completed by multiple graduate students.