Silicon (Si) is one of the most abundant elements on Earth, found in large quantities in soil. While Si is not essential for land plants, many plants, such as rice and grasses, have used Si to develop powerful defense mechanisms against various environmental stresses. Si accumulates in plant leaves and aerial organs as amorphous silica (SiO2), which offers protection against pathogens, herbivores, and environmental challenges like drought. Understanding the processes through which plants manage this beneficial element could enhance crop resilience and productivity, especially in the face of climate change.
In a breakthrough study, a team of researchers led by Dr. Naoki Yamaji, from the Institute of Plant Science and Resources, Okayama University, Japan, has uncovered a key signaling protein, Shoot-Silicon-Signal (SSS), that regulates Si uptake, distribution, and accumulation in rice and other grasses. Their research focused on Oryza sativa, a rice variety known for its high Si accumulation, and relies heavily on Si for healthy growth and productivity. The team consisted of Dr. Namiki Mitani-Ueno and Dr. Jian Feng Ma from the Institute of Plant Science and Resources, Okayama University, Japan. This study, published online in Volume 15 of Nature Communications on December 27, 2024, sheds light on the evolution of SSS in rice crops as a defense mechanism. Dr. Yamaji says, "We have been studying Si nutrition in plants and have identified several Si transporters for Si uptake, distribution, and accumulation. Now, we have researched the signaling protein."
SSS is an unusually exceptional homolog of florigen, a hormone that regulates flowering in plants. While florigen plays a role in plant development, SSS plays a crucial role in regulating Si. The researchers discovered that when Si is available, the level of SSS protein in the plant drops, signaling the plant to adjust its Si intake accordingly. They used wild-type (naturally occurring) rice variety, modified (mutated) cell lines of the SSS gene, and a transgenic cell line of rice containing genes of SSS protein and green fluorescent protein.
The team utilized multiple biotechnological advancements to create mutated and transgenic cell lines. They then performed various analyzes on the expression of the SSS gene and the presence of SSS protein in various parts of the plant. In rice plants with mutated SSS gene, Si uptake from the roots was significantly reduced, causing a drop in the grain yield. This highlights the important role of SSS in regulating Si absorption and accumulation. Also, the scientists found that in leaves, the SSS gene is expressed in the phloem—a tissue that helps in the transportation of food in plants.
The findings have exciting implications for agriculture. By using SSS protein as a marker, scientists can better estimate the Si requirements of a plant and consequently optimize Si fertilization. This could result in more resilient crops that are better equipped to cope with environmental stresses, ultimately boosting agricultural productivity and sustainability. Dr. Yamaji emphasizes, "Si accumulation in plants alleviates various biotic and abiotic stresses. Therefore, optimization of Si makes more stress-tolerant crops. It contributes to the productivity and sustainability of agriculture".
Si accumulation and regulation also help the plant to adapt to the environmental conditions. Though Si is not considered an essential element for plant growth, the study proves its indispensable role as an adaptive element. Dr. Yamaji adds about the potential implications of the study, "This discovery opens up new possibilities for improving Si management in crops, particularly in regions where Si availability in soil is lowered by cultivation. By better understanding how plants regulate Si, we can design more efficient fertilization strategies and enhance crop resilience globally."
As climate change continues to threaten agricultural stability, improving Si management could become a key strategy for ensuring a more resilient food supply. Dr. Yamaji concludes, "Si is not just an element that plants accumulate, it's an adaptive tool that helps them thrive and survive. By harnessing the power of Si, we can help ensure a more sustainable and productive agricultural future."
About Okayama University, Japan
As one of the leading universities in Japan, Okayama University aims to create and establish a new paradigm for the sustainable development of the world. Okayama University offers a wide range of academic fields, which become the basis of the integrated graduate schools. This not only allows us to conduct the most advanced and up-to-date research but also provides an enriching educational experience.
Website: https://www.okayama-u.ac.jp/index_e.html
About Associate Professor Naoki Yamaji from Okayama University, Japan
Dr. Naoki Yamaji is an Associate Professor at the Institute of Plant Science and Resources, Okayama University, Japan. He has published over 200 research papers, 40,000 reads and more than 25,000 citations. He was honored with the Young Scientists' Prize in 2017, a prestigious national recognition. His research primarily focuses on plant physiology, rice, plant biotechnology, plant environmental stress physiology, and plant molecular biology. Additionally, Dr. Yamaji's work delves into plant molecular biology, aiming to enhance crop resilience and productivity through a deeper understanding of plant responses to environmental challenges.
