Plants dramatically change their root structure in response to nitrogen concentration in the soil. For example, in nitrogen-rich environments, plants determine that "nitrogen is sufficiently present" and suppress root growth to avoid unnecessary energy consumption. However, the detailed mechanism behind this had remained unknown until now.
A research group led by Lecturer Kensuke Kusumi, Graduate Student Kazuhiro Ito (at the time of the research), and Graduate Student Tomoya Sonoda from the Faculty of Science at Kyushu University, in collaboration with Professor Hidehiro Fukaki from the Graduate School of Science at Kobe University, Professor Kousuke Hanada from the Graduate School of Computer Science and Systems Engineering at Kyushu Institute of Technology, Professor Takamasa Suzuki from the College of Bioscience and Biotechnology at Chubu University, and Professor Takumi Higaki from the Faculty of Advanced Science and Technology at Kumamoto University, used the model plant Arabidopsis thaliana to elucidate clarify the peptide LOHN1 and the previously unknown mechanism of high-nitrogen information signal transduction involving the peptide LOHN1, which functions to suppress root growth in high-nitrogen environments. Their findings were published in the online edition of Current Biology.
Under nitrogen deficient conditions, Arabidopsis plants promote root development in response to N concentration to explore the surrounding soil. In contrast, under high-N conditions, lateral root (LR) formation is repressed; however, LOHN1 knockout (LOHN1-KO) plants do not exhibit LR repression.
Provided by Kyushu University
Analysis of plants with modified LOHN1 gene expression revealed that when plants are placed in a high-nitrogen environment, nitrogen metabolism is promoted. As a result, glutamic acid, a type of amino acid, is transported from the shoot through the phloem to the root tip, where it induces LOHN1 gene expression. Furthermore, it was found that the expressed LOHN1 peptide moves from phloem cells to the outer layer of the root, where it controls and suppresses lateral root density.
The findings obtained in this study can be applied to many other plant species, and it is expected that this will enable improved nitrogen use efficiency in crops and the artificial control of root growth in response to fertilization.
Kusumi commented: "This research has revealed the mechanism behind the long-known phenomenon of 'suppression of root formation in high-nitrogen environments.' Going forward, we aim to elucidate the regulatory mechanism of lateral root density through auxin transport, in which LOHN1 is involved."
Journal Information
Publication: Current Biology
Title: Arabidopsis LOHN1 peptide modulates lateral root spacing under the control of systemic nitrogen-satiety signaling
DOI: 10.1016/j.cub.2025.09.060
This article has been translated by JST with permission from The Science News Ltd. (https://sci-news.co.jp/). Unauthorized reproduction of the article and photographs is prohibited.