2025-03-21 マックス・プランク研究所
The roots of Lotus japonicus plants form nodules (visible as spherical structures) that host rhizobium bacteria, enabling nitrogen fixation.
© Defeng Shen
マックス・プランク分子植物生理学研究所の研究者らは、植物の根の「カスパリー線(Casparian strip)」が、マメ科植物における窒素固定と根粒形成に重要な役割を果たしていることを明らかにしました。カスパリー線は、根の内皮にある疎水性の細胞壁構造で、物質の選択的通過を制御します。
◆研究では、モデル植物Medicago truncatulaの遺伝子改変によってカスパリー線の形成を妨げると、根粒数が減少し、リゾビウム細菌の感染効率も低下することが分かりました。これは、適切なカスパリー線の形成が、根の中の化学環境を整え、共生に必要なシグナル伝達や栄養素の流れを調整しているためと考えられます。この知見は、持続可能な農業に向けて、窒素肥料の使用を減らす新たなアプローチに貢献する可能性があります。
<関連情報>
- https://www.mpg.de/24354080/the-role-of-the-casparian-strip-in-nitrogen-fixation
- https://www.science.org/doi/10.1126/science.ado8680
アポプラストバリアはミヤコグサにおける根粒形成と窒素固定に必須である Apoplastic barriers are essential for nodule formation and nitrogen fixation in Lotus japonicus
Defeng Shen, Nikola Micic, Rafael E. Venado, Nanna Bjarnholt, […], and Tonni Grube Andersen
Science Published:20 Mar 2025
DOI:https://doi.org/10.1126/science.ado8680
Editor’s summary
Vascular plants regulate the flow of water and nutrients through their roots by creating a barrier in their extracellular space called the Casparian strip. Shen et al. identified genes involved in Casparian strip formation in Lotus japonicus, a legume that forms symbiotic relationships with nitrogen-fixing bacteria. Furthermore, the authors established that mutants lacking a Casparian strip were less able to form nitrogen-fixing root nodules, implying a connection between these processes. The presence of the Casparian strip also affected expression of the root-shoot signaling peptides that regulate nodulation. This work expands the role of the Casparian strip and links it to the spatial regulation of nodulation in plant roots. —Madeleine Seale
Abstract
Establishment of the apoplastic root barrier known as the Casparian strip occurs early in root development. In legumes, this area overlaps with nitrogen-fixing nodule formation, which raises the possibility that nodulation and barrier formation are connected. Nodules also contain Casparian strips, yet, in this case, their role is unknown. We established mutants with defective barriers in Lotus japonicus. This revealed that effective apoplastic blockage in the endodermis is important for root-to-shoot signals underlying nodulation. Our findings further revealed that in nodules, the genetic machinery for Casparian strip formation is shared with roots. Apoplastic blockage controls the metabolic source-sink status required for nitrogen fixation. This identifies Casparian strips as a model system to study spatially constrained symbiotic plant-microbe relationships.
