Legume Genomics and Genetics 2024, Vol.15, No.4, 163-175 http://cropscipublisher.com/index.php/lgg 163 Systematic Review Open Access Molecular Mechanisms of Nitrogen-Fixing Symbiosis in Fabaceae Weiguo Lu, Qishan Chen Modern Agricultural Research Center, Cuixi Academy of Biotechnology, Zhuji, 311800, Zhejiang, China Corresponding email: qishan.chen@cuixi.org Legume Genomics and Genetics, 2024 Vol.15, No.4 doi: 10.5376/lgg.2024.15.0017 Received: 04 Jul., 2024 Accepted: 05 Aug., 2024 Published: 16 Aug., 2024 Copyright © 2024 Lu and Chen, This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Lu W.G., and Chen Q.S., 2024, Molecular mechanisms of nitrogen-fixing symbiosis in Fabaceae, Legume Genomics and Genetics, 15(4): 163-175 (doi: 10.5376/lgg.2024.15.0017) Abstract Nitrogen-fixing symbiosis in Fabaceae, facilitated by the interaction between legumes and rhizobia bacteria, plays a crucial role in sustainable agriculture by enhancing soil fertility and reducing the need for synthetic fertilizers. This study aims to provide a comprehensive overview of the molecular mechanisms underlying this symbiotic relationship. The study explores the genetic, biochemical, and physiological processes involved in the establishment and maintenance of nitrogen-fixing nodules. Key signaling pathways, gene expression profiles, and regulatory networks are discussed, highlighting the roles of nodulation factors, receptor kinases, and transcription factors. Furthermore, the study examines the latest advancements in molecular techniques and their applications in enhancing symbiotic efficiency and nitrogen fixation. Understanding these mechanisms is vital for developing strategies to improve crop productivity and environmental sustainability. Keywords Nitrogen-fixing symbiosis; Fabaceae; Rhizobia; Nodulation factors; Gene expression profiles 1 Introduction Nitrogen is a critical nutrient for plant growth, yet it is often a limiting factor in many ecosystems. Biological nitrogen fixation (BNF) is a process that converts atmospheric nitrogen (N2) into ammonia, a form that plants can readily absorb and utilize. This process is primarily facilitated by nitrogenase enzymes found in certain bacteria, which can either live freely in the soil or form symbiotic relationships with plants (Dixon and Kahn, 2004). Among the plant families, Fabaceae (legumes) are particularly notable for their ability to engage in symbiotic nitrogen fixation with rhizobia bacteria. This symbiosis not only enhances the nitrogen content in the soil, promoting plant growth and soil fertility, but also reduces the need for synthetic nitrogen fertilizers, thereby contributing to sustainable agricultural practices (Liu et al., 2018; Aasfar et al., 2020). The symbiotic relationship between legumes and rhizobia is a complex and highly regulated process. It begins with the infection of legume roots by rhizobia, leading to the formation of specialized structures called root nodules. Within these nodules, rhizobia differentiate into bacteroids, the form in which they fix nitrogen (Lodwig et al., 2003; Liu et al., 2018). The nitrogenase enzyme in bacteroids catalyzes the reduction of atmospheric nitrogen to ammonia, which is then assimilated by the plant. This process is energy-intensive and requires a continuous supply of carbon compounds from the plant to the bacteroids (Bellenger et al., 2020; Aasfar et al., 2021). Additionally, the symbiotic nitrogen fixation process is tightly regulated by both the host plant and the bacteria, involving intricate genetic and signaling interactions to ensure efficiency and responsiveness to environmental conditions (Dixon and Kahn, 2004; Berger et al., 2020). This study aims to elucidate the molecular mechanisms underlying nitrogen-fixing symbiosis in Fabaceae. The specific objectives are to examine the genetic and biochemical pathways involved in the formation and functioning of root nodules, investigate the regulatory networks that control nitrogen fixation and their responses to environmental cues, and explore the evolutionary aspects of nitrogen-fixing symbiosis in Fabaceae, including the phylogenetic relationships and divergence times of key species. Additionally, the study will assess the potential applications of this knowledge in improving agricultural practices and promoting sustainable crop production. By synthesizing current research findings, this study seeks to provide a comprehensive understanding
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