Legume Genomics and Genetics 2024, Vol.15, No.5, 244-256 http://cropscipublisher.com/index.php/lgg 248 with improved resilience and yield under adverse environmental conditions (Kudapa et al., 2013; Ramalingam et al., 2015). 5 Case Study: Translational Genomics for Nitrogen Fixation Improvement 5.1 Importance of biological nitrogen fixation in legumes Biological nitrogen fixation (BNF) is a critical process for legumes, allowing them to convert atmospheric nitrogen into a form usable by plants, thus reducing the need for synthetic nitrogen fertilizers. This process not only enhances soil fertility but also contributes to sustainable agricultural practices by reducing greenhouse gas emissions and improving crop resilience (Rodriguez et al., 2020; Karavidas et al., 2022; Ma et al., 2022). Legumes such as common bean and cowpea are particularly valuable in cropping systems due to their ability to fix nitrogen through symbiotic relationships with rhizobia, which significantly boosts soil nitrogen levels and benefits subsequent crops (Kebede, 2021). 5.2 Genomic approaches to enhance symbiotic nitrogen fixation Recent advances in genomics have provided new insights into the genetic mechanisms underlying symbiotic nitrogen fixation (SNF) in legumes. Studies have identified nearly 200 genes involved in SNF, which are crucial for various processes such as nodule formation, microbial infection, and nitrogen assimilation. Genomic tools like transcriptomics, proteomics, and metabolomics have been employed to understand the complex interactions between legumes and rhizobia, leading to the identification of key genes and pathways that can be targeted for improving SNF efficiency (Ramalingam et al., 2015; López et al., 2023). These approaches have been particularly useful in model legumes like Medicago truncatula andLotus japonicus, as well as in crop species such as soybean and common bean (Figure 2) (Roy et al., 2020). Figure 2 Hormonal control of symbiotic nitrogen fixation (Adopted from Roy et al., 2020) Image caption: Ethylene (ET) represses calcium spiking induced upon recognition of a compatible Nod factor (1). Rhizobial infection is countered by the hormones ET, jasmonic acid (JA), and gibberellic acid (GA). By contrast, the hormone cytokinin (CK; whose biosynthesis is mediated by IPT3) and auxin (AUX) signaling (via ARF16a) positively regulate IT development (2 and 3). Multiple hormones control cell divisions at the site of infection that lead to the formation of the nodule primordium (4). As the primordium develops into a mature nodule, hormone requirements differ between indeterminate and determinate nodules (5 and 6). Positive and negative roles are shown in green and magenta, respectively. Medicago gene names are shown unless otherwise indicated (Adopted from Roy et al., 2020) 5.3 Translational research from model systems to cowpea and common bean Translational research aims to apply findings from model systems to improve SNF in crop legumes like cowpea and common bean. For instance, the genetic discoveries in model legumes have paved the way for engineering enhanced SNF capabilities in these crops (Roy et al., 2020). Proteomic and metabolomic studies have revealed
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