Legume Genomics and Genetics 2024, Vol.15, No.4, 163-175 http://cropscipublisher.com/index.php/lgg 169 nodulation, and nitrogenase activity. This is achieved through the upregulation of symbiosis-related genes in both the rhizobium and soybean, suggesting that H2S enhances the nitrogen fixation ability of the symbiotic system (Fan et al., 2022). Iron transport across the symbiosome membrane is another critical factor for effective nitrogen fixation. The iron transporter GmVTL1a, localized on the symbiosome membrane, is responsible for supplying iron to the bacteroids, which is essential for the activity of the nitrogenase enzyme. Mutations in GmVTL1a that impair iron transport result in reduced nitrogen fixation, underscoring the importance of iron homeostasis in the symbiotic relationship (Bender et al., 2022). Figure 3 GmYSL7 is expressed in infected cells of soybean root nodules (Adopted from Gavrin et al., 2021) Image caption: A, Transcript level of GmYSL7 in tissue samples from different organs. DNR, denodulated roots; nd, not detected. B, Transcript level of GmYSL7 during nodule development. 6R, roots 6 d after inoculation (DAI); 10RN, roots and nodules 10 DAI; 13N-26N, nodules the indicated DAI. Data shown are from three independent time courses. Error bars are SE (n = 3). Nitrogenase activity was first detected at 18 DAI. The relative expression was quantified by RT-qPCR and normalized to a soybean ubiquitin gene (GmUBI3, Glyma20g27950.1). C, Transgenic root expressing pYSL7: GFP-GUS. GUS staining was not detectable in the very early stages of nodule development. Arrowhead indicates a nodule initiation. D, Transgenic pYSL7: GFP-GUS 10-d-old nodule primordia. IR, infected region. E, Transgenic pYSL7:GFP-GUS mature nodule. GUS staining is restricted to infected cells. OC, outer cortex. F, Magnification of E. Scale bars, 150 μm (Adopted from Gavrin et al., 2021) 5.3 Genetic basis of soybean’s nodulation efficiency The genetic basis of nodulation efficiency in soybean (Glycine max) is a complex interplay of various genes and molecular pathways that regulate the formation and function of nodules, which are essential for symbiotic nitrogen fixation. This section delves into the key genetic components and mechanisms that contribute to the nodulation efficiency in soybean. GmACP plays a crucial role in nodulation by participating in fatty acid biosynthesis. Silencing of GmACP results in a significant reduction in nodule numbers, indicating its importance in the nodulation process (Li et al., 2022).
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