Legume Genomics and Genetics 2025, Vol.16, No.3, 143-152 http://cropscipublisher.com/index.php/lgg 145 3 Root Development in Legumes: A Biological Framework 3.1 Root architecture and developmental zones The root system of legumes consists of three main parts which include the primary root and lateral roots and the specialized nodules. The primary root contains three main developmental areas which include the root apical meristem for cell division and the elongation zone for cell growth and the differentiation zone for cell maturation and specialization. The formation of lateral roots happens after embryonic development to create a flexible root system which helps plants adapt to their environment (Bensmihen, 2015). The root system of plants shows strong reactions to environmental factors including nutrient availability and stress conditions like phosphorus deficiency and drought (Ye et al., 2018; Chen et al., 2023). Figure 1 Strategies for improving P acquisition efficiency through gene regulation in legumes. In legumes, P acquisition efficiency can be achieved by remodeling of root morphology and architecture, inducing high-affinity Pi transporters, increasing root exudates to facilitating P mobilization, and activating Pi signaling network. A variety of Pi starvation-induced (PSI) genes have been implicated in improving P acquisition efficiency in legumes. These are related to root growth, Pi uptake, insoluble P mobilization and Pi signaling network (Adopted from Chen et al., 2023) 3.2 Genetic regulation of root cell fate and differentiation Multiple genetic systems consisting of transcription factors and microRNAs and hormonal signaling pathways work together to control the development of legume roots. The SHORTROOT–SCARECROW (SHR–SCR) module functions as a key regulator that determines cortical cell fate while being vital for nodule organogenesis (Dong et al., 2020). The NODULE INCEPTION (NIN) transcription factor controls both nodule and lateral root development through its regulation of downstream targets that include ASL18/LBD16a and NF-Y subunits (Soyano et al. 2019; Suzaki, 2023). The microRNAs miR166 and miR2111 control transcription factor expression and systemic signaling pathways which affect both root development and nodule formation (Gautrat et al. 2020; Boualem et al., 2008). Plant hormones including auxin and cytokinin and abscisic acid and strigolactones function as either opposing or cooperative factors that regulate the development of lateral roots and nodules (Bensmihen, 2015; Gauthier-Coles et al., 2019; Goto et al., 2022).
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