Rice Genomics and Genetics 2025, Vol.16, No.3, 150-158 http://cropscipublisher.com/index.php/rgg 153 Nutrient availability, particularly nitrogen and phosphorus, plays a crucial role in modulating RSA. Efficient nutrient uptake is often linked to specific root traits such as root length, density, and branching patterns. For example, the presence of certain quantitative trait loci (QTLs) and transporters for nutrients has been identified as critical for developing an ideal RSA that enhances nutrient uptake efficiency (Liu et al., 2021). Marker-assisted selection and QTL cloning are being utilized to exploit these genetic variations, aiming to optimize RSA for better nutrient acquisition (Dorlodot et al., 2007). 3.2 Water availability Drought stress triggers significant changes in RSA to enhance water uptake. Rice plants with a deep and branched root system are better equipped to access water from deeper soil layers. Studies have shown that drought-tolerant genotypes like Azucena enhance root growth and exploration under water stress, whereas drought-susceptible genotypes like IR64 may rely more on cell insulation and antioxidant systems to withstand stress (Teramoto et al., 2020; Ranjan et al., 2022). The identification of QTLs and genes associated with RSA under drought conditions has been pivotal in breeding drought-tolerant rice varieties (Maqbool et al., 2022). Waterlogging conditions also necessitate specific RSA adaptations. Rice plants often develop aerenchyma, which are air-filled spaces in the root cortex, to facilitate oxygen transport to submerged roots. This adaptation helps in maintaining root function and overall plant health under hypoxic conditions. The genetic basis for these adaptations includes various QTLs and genes that regulate root growth and development in response to waterlogging (Rogers and Benfey, 2015; Panda et al., 2021). 3.3 Interaction with soil microbiota Mycorrhizal fungi form symbiotic relationships with rice roots, significantly influencing RSA. These fungi enhance nutrient uptake, particularly phosphorus, by extending the root's absorptive surface area. The interaction between mycorrhizal fungi and rice roots can lead to changes in root branching and length, optimizing the plant’s ability to access soil nutrients (Rogers and Benfey, 2015). This symbiosis is crucial for improving nutrient use efficiency and overall plant health. The rhizosphere, the soil region influenced by root exudates, hosts a diverse microbial community that interacts with rice roots. These microbial interactions can modulate RSA by influencing root growth patterns and nutrient uptake. For instance, certain beneficial microbes can promote root branching and elongation, enhancing the plant's ability to acquire nutrients and water (Rogers and Benfey 2015; Rogers et al., 2016). Understanding the dynamics of the rhizosphere microbial community and its impact on RSA is essential for developing sustainable agricultural practices. 4 Case Study 4.1 Criteria for selecting the case study The selection of the case study focused on identifying a genetic pathway with significant influence on root system architecture (RSA) in rice, particularly under environmental stress conditions. The DRO1 gene was chosen due to its well-documented role in enhancing drought tolerance by promoting deeper root growth, which is crucial for water uptake during periods of water scarcity. This gene has been extensively studied and validated in various research contexts, making it an ideal candidate for a detailed analysis (Panda et al., 2021). 4.2 Detailed analysis of a specific genetic pathway influencing RSA The DRO1 (Deeper Rooting 1) gene is a key genetic determinant of root depth in rice. It has been shown to significantly influence the angle of root growth, promoting deeper rooting systems that enhance the plant’s ability to access water from deeper soil layers. This trait is particularly beneficial under drought conditions, where surface water is limited (Daryani et al., 2021). The DRO1 gene functions by modulating the gravitropic response of roots, thereby altering their growth direction and enabling the plant to maintain water uptake during periods of drought (Figure 2) (Panda et al., 2021).
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