Molecular Soil Biology 2025, Vol.16, No.6, 287-296 http://bioscipublisher.com/index.php/msb 291 gene is directly regulated by OsARF19 from the auxin pathway, LIC from the BR pathway, and OsZIP26/86 from the ABA pathway (Duan et al., 2023). Under drought and salt stress, crown root development is also controlled by OsWOX11. OsWOX11 works together with the ethylene response factor OsERF3. They repress the expression of OsRR2, a type-A cytokinin response regulator. This weakens cytokinin signaling and shifts the balance toward auxin action. The wox11 mutant has much shorter root hairs. It also shows a weaker response to ethylene-induced crown root initiation when grown in compacted soil (Dabravolski and Isayenkov, 2025). 5 Root Development Genes in Root–Soil Interface Processes 5.1 Genetic regulation of root plasticity under heterogeneous soil environments In this study, researchers worked on both traditional rice and improved rice. They tested 40 different rice genotypes. The main focus was on root traits. These included root dry weight, root length density, and the ratio of lateral roots. The roots were not tested in just one setting. Instead, the plants were grown under different conditions. These conditions included drought stress, re-watering after drought, low phosphorus supply, and different planting methods such as direct sowing and transplanting. The results were quite clear. Rice genotypes with high yield and stable yield usually had better root systems. When the environment became stressful, these plants still kept higher root dry weight and longer roots. In another experiment, researchers studied 274 rice germplasm resources. They measured 35 traits related to root shape and structure. These measurements were done under normal water conditions and also under water shortage. A large number of images were collected during the experiment. Around 45 000 root scanning images and 25 000 images of root base cross-sections were obtained. With these data, the researchers carried out genome-wide association studies (GWAS). Under normal water supply, 104 loci were linked to root traits. Under water stress, 106 loci were found. In addition, 76 loci were related to changes in root traits under different conditions (Kadam et al., 2017). 5.2 Influence of root development genes on root exudation and rhizosphere activity The drought-tolerant rice variety Luodao 998 showed much less suppression of both main roots and lateral roots than the sensitive variety Nipponbare. When drought stress occurred, most organic acids in the root exudates of Luodao 998 increased. At the same time, the content of amino acids generally went down. In contrast, Nipponbare showed only a small increase in organic acids, and some amino acids were still released from the roots. Results from 16S rRNA amplicon sequencing indicated that drought stress did not cause obvious changes in the α-diversity of rhizosphere bacterial communities in either genotype. However, the β-diversity showed clear differences between the two varieties. Under drought conditions, Actinobacteria and several plant growth-promoting bacteria, such as Bacillus, were strongly enriched in the rhizosphere of Luodao 998 (Li et al., 2023). Mantel and Procrustes analyses further showed a strong relationship between the structure of bacterial communities and the metabolic profiles of root exudates. In particular, the abundance of dominant genera, including Streptomyces and Bacillus, was closely linked to the levels of certain organic acids and amino acids. In addition, ABA and JA, which act as signaling hormones in rice root exudates, were able to regulate the abundance of Streptomyces even when plants were not present. 5.3 Implications for nutrient mobilization and root–soil physicochemical interactions When the genes related to root development change, they will directly affect the morphology and secretion mode of the roots. Once the root structure is altered, the environment between the roots and the soil will also change. The way nutrients move at the root-soil interface will change, and the physical and chemical conditions of the soil will also be affected. The ability of rice to absorb nutrients will be affected, and this effect will be more obvious when the soil is poor or under stress. Some genes can control the growth depth and angle of the roots, such as the QTL loci related to deep-rooted traits, which can increase the length of the roots in the deep soil, helping rice better absorb nitrate nitrogen and water from the deep soil. Some other genes will affect the number of crown roots, the density of lateral roots, and the formation of root hairs. These changes are beneficial for rice to absorb nutrients from the surface soil, especially elements such as phosphorus and potassium (Meng et al., 2019). Under different water conditions, some genes are related to the variability of root anatomical structure. These genes participate in the formation of cortical ventilation tissues and the deposition of pericycle sclerification. When the
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