Legume Genomics and Genetics 2025, Vol.16, No.5, 204-214 http://cropscipublisher.com/index.php/lgg 210 more, and even the overall growth of roots has improved. Behind these phenomena, almost all of them are inseparable from the "behind-the-scenes actions" of bloating proteins in cell wall modification (Dabravolski and Isayenkov, 2025). Judging from these results, whether in normal development or under adverse conditions, blotin seems to be helping cells "unbind", allowing plants to cope with the environment more calmly. 6.3 Omics approaches (transcriptomics, proteomics) identifying candidate expansins in stress and development Not every expansion protein can be immediately identified for its function, especially during complex stress responses or developmental processes. At this point, omics technology comes into play. Like in wild soybeans, transcriptome analysis revealed that some expansins were specifically induced to be expressed under conditions such as salt, drought, and cold, and this expression often carried organ specificity. Promoter analysis further tells us that their regulation is not only dependent on environmental stimuli, but also involves developmental processes, hormone signals, and even adverse cis-regulatory elements (Chen et al., 2020). Proteomics and co-expression networks have not been idle either. Research results indicate that a batch of candidate genes for bulking proteins may be involved in processes such as cell wall remodeling, antioxidant defense, and osmotic regulation. Although these data cannot be used to draw a direct conclusion, they at least provide a very clear clue-we can understand the position of these genes in plant adaptability from a broader perspective, especially in leguminous crops that are particularly sensitive to environmental responses. 7 Case Study: Expansin Gene Functions in Soybean (Glycine max) 7.1 Genome-wide identification and classification of expansin genes in soybean If asked which crop has the "most complete" family of expansive proteins, soybeans must be on the list. So far, 75 expin genes have been identified and are distributed in four subfamilies: EXPA, EXPB, EXLA and EXLB. EXPA has the largest number of members, accounting for approximately two-thirds. In contrast, EXLA is relatively "less popular" and has the fewest quantity. These genes are not only numerous but also structurally interesting. Genes within the same subfamily are often highly similar in intron and exon structures and share some conserved motifs, which indicates that they are very likely to have evolved from a common "ancestral module". Of course, the formation of such diversity does not come out of thin air-fragment repetition and serial replication events are all driving the expansion and functional differentiation of this family. 7.2 Expression profiling under drought and nodulation stages reveals functional clusters The presence of expansive proteins in soybeans is not even, especially in areas such as roots and root nodules, where they are often much more active. The analysis of the expression profile reveals some patterns, but also brings out a lot of complexity. Genes like GsEXPB1 and GsEXLB14 are "resident" genes in the roots, and they will be significantly upregulated especially when encountering drought or salt stress. GmEXPB2 and GmINS1, on the other hand, are more likely to be expressed when root nodules form or when plants are deficient in phosphorus. Their changes are even associated with the size of root nodules and the enhancement of nitrogen fixation capacity. Not all expansins are activated under adverse conditions. Some only work at specific times and in specific areas. For instance, during the tumor formation stage, some genes are activated particularly early, while others "make a grand entrance". Transcriptome data further support this point-their expression is influenced by both abiotic stress and developmental stage (Li et al., 2015; Yang et al., 2021). 7.3 Transgenic approaches demonstrate roles in root elongation and abiotic stress tolerance The most direct way to figure out exactly what a certain expansin is "responsible for" is through transgenic experiments. Many studies nowadays are conducted in this way. Both transgenic experiments on the hairs of soybean roots and the entire plant have found that after overexpressing genes such as GsEXPB1, GsEXLB14, GmEXPB2 or GmEXPA7, the number, length and biomass of roots all increased, and the plant's tolerance to stress such as salt, drought and low phosphorus also improved accordingly. However, this matter is not one-sided. If we change our approach and deal with it by interfering with or inhibiting these genes, the results will soon become apparent: the roots won't grow and there will be problems with the formation of nodules. For instance, GsEXPB1
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