Legume Genomics and Genetics 2025, Vol.16, No.2, 54-62 http://cropscipublisher.com/index.php/lgg 56 obvious expansion is mostly related to plant-pathogen interactions, isoflavone synthesis, terpene metabolism, unsaturated fatty acid pathways, etc., all of which are related to plants' responses to the environment and the diversity of their nutritional composition. Behind such expansions are often serial repetitions or fragment repetitions at work. However, even if duplication occurs, the vast majority of gene pairs still retain their original functions because they are all under the pressure of purification selection. In contrast, although the number of shrinking families is also considerable, they are not as prominent in terms of functional enrichment. 3.2 Differences in stress-responsive gene families When it comes to responding to adversity, some genetic families of mung beans are actually quite "versatile". The OSCA family is an example. There are a total of 13 members, and many of them will be activated under drought or salt stress (Yin et al., 2021). However, although these members are repetitive, their expressive behaviors are different from each other. Clearly, they are no longer cast from the same mold - functional differences have already been established. Looking at the BBX family, the number is slightly smaller, with 23 members. The expansion mainly relies on fragment repetition. This type of gene is highly sensitive when treated with ABA, PEG or NaCl, especially VrBBX5, VrBBX10 and VrBBX12. They can often be seen in the expression profile and seem to be particularly active under stress conditions (Yin et al., 2024). In addition, the NAC family is even larger, with as many as 81 members. Its role can be found in almost all kinds of coercive scenarios. According to the hint of the co-expression network, they may not be the scraps but the "backbone" in the stress resistance strategy of mung beans. 3.3 Evolutionary features of genes related to yield and quality The evolution of gene families is not only related to resistance, but also to yield and quality. During the domestication process of mung beans, some genes related to flowering time or color have undergone PAV variations, and these variations are actually conducive to early flowering and wider adaptation in different environments (Liu et al., 2022). Looking at the genes involved in starch synthesis, sucrose metabolism, amino acids and secondary metabolism, many are concentrated in the specific or expanded families of mung beans. That is to say, these functions may be related to its characteristics of high protein and high nutritional density (Liu et al., 2022). In terms of some more "practical" traits, such as pod cracking, the PDH1 gene has been explicitly named as one of the key domestication sites regulating this trait (Li et al., 2024), because it is directly related to whether the pods can be harvested smoothly. 4 Genetic Diversity and Population Structure 4.1 Distribution patterns of SNPs and InDels in wild and cultivated mung bean In mung beans, the distribution of genetic variations is not even and is not as simple as imagined. Resequencing data revealed that there were over one million proprietary SNPS in the cultivated population, while the number of structural variations (SVS) in the wild population was significantly higher (Jia et al., 2024). It is worth noting, however, that most of the variations are low-frequency variations (sub-allele frequencies <0.05), among which deletion type SV is the most common. Across the entire genome, the distribution of SNPS and SVS is highly consistent, but there are also some regions that are "abnormally active", with a particularly large accumulation of variations. These hotspots may reflect traces of past domestication or strong selection. Although technological means are becoming increasingly advanced, such as high-quality genome assembly which enables us to observe millions of SNPS and tens of thousands of Indels, it is still not easy to explain the biological significance behind these variations. 4.2 Population structure and phylogenetic analysis Wild mung beans and cultivated mung beans are actually quite clearly distinguished in terms of genetics. When analyzed with markers such as SNP, SV, and SSR, the two are basically classified into different groups, and the gene exchange between them is also very limited (Chen et al., 2015; Liu et al., 2022). Analysis tools such as PCA graphs and phylogenetic trees further verified this differentiation pattern. The population clustering of cultivated varieties is usually more concentrated, while the genetic background of wild species is more complex and the
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