Legume Genomics and Genetics 2024, Vol.15, No.1, 37-44 http://cropscipublisher.com/index.php/lgg 38 advancing our knowledge of plant evolution and for improving legume breeding strategies to enhance crop resilience and productivity. 2 Whole Genome Duplication 2.1 Mechanisms of WGD Whole genome duplication (WGD) is a significant evolutionary event that results in the doubling of an organism's entire genome. This process can occur through two primary mechanisms: autopolyploidy and allopolyploidy. Autopolyploidy involves the duplication of a genome within a single species, leading to multiple sets of chromosomes that are identical. In contrast, allopolyploidy results from the hybridization between two different species, followed by chromosome doubling, which combines the genomes of both parent species (McGrath and Lynch, 2012; Ren et al., 2018). The molecular and genetic basis of WGD involves complex processes that include errors in meiosis or mitosis, leading to the formation of polyploid cells. These errors can be due to the failure of chromosome segregation or cytokinesis, resulting in cells with double the normal chromosome number. The retention of duplicated genes following WGD is influenced by several factors, including dosage balance constraints, which favor the maintenance of gene duplicates to preserve the balance of gene products (McGrath and Lynch, 2012). 2.2 Evolutionary consequences of WGD The evolutionary consequences of WGD are profound and multifaceted. One of the primary outcomes is gene duplication, which provides raw material for evolutionary innovation. Duplicated genes can undergo various fates, including pseudogenization (loss of function), neofunctionalization (acquisition of new functions), and subfunctionalization (partitioning of the original function between duplicates) (McGrath and Lynch, 2012; Ren et al., 2018). These processes contribute to functional diversification and can lead to the evolution of new traits and adaptations. WGD also impacts genome structure and stability. The presence of duplicated genes can lead to genomic rearrangements and changes in chromosome structure, which may affect genome stability. However, the retention of duplicated genes can also enhance genome robustness by providing redundancy and buffering against deleterious mutations (McGrath and Lynch, 2012). Furthermore, WGD plays a crucial role in speciation and adaptation. The loss of duplicate genes following WGD can lead to reproductive isolation between populations, thereby increasing the speciation rate. This process is particularly significant in polyploid lineages, where WGD can drive rapid diversification and adaptation to new environments (McGrath and Lynch, 2012; Ren et al., 2018). The preferential retention of genes involved in essential cellular functions and metabolic pathways following WGD suggests that these events can enhance the adaptive potential of species, allowing them to thrive in changing environmental conditions (Ren et al., 2018). In summary, WGD is a pivotal evolutionary mechanism that drives gene duplication, functional diversification, and species diversification. Its impact on genome structure, stability, and adaptation underscores its significance in the evolutionary history of legumes and other angiosperms. 3 Historical WGD Events in Legumes 3.1 Identification of WGD events in legumes Whole genome duplication (WGD) events in legumes have been identified using a variety of genomic and phylogenomic methods. Comparative genomic analyses, which involve comparing the genomes of different species to identify duplicated regions, are commonly used. Phylogenomic analyses, which construct phylogenetic trees from gene family data, help in pinpointing the timing and occurrence of WGDs. For instance, one study utilized comparative genomic and phylogenomic analyses of 59 public genomes/transcriptomes and 46 newly sequenced transcriptomes to detect large-scale gene duplication events in angiosperms, including
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