Homoeologous Genes in <i>Triticum aestivum</i> L.: Structural Characteristics and Differential Activity
The paper is devoted to the comparative analysis of proteomic profiles and genotoxicity of common wheat ( Triticum aestivum L.), an important crop and one of the most complicated objects of study in genetics, cytogenetics, molecular genetics, and phylogenetics of plants. This cereal has an allohexaploid genome (2 n = 6 x = 42, AABBDD) formed by three diploid species Triticum urartu Thum. (AA), Aegilops speltoides Tausch. (SS), and Aegilops tauschii Coss. (DD). Copies of the same genes in the genomes A, B, and D are called homoeologous genes. It has been shown that most genes in the genome of T. aestivum are present as homoeologous copies that originate from a common ancestral gene. This review summarizes the current knowledge on the homoeologous genes of wheat. The structural and functional characteristics of certain groups of homoeologous wheat genes that encode the enzymes of biosynthesis of secondary metabolites and sterols, as well as autophagy proteins have been analyzed. Differential expression of these genes in various tissues and at different stages of ontogenesis or under different environmental conditions has been described. Different evolutionary consequences of the structural and functional divergence of homoeologous genes in polyploids may occur. Possible outcomes include: subfunctionalization, i.e., separation of functions between copies (co-expression of genes, inhibition/stimulation of transcription of certain homoeologs, as well as tissue-, organ-, and stage-specific expression); neofunctionalization can occur, where one gene may acquire new functions; pseudogenization, i.e., complete loss of function by one of the homoeologs, which subsequently becomes a pseudogene. Polyploid organisms have the advantage that they can display structural and functional divergence of homoeologous genes, which can increase the adaptive potential of the organism in a changing environment.