Molecular-genetic mechanisms of regulation of growth habit in wheat

The vernalization requirement determines the need of plants in a prolonged period of cold treatment for transition from a vegetative to a reproductive phase. The vernalization response in wheat is controlled by the alleles of Vrn genes. A molecular structure and causes that are the basis of alternative alleles have been defined for almost all Vrn genes. Vrn1, Vrn2, and Vrn3 interact epistaticaly and form the positive feedback loop that is activated in winter wheat by the vernalization conditions. Vrn2 locus is a key element for flowering repression in winter wheat before vernalization, whereas Vrn1 mostly determines flowering time for spring varieties. In the present review, the studies of molecular mechanisms and genetic determination of pathways that regulate of growth habit (type of development) in wheat have been analyzed. The organization, structure, and functions of Vrn genes and their expression products are discussed in detail. Particular attention is paid to the structure of regulatory regions and the molecular mechanisms, which regulate of these genes' expression. The modern view on the model reflecting interaction between Vrn genes and the environmental during vernalization has been formulated.