Flax (Linum usitatissimum L.) is a valuable agricultural crop, an important source of fiber and seeds necessary for industry and agriculture. The imperfect ascomycete Fusarium oxysporum is one of the most dangerous pathogens of flax. In the process of coevolution with plants, Fusarium oxysporum has developed several strategies at the molecular level to ensure successful infection. One such strategy is the use of small SIX effector proteins that facilitate infection and influence the hosts immune response. In our work, we investigated the relationship between the expression patterns of DIM2 methyltransferase, five SIX genes, and the virulence level in three contrasting Folini strains: highly virulent M139, medium-virulent F476, and weakly virulent F200. We found that Folini infection releases genes SIX1 and SIX13, which are exclusively associated with the parasitic stage of development, and genes whose activity is increased outside the plant in M139: SIX7ab, SIX10, SIX12ab. The greatest difference in the expression of SIX genes between the resistant and susceptible varieties was observed on the 5th day after inoculation with a highly virulent strain for the SIX12 and SIX13 genes, determining their possible role in the formation of the protective response of the resistant variety. We found a unique pattern of changes in the expression of the DIM2 DNA methyltransferase gene, with a high level at an early stage of infection development and a sharp drop on the seventh day. DIM2 activity also significantly differed between contrasting flax varieties in the early and late stages of infection.
Bankin et al. (Thu,) studied this question.