**DNA Methylation Profile of** β*-1,3-Glucanase* **and** *Chitinase* **Genes in Flax Shows Specificity Towards** *Fusarium Oxysporum* **Strains Di** ff**ering in Pathogenicity**

### **Wioleta Wojtasik 1,\*, Aleksandra Boba 1, Marta Preisner 1,2, Kamil Kostyn 1,2, Jan Szopa 1,2 and Anna Kulma 1**

1 Department of Genetic Biochemistry, Faculty of Biotechnology, University of Wroclaw, Przybyszewskiego 63, 51-148 Wroclaw, Poland; aleksandra.boba@uwr.edu.pl (A.B.); marta.preisner@upwr.edu.pl (M.P.); kamil.kostyn@upwr.edu.pl(K.K.);szopa@ibmb.uni.wroc.pl(J.S.);anna.kulma@uwr.edu.pl(A.K.)


Received: 2 September 2019; Accepted: 18 November 2019; Published: 20 November 2019

**Abstract:** Most losses in flax (*Linum usitatissimum* L.) crops are caused by fungal infections. The new epigenetic approach to improve plant resistance requires broadening the knowledge about the influence of pathogenic and non-pathogenic *Fusarium oxysporum* strains on changes in the profile of DNA methylation. Two contrasting e ffects on the levels of methylation in flax have been detected for both types of *Fusarium* strain infection: Genome-wide hypermethylation and hypomethylation of resistance-related genes (β*-1,3-glucanase* and *chitinase*). Despite the di fferences in methylation profile, the expression of these genes increased. Plants pretreated with the non-pathogenic strain memorize the hypomethylation pattern and then react more e fficiently upon pathogen infection. The peak of demethylation correlates with the alteration in gene expression induced by the non-pathogenic strain. In the case of pathogen infection, the expression peak lags behind the gene demethylation. Dynamic changes in tetramer methylation induced by both pathogenic and non-pathogenic *Fusarium* strains are dependent on the ratio between the level of methyltransferase and demethylase gene expression. Infection with both *Fusarium* strains suppressed methyltransferase expression and increased the demethylase (*demeter*) transcript level. The obtained results provide important new information about changes in methylation profile and thus expression regulation of pathogenesis-related genes in the flax plant response to stressors.

**Keywords:** flax; *Fusarium oxysporum*; pathogenic and non-pathogenic strains; sensitization; DNA methylation; PR genes
