Abstract
Flax crop yield is limited by various environmental stress factors, but the largest crop losses worldwide are caused by Fusarium infection. Polyamines are one of the many plant metabolites possibly involved in the plant response to infection. However, in flax plants the polyamine composition, genes involved in polyamine synthesis, and in particular their regulation, were previously unknown. The aim of this study was to investigate the polyamine synthesis pathway in flax and its involvement in response to pathogen infection. It is well established that polyamines are essential for the growth and development of both plants and fungi, but their role in pathogen infection still remains unknown. In our study we correlated the expression of genes involved in polyamine metabolism with the polyamine levels in plant tissues and compared the results for flax seedlings treated with two pathogenic and one non-pathogenic strains of Fusarium. We observed an increase in the expression of genes participating in polyamine synthesis after fungal infection, and it was reflected in an increase of polyamine content in the plant tissues. The highest level of mRNA was characteristic for ornithine decarboxylase during infection with all tested, pathogenic and non-pathogenic, Fusarium strains and the arginine decarboxylase gene during infection with the pathogenic strain of Fusarium culmorum. The main polyamine identified in the flax seedlings was putrescine, and its level changed the most during infection. Moreover, the considerable increase in the contents of cell wall-bound polyamines compared to the levels of free and conjugated polyamines may indicate that their main role during pathogen infection lies in strengthening of the cell wall. In vitro experiments showed that the polyamines inhibit Fusarium growth, which suggests that they play an important role in plant defense mechanisms. Furthermore, changes in metabolism and content of polyamines indicate different defense mechanisms activated in flax in response to infection by pathogenic and non-pathogenic Fusarium strains.
Highlights
Flax (Linum usitatissimum L.) is a valuable plant with a long history of cultivation
Identification of Flax Genes Involved in Polyamine Metabolism The aim of this study was to investigate the involvement of polyamines in the response to infection of flax with the pathogenic strains of F. culmorum and F. oxysporum and the non-pathogenic strain F. oxysporum Fo47
The remaining cDNA sequences encoding for the genes from polyamine metabolism were isolated by means of reverse transcription PCR with primers designed for the most homologous regions of the searched genes from other species, as this part of the experiment was performed before the flax genome was released
Summary
Flax (Linum usitatissimum L.) is a valuable plant with a long history of cultivation. It is a source of oil and fibers used in the pharmaceutical, cosmetics, food, paper, and textile industries. Flax’ polyamines during Fusarium infection advantage of flax is that the whole plant can be used, so it can be qualified as a no-waste, multipurpose plant. The competition with cotton as a source of fiber and rape as a source of oil caused a decrease in the cultivation of flax in recent years. As with other flax plant products, the decline in productivity caused by pathogen infection alters the yield and quality of flax fibers (Henriksson et al, 1997)
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