Formation of plant resistance to pathogens involving epigenetic factors and phytohormones

Abstract

The development of resistance to plant pathogens is determined by the presence of resistance genes and regulation of their activity due to phytohormones, the activity of the nuclear pore complex, and epigenetic modifications at the post-transcriptional and post-translational levels of DNA and histones, respectively. Changes in gene expression due to such modifications can be inherited in generations and contribute to the selection of resistant plants in populations.The nuclear pore complex is composed of nucleoporins, a nuclear pore basket, cytoplasmic filaments and is able to selectively transport transcription factors to the nucleus from the cytoplasm and mRNA in the opposite direction, affecting gene expression. Methylation is the most common and well-studied among the epigenetic modifications. It is described for DNA and histones and ensures genome stability and the availability of transcription factors. Incorporation of methyl groups to amino acid residues is not always a factor in gene silencing for histones. The number of the incorporated groups as well as an amino acid they are attached to are crucial. Histone acetylation is associated with the transition to transcriptional activity.The general control histone acetyltransferase TaGCN5 is able to promote expression of the enoyl-CoA reductase gene in allohexaploid wheat, which is involved in the biosynthesis of cuticular wax as one of the resistance factors. The reverse process of deacetylation acts both as a positive regulator, through ethylene response factors, and a negative one, as it interferes with acetylation and methylation of histone amino acids. Jasmonic and salicylic acids, along with combinations of the mentioned phytohormones, mediate formation of systemic acquired resistance in addition to ethylene. Auxin is a positive phytohormone for pathogens due to its ability to influence the structure of the cell wall. At the same time, pathogens, due to effectors, are able to inhibit the plant’s immune responses, so there is a constant “arms race” resulting in the selection of more effective means of penetration and development in the plant as well as its protective reactions. Investigation of the mechanisms of resistance formation and identifying the main factors of resistance, such as either presence of a gene sequence and/or factors regulating its expression, are of great importance.