PLANT RESPONSE TO BIOTIC STRESS FACTORS

Plants are constantly exposed to attack by pathogenic fungi, bacteria and viruses which under unfavorable conditions can lead to abnormal growth and development, disease or even plant death. For this reason, plants have developed specific defense mechanisms. Innate immunity (physical and chemical barriers), present in the plant throughout its life even despite the lack of contact with pathogens divides into: nonspecific immunity, which provides an effective defense against different species and strains of pathogens and specific immunity, which determines the protection of specific, one type of plant in relation to one or more pathogenic strains. In contrast, acquired immunity, activated in the response to infection, it is activated in the cells surrounding the site of infection (local acquired immunity) or develops later in remote parts of the plant (systemic immunity induced and systemic acquired resistance). The first barrier protecting the plant from the infection is a physical barrier (the cell wall, a layer of wax, cuticle), while the second is a chemical barrier (anti-microbial compounds). The first stage of the plant defense response is to recognize elicitors: non-specific elicitors (DAMP, DAMP, MAMP) and specific elicitors (effectors). The recognition of non-specific elicitors by the host leads to the activation of primary immunity (PAMP'ami triggered immunity; PTI). However, pathogens can overcome the PTI resistance, and for this reason plants have developed a second line of defense, effectors triggered immunity (ETI). The next stage are sequentially occurring changes in cells: alkalization of the cytoplasm by rapid influx of calcium ions, production of reactive oxygen species and reactive forms of nitrogen, cascade of MAP kinases, which leads to the activation of transcription factors regulating expression of PR gene, ethylene production, JA and SA, strengthening of plants cell wall and the synthesis of antimicrobal compounds.