Arachidonic and Eicosapentaenoic Acids, Glucans and Calcium as Regulators of Resistance to a Plant Disease
A common response of plants, often associated with disease resistance, is the localized and rapid death of plant cells at the infection site. This reaction, referred to as a hypersensitive response (HR), includes the accumulation of phytoalexins (low molecular weight compounds which inhibit microbial development). In some plant-parasite interactions, different races of a pathogen can be distinguished by the type of response they elicit in different cultivars. Incompatible races of Phytophthora infestans elicit the accumulation of sesquiterpenoid phytoalexins, principally rishitin and lubimin, in tubers of resistant (R-gene) cultivars faster to higher levels following infection than do compatible races on susceptible cultivars.1,2 Bostock et al.3 reported that arachidonic acid (AA) and eicosapentaenoic acid (EPA) isolated from mycelium of P. infestans elicited the accumulation of rishitin and lubimin in potato discs. However, incompatible and compatible races of P. infestans do not differ in the quantity of these fatty acids. Thus, AA and EPA per se are not the determinants of race specificity in the potato-P. infestans interaction, but they constitute a major component of the “native” fungal elicitor; i.e., the part of the fungus which is “recognized” by the plant and is responsible for eliciting HR and phytoalexin accumulation. It is unclear how contact between an elicitor, such as AA, and potato tuber cells elicits these defense mechanisms.
KeywordsArachidonic Acid Potato Tuber Hypersensitive Response Phytophthora Infestans Plant Pathol
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