- Selcuk Journal of Agriculture and Food Sciences
- Vol: 19 Issue: 35
- Role of Host Enzymes in Plant Disease Resistance
Role of Host Enzymes in Plant Disease Resistance
Authors : Nuh Boyraz, Selçuk Delen
Pages : 51-59
View : 11 | Download : 16
Publication Date : 2005-04-25
Article Type : Research Article
Abstract :Some of the host enzymes play an important role in disease resistance. Glucanase and chitinase, two enzymes which are mostly of host origin, lyse the mycelia of fungal pathogens, as glucans and chitin are the major components of the cell wall of most fungi. These enzymes cause more lysogeny in resistant plants. 1,3-β-Glucanase activity may increase severalfold more in resistant varieties than in susceptible varieties as envisaged in muskmelon. However, these enzymes need not be involved in the disease-resistance mechanism in all host-pathogen systems. Peroxidase is another host enzyme which is frequently correlated with disease resistance. The exact mode of action of this enzyme is not known. It is an important enzyme in the synthesis of lignin, and it catalyzes the oxidation of phenolics into more toxic quinones. Polyphenoloxidase has a similar activity to that of peroxidase. The enzyme activity leads to the synthesis of quinones and tanins which are highyl toxic to microorganisms. Phenylalanine ammonia lyase (PAL) is the key enzyme for the synthesis of phenolics, phytoalexins, and lignin. İnhibition of PAL by selective inhibitors leads to susceptibilty in resistant tissues, suggesting the importance of this enzyme in disease resistance β-Glicosidase is the important host enzyme which is activated after infection. This enzyme converts the nontoxic glicosides into phenolics, which are inhibitory to pathogens. Thus, β-glycosidase also plays an important role in disease resistance. An interesting relation between esterases and disease resistance has been observed. The superoxide anion-generating NADPH oxidase system has been found to induce resistance. Digitonin, a steroid glycoalcoloid, activates this system in many plants and induces resistance.Keywords : Dayanıklılık, bitki hastalıkları, enzimler