The possible role of pr proteins in multigenic and induced systemic resistance

Abstract

6.6 Conclusion: Timely accumulation of PR proteins during pathogenesis can be suggested as a part of defense mechanisms in plants against pathogens and pests. Some of these proteins may have a different role in plant metabolism and/or may just occur there as a part of regulatory systems overall happening during the plant-pathogen interactions. Specific isozymes of the hydrolytic enzymes, on the other hand, which demonstrate differential activity toward the substrate during the release of elicitor molecules from the pathogens may have been evolved as a part of defense mechanisms in naturally resistant plants. Such isozymes may be bred into the resistant lines of crop varieties act as recognition mechanism to initiate the whole battery of defense mechanisms. It is also clear that some of PR-proteins such as osmotins and hydrolytic enzymes have a direct involvement in reduction of pathogenesis as evidenced by genetic studies as well as microscopic observations. However, it is important to recognize that plant defense mechanisms are complex and more than one factor is involved in the successful existence of plant species over the centuries under the abundance of numerous organisms that can be potentially harmful to plants. Nevertheless pathogenesis is an exception, and is a result of failure of many pathways to be activated in a timely manner. PR proteins are certainly there for a reason, whether they are a part of a major defense mechanisms or not, according to the inducer, they are a part of induced systemic resistance and more studies will further show that they may be the reason of successful breeding efforts, which we have been doing over the centuries to breed disease resistant varieties carrying more than one gene for resistance.