Part G - Plant Resistance Flashcards
Discuss what you know about plant resistance genes that have been identified at a molecular level and how the proteins they produce interact with plant pathogens.
R genes are essential for plant health. They provide resistance to a wide range of plant pathogens, including bacteria, fungi, and viruses. R genes are also used in plant breeding programs to develop crops that are resistant to disease.
For examples:
Pto gene - confers resistance to the late blight pathogen, Phytophthora infestans
Rpp1 gene - confers resistance to the powdery mildew pathogen, Blumeria graminis
Cf-9 gene - confers resistance to the black spot pathogen, Septoria tritici
R genes are an important part of the plant immune system. They play a vital role in protecting plants from disease.
In the interaction of plants with their pathogens, two levels of plant recognition of the pathogen are considered to occur; an initial basal recognition followed by a more specific recognition of the pathogen.
Giving examples, discuss the theory used to describe these two steps, noting how the specific recognition is influenced by the selection pressure on the pathogen population.
Basal recognition is the first line of defense against pathogens. It is a non-specific response that is triggered by the presence of any pathogen, regardless of its identity.
Specific recognition is the second line of defense against pathogens. It is a more specific response that is triggered by the presence of a pathogen that the plant has previously encountered. This is mediated by resistance genes (R genes), which are genes that encode proteins that recognize specific pathogen-derived molecules (PDMs)
As pathogens evolve, they can develop new PDMs that can evade the recognition of R genes. This can lead to the development of new plant diseases. However, plants can also evolve new R genes that can recognize new PDMs. This is an ongoing arms race between plants and pathogens.
Example
Potato leafroll virus (PLRV) is a virus that infects potatoes. PLRV is a non-specific pathogen, so it can be detected by the basal recognition system of potatoes. However, PLRV can also produce PDMs that can be recognized by specific R genes in potatoes. This is why some varieties of potatoes are resistant to PLRV, while others are susceptible.
