R-proteins, also known as resistance proteins, refer to a class of proteins found in plants that play a crucial role in their defense mechanism against pathogens such as bacteria, viruses, and fungi. These proteins are an important component of the plant's immune system and help to initiate a rapid and effective defense response to protect the plant from infection.
R-proteins are encoded by specific genes within the plant's genome and are usually present in a single copy. They feature a characteristic domain known as the nucleotide-binding site (NBS) and leucine-rich repeats (LRR), which is involved in recognizing and binding to pathogen-derived molecules called effectors. This recognition triggers a series of signal transduction events leading to the activation of defense responses.
Upon pathogen recognition, R-proteins can activate various defense pathways, including the hypersensitive response (HR) and systemic acquired resistance (SAR). The HR is a rapid cell death at the infection site, preventing the further spread of pathogens, while SAR is a systemic defense mechanism that enhances the resistance of distant plant parts to subsequent pathogen attacks.
R-proteins show a high degree of diversity and specificity, as different R-proteins recognize different pathogen effectors. This diversity allows plants to detect and defend against a wide range of pathogenic invaders. However, pathogens can evade detection by mutating their effectors, which leads to the arms race between plants and their pathogens.
Overall, R-proteins are crucial for plant defense and represent a key target for studying plant-pathogen interactions and developing disease-resistant crop varieties.
