Genes may prevent Septoria tritici blotch disease in wheat
Wheat is the most important UK crop with an annual value of about £1.2 billion. One of the most economically important diseases of wheat is Septoria leaf blotch also known as Septoria tritici blotch (STB). The disease is caused by the fungus Mycosphaerella graminicola (Mg) and it is a major threat to crop yields in the UK and worldwide. Rothamsted researchers, who receive strategic funding from the BBSRC, have previously identified a fungal gene that is critical in evading wheat immune responses early during disease establishment. Now, using modern biotechnology methods two wheat genes have been identified whose functions are to activate the wheat defence response. This finding can pave the road for developing molecular approaches to combat the disease in the future. The study has been published in the journal Molecular Plant-Microbe Interactions.
When pathogens attack wheat plant leaves they release signals that the plants have evolved to recognise and subsequently initiate a response within the leaf cells to protect themselves against the pathogen. However, pathogens are successful in evading the immune response of the host plant because they have also evolved other signals that are able to suppress the first layer of plant defence, often making themselves “invisible.”
The most commonly known and studied fungal signal that both plants and animals can recognise is chitin, which is a major component of fungal cell walls. In some plants, like Arabidopsis, just one gene that codes for the protein Chitin Elicitor Receptor Kinase 1 (CERK1) is sufficient for recognition of fungal chitin and initiation of defence responses. In other plants, e.g. rice, not only CERK1 but also another gene encoding a different protein, Chitin Elicitor Binding Protein (CEBiP), are required. Despite the fact that wheat is a major crop in the UK and STB a highly prevalent disease, very little was known about the mechanism that wheat may have evolved to recognise the invading fungus. This study demonstrates that wheat is more like rice, having a two gene system for recognition of fungal chitin and elicitation of the immune response. Moreover, these genes are capable of conferring resistance against STB in the absence of the interfering fungal gene.
Kostya Kanyuka, Ph.D., lead researcher at Rothamsted said: “We are very excited about the findings of this study. To identify the exact role of the two candidate wheat genes we had to temporarily inhibit their function (i.e. silence) and investigate whether the pathogens can be successful or not in causing disease in the silenced plants. Virus-induced gene silencing (VIGS) is a powerful method used in plant science for inhibiting plant gene function for a short period of time. In this study we demonstrate that gene silencing using this method can also have long lasting effects, thus allowing the study of plant-pathogen interactions that have a long symptomless infection phase, like Mycosphaerella graminicola in wheat”.