The plant immune system

An understanding of the immune system of plants is important for progress in agriculture and pest control. Lacking the mobile defender cells and adaptive immune response found in mammals, plants rely on the innate immunity of each cell and on signals sent around the plant from infection sites. Jonathan Jones and Jeffery Dangl review current models of plant defences, and identify some of the remaining unknowns, including the mechanism used to arrest growth in pathogens. Many plant-associated microbes are pathogens that impair plant growth and reproduction. Plants respond to infection using a two-branched innate immune system. The first branch recognizes and responds to molecules common to many classes of microbes, including non-pathogens. The second responds to pathogen virulence factors, either directly or through their effects on host targets. These plant immune systems, and the pathogen molecules to which they respond, provide extraordinary insights into molecular recognition, cell biology and evolution across biological kingdoms. A detailed understanding of plant immune function will underpin crop improvement for food, fibre and biofuels production.