Molecular determinants of plant-parasite interaction
Tomato crops worldwide are being threatened by wilt and canker disease caused by the gram-positive Cmm bacterium. The molecular mechanisms underlying successful Cmm infection of tomato are, however, poorly understood. To study this interaction between the Cmm bacterium and the tomato, the CMM-Tomato Interact project is following a proteomics approach. Scientists have analysed the proteins from tomato plants infected with the wild type and the endophytic Cmm strains and have compared them to the protein levels of control plants. Thousands of proteins have so far been identified of both host and parasite origin and have helped project partners draw a picture of the infection process. Results indicate that the plant is capable of sensing the invading bacterium and mounts a basal defense response, which most of the times is inadequate to clear the invading parasite. Project scientists found an important determinant of disease symptom development in tomato, namely the Aminocyclopropanecarboxylate (ACC) oxidase enzyme. ACC is implicated in the biosynthesis of ethylene which is used by plants for fruit ripening. From the bacterial perspective, data show that the Cmm bacterium is capable of monitoring the plant conditions, transducing signals and secreting hydrolytic enzymes aimed at degrading plant components. Two putative transcription regulators have also been identified that are involved in the Cmm bacterial infectivity. The identification of such Cmm virulence proteins, combined with the discovery of tomato proteins important for Cmm defense, have the potential to lead to the development of tomato varieties with less susceptibility to Cmm. This will reduce tomato crop losses and boost agriculture-related economies.