Pseudomonas syringae Genomics Provides Important Insights to Secretion Systems, Effector Genes and the Evolution of Virulence
D.L. Arnold, S.A.C. Godfrey and R. W. Jackson
from: Plant Pathogenic Bacteria: Genomics and Molecular Biology (Edited by: Robert W. Jackson). Caister Academic Press, U.K. (2009)
The start of the 21st Century was a watershed for Pseudomonas syringae genomics, with the completion of three genome sequences for different P. syringae pathovars. The release of these sequences permitted a series of investigations designed at unraveling the biology of this group of plant pathogens. One area that has benefited has been the identification of different secretion systems and their substrate effectors; some of these secretion systems can deliver proteins into the plant environment to subvert the plants' resistance machinery and to gain access to plant nutrients. The most investigated secretion system in P. syringae is the type III system which delivers effector proteins into the plant cytoplasm to disrupt the plantsŐ cellular pathways, including signaling mechanisms that would otherwise trigger defence mechanisms. The genome sequences have been analysed to predict the number of effector genes present in the different strains, gain insights into the function of these proteins and examine how the bacteria can evolve and change its effector repertoire in order to overcome plant resistance. There is still much scope for further analysis, particularly of poorly understood secretion systems. For example, very little is known about the role of non-type III secretion systems in P. syringae. Indeed, the genome sequences have allowed us to identify putative orthologues of the vas-vgr type VI system in P. syringae and intriguingly there appears to be some variation in gene content and synteny between the pathovars read more ...