Submitted to: Molecular Plant-Microbe Interactions
Publication Type: Review Article
Publication Acceptance Date: 9/15/2006
Publication Date: 11/1/2006
Citation: Lindeberg, M., Cartinhour, S.W., Myers, C., Schechter, L., Schneider, D.J., Collmer, A. 2006. Closing the circle on the discovery of genes encoding Hrp regulon members and type III secretion system effectors in the genomes of three model Pseudomonas syringae strains. Molecular Plant-Microbe Interactions. 19(11):1151-1158. Interpretive Summary:
Technical Abstract: Pseudomonas syringae strains translocate large and distinct collections of effector proteins into plant cells via the type III secretion system (T3SS). P. syringae effectors are designated Hop (Hrp outer protein) or Avr (avirulence) proteins. Some Hop proteins are considered to be extracellular T3SS helpers acting at the plant-bacterium interface. Identification of complete sets of effectors and related proteins has been enabled by the application of bioinformatic and high-throughput experimental techniques to the complete genome sequences of three model strains: P. syringae pv. tomato DC3000, P. syringae pv. phaseolicola 1448A, and P. syringae pv. syringae B728a. Several recent papers, including three in this issue of Molecular Plant-Microbe Interactions, address the effector inventories of these strains. These studies establish that active effector genes in P. syringae are expressed by the HrpL alternative sigma factor and can be predicted on the basis of cis Hrp promoter sequences and N-terminal amino-acid patterns. Among the three strains analyzed, P. syringae pv. tomato DC3000 has the largest effector inventory and P. syringae pv. syringae B728a has the smallest. Each strain has several effector genes that appear inactive. Only five of the 46 effector families that are represented in these three strains have an active member in all of the strains.