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- Title
AlgU contributes to the virulence of <italic>Pseudomonas syringae</italic> pv. <italic>tomato</italic> DC3000 by regulating production of the phytotoxin coronatine.
- Authors
Ishiga, Takako; Ishiga, Yasuhiro; Betsuyaku, Shigeyuki; Nomura, Nobuhiko
- Abstract
<italic>Pseudomonas syringae</italic> pv. <italic>tomato</italic> DC3000 (<italic>Pst</italic> DC3000), which causes bacterial speck disease of tomato, has been used as a model pathogen to investigate the molecular basis of plant-pathogen interactions. The function of many potential virulence factors encoded in the <italic>Pst</italic> DC3000 genome and their modes of action are not fully understood. <italic>P. syringae</italic> is known to produce the exopolysaccharide alginate. Although AlgU, a sigma factor, is known to regulate the expression of genes such as <italic>algD</italic> related to alginate biosynthesis, the molecular mechanisms of AlgU in the virulence of <italic>Pst</italic> DC3000 is still unclear. To investigate the function of AlgU and alginate in plant-bacterial pathogen interactions, we generated Δ<italic>algU</italic> and Δ<italic>algD</italic> mutants. After inoculation with Δ<italic>algU</italic> but not Δ<italic>algD</italic>, host plants of <italic>Pst</italic> DC3000 including tomato and <italic>Arabidopsis</italic> had milder disease symptoms and reduced bacterial populations. Expression profiles of <italic>Pst</italic> DC3000 genes revealed that AlgU can regulate not only the expression of genes encoding alginate biosynthesis, but also the expression of genes related to type III effectors and the phytotoxin coronatine (COR). We also demonstrated that the Δ<italic>algU</italic> mutant showed full virulence in the <italic>Arabidopsis fls2 efr1</italic> double mutant, which is compromised in the recognition of PAMPs. Further, the application of COR was able to restore the phenotype of the Δ<italic>algU</italic> mutant in the stomatal response. These results suggest that AlgU has an important role in the virulence of <italic>Pst</italic> DC3000 by regulating COR production.
- Subjects
TOMATO diseases &; pests; PSEUDOMONAS syringae; CORONATINE; VIRULENCE of bacteria; PLANT-pathogen relationships
- Publication
Journal of General Plant Pathology, 2018, Vol 84, Issue 3, p189
- ISSN
1345-2630
- Publication type
Article
- DOI
10.1007/s10327-018-0775-6