title: Coronatine Gene Expression In Vitro and In Planta, and Protein Accumulation During Temperature Downshift in Pseudomonas syringae.
abstract: The plant pathogenic bacterium Pseudomonas syringae PG4180 synthesizes high levels of the phytotoxin coronatine (COR) at the virulence-promoting temperature of 18 °C, but negligible amounts at 28 °C. Temperature-dependent COR gene expression is regulated by a modified two-component system, consisting of a response regulator, CorR, the histidine protein kinase CorS, and a third component, termed CorP. We analyzed at transcriptional and translational levels the expression of corS and the cma operon involved in COR biosynthesis after a temperature downshift from 28 to 18 °C. Expression of cma was induced within 20 min and increased steadily whereas corS expression was only slightly temperature-dependent. Accumulation of CmaB correlated with accumulation of cma mRNA. However, cma transcription was suppressed by inhibition of de novo protein biosynthesis. A transcriptional fusion of the cma promoter to a promoterless egfp gene was used to monitor the cma expression in vitro and in planta. A steady induction of cma::egfp by temperature downshift was observed in both environments. The results indicate that PG4180 responds to a temperature decrease with COR gene expression. However, COR gene expression and protein biosynthesis increased steadily, possibly reflecting adaptation to long-term rather than rapid temperature changes.
authors.affiliation: Jacobs University Bremen, School of Engineering and Science, Campus Ring 1, 28759 Bremen, Germany; E-Mails:  angelasmirnova@hotmail.com  (A.V.S.);  h.weingart@jacobs-university.de  (H.W.);  a.schenk@jacobs-university.de  (A.S.);  m.ullrich@jacobs-university.de  (M.S.U.).
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Braun
authors.forename: Angela V
authors.initials: AV
authors.lastname: Smirnova
authors.forename: Helge
authors.initials: H
authors.lastname: Weingart
authors.forename: Alexander
authors.initials: A
authors.lastname: Schenk
authors.forename: Matthias S
authors.initials: MS
authors.lastname: Ullrich