This Article Full Text (PDF) Other Versions of this Article: AEM.01770-06v1 73/4/1079    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Yang, S. Articles by Yang, C.-H. Search for Related Content PubMed PubMed Citation Articles by Yang, S. Articles by Yang, C.-H. Agricola Articles by Yang, S. Articles by Yang, C.-H.

 Previous Article  |  Next Article 

Appl. Environ. Microbiol. doi:10.1128/AEM.01770-06
Copyright (c) 2006, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Global effect of Indole-3-acetic acid (IAA) biosynthesis on multiple virulence factors of Erwinia chrysanthemi 3937

Department of Biological Sciences, University of Wisconsin-Milwaukee, WI 53211, U.S.A.; Department of Plant Pathology, Nanjing Agricultural University, Nanjing, CHINA; Department of Plant Pathology, University of Wisconsin-Madison, WI 53706, U.S.A.; Department of Biology, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1; USDA-ARS-George E. Brown Jr. Salinity Lab., Riverside, CA 92507, U.S.A.; Department of Plant Pathology, University of California-Riverside, CA 92521, U.S.A

^* To whom correspondence should be addressed. Email: chyang{at}uwm.edu.

	Abstract

Production of the plant hormone indole-3-acetic acid (IAA) is widespread among plant-associated microorganisms. The non-gall-forming phytopathogen Erwinia chrysanthemi 3937 (Ech3937) possesses iaaM (ASAP16562) and iaaH (ASAP16563) gene homologues. In this work, the null knockout iaaM mutant Ech138 was constructed. The IAA production of Ech138 was reduced in M9 minimal medium (MM) supplemented with L-tryptophan. Compared with wild-type Ech3937, Ech138 exhibited reduced ability to produce local maceration but the multiplication in Saintpaulia ionantha was unaffected. The pectate lyase production of Ech138 was diminished. Compared with wild-type Ech3937, the expression level of an oligogalacturonate lyase, ogl, and three endo-pectate lyases, pelD, pelI, and pelL, was reduced in Ech138 using a green fluorescent protein (GFP)-based fluorescence activated cell sorter (FACS) promoter activity assay. In addition, the transcription of type III secretion system (T3SS) genes, dspE (a putative T3SS effector) and hrpN (T3SS harpin), was found to be diminished in the iaaM mutant Ech138. Compared with Ech3937, a reduced expression of hrpL (a T3SS alternative sigma factor) and gacA but an increased expression of rsmA in Ech138 were also observed suggesting the regulation of T3SS and pectate lyase genes by the IAA biosynthesis might be partially due to the post-transcriptional regulation of the Gac-Rsm regulatory pathway.