title: Physiological and transcriptional responses to osmotic stress of two Pseudomonas syringae strains that differ in epiphytic fitness and osmotolerance.
abstract: The foliar pathogen Pseudomonas syringae is a useful model for understanding the role of stress adaptation in leaf colonization. We investigated the mechanistic basis of differences in the osmotolerance of two P. syringae strains, B728a and DC3000. Consistent with its higher survival rates following inoculation onto leaves, B728a exhibited superior osmotolerance over DC3000 and higher rates of uptake of plant-derived osmoprotective compounds. A global transcriptome analysis of B728a and DC3000 following an osmotic upshift demonstrated markedly distinct responses between the strains; B728a showed primarily upregulation of genes, including components of the type VI secretion system (T6SS) and alginate biosynthetic pathways, whereas DC3000 showed no change or repression of orthologous genes, including downregulation of the T3SS. DC3000 uniquely exhibited improved growth upon deletion of the biosynthetic genes for the compatible solute N-acetylglutaminylglutamine amide (NAGGN) in a minimal medium, due possibly to NAGGN synthesis depleting the cellular glutamine pool. Both strains showed osmoreduction of glnA1 expression, suggesting that decreased glutamine synthetase activity contributes to glutamate accumulation as a compatible solute, and both strains showed osmoinduction of 5 of 12 predicted hydrophilins. Collectively, our results demonstrate that the superior epiphytic competence of B728a is consistent with its strong osmotolerance, a proactive response to an osmotic upshift, osmoinduction of alginate synthesis and the T6SS, and resiliency of the T3SS to water limitation, suggesting sustained T3SS expression under the water-limited conditions encountered during leaf colonization.
authors: Department of Plant Pathology & Microbiology, Iowa State University, Ames, Iowa, USA.
authors: Brian C
authors: BC
authors: Freeman
authors: Chiliang
authors: C
authors: Chen
authors: Xilan
authors: X
authors: Yu
authors: Lindsey
authors: L
authors: Nielsen
authors: Kelly
authors: K
authors: Peterson
authors: Gwyn A
authors: GA
authors: Beattie
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D016680:Genome, Bacterial; D009584:Nitrogen / Q000378:metabolism; D009997:Osmotic Pressure; D044224:Pseudomonas syringae / Q000145:classification* / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012965:Sodium Chloride / Q000737:chemistry / Q000494:pharmacology
chemical_list: D001426:Bacterial Proteins; D012965:Sodium Chloride; D009584:Nitrogen
references: J Bacteriol. 1994 Nov;176(22):6877-84
references: 7961447
references: Proc Natl Acad Sci U S A. 2013 Jan 29;110(5):E425-34
references: 23319638
references: J Bacteriol. 2007 Nov;189(22):8290-9
references: 17601783
references: Syst Appl Microbiol. 2000 Apr;23(1):31-40
references: 10879976
references: Appl Environ Microbiol. 1994 Jul;60(7):2568-74
references: 7915510
references: Mol Plant Pathol. 2002 Nov 1;3(6):451-60
references: 20569352
references: Cell. 2013 Feb 14;152(4):884-94
references: 23415234
references: J Bacteriol. 2013 May;195(10):2415-23
references: 23524610
references: Plant J. 2013 Sep;75(6):891-902
references: 23763788
references: Proc Natl Acad Sci U S A. 2003 Dec 23;100(26):15977-82
references: 14665692
references: Anal Biochem. 1973 Aug;54(2):484-9
references: 4269305
references: Appl Environ Microbiol. 2010 Mar;76(5):1574-86
references: 20038696
references: Mol Plant Microbe Interact. 2008 Jun;21(6):685-700
references: 18624633
references: mBio. 2013 Jun 11;4(3):e00334-13
references: 23760465
references: Mol Plant Microbe Interact. 1994 Nov-Dec;7(6):726-39
references: 7873779
references: Mol Microbiol. 2004 May;52(3):735-50
references: 15101980
references: J Bacteriol. 1996 Dec;178(23):6665-70
references: 8955280
references: J Lab Clin Med. 1954 Aug;44(2):301-7
references: 13184240
references: Environ Microbiol. 2010 Jun;12(6):1486-97
references: 20192963
references: J Proteome Res. 2008 Mar;7(3):1218-25
references: 18217705
references: J Bacteriol. 1992 Jun;174(11):3499-507
references: 1592805
references: Annu Rev Phytopathol. 2011;49:533-55
references: 21438680
references: Proc Natl Acad Sci U S A. 2008 Feb 26;105(8):3082-7
references: 18287070
references: BMC Bioinformatics. 2006 May 28;7:270
references: 16729895
references: Mol Plant Microbe Interact. 2009 Jul;22(7):857-67
references: 19522568
references: Appl Environ Microbiol. 1993 Feb;59(2):473-8
references: 8434912
references: Phytopathology. 2009 Jun;99(6):679-88
references: 19453226
references: Proc Natl Acad Sci U S A. 2000 Jun 6;97(12):6640-5
references: 10829079
references: Appl Environ Microbiol. 2010 Aug;76(16):5452-62
references: 20581190
references: Mol Microbiol. 2010 Jan;75(1):29-45
references: 19919675
references: Mol Plant Pathol. 2010 Nov;11(6):795-804
references: 21091602
references: Appl Environ Microbiol. 2005 Sep;71(9):5182-91
references: 16151103
references: J Bacteriol. 2006 Apr;188(7):2721-5
references: 16547062
references: Appl Environ Microbiol. 2011 Feb;77(4):1368-74
references: 21169432
references: Proc Natl Acad Sci U S A. 2010 Jul 13;107(28):12652-7
references: 20571117
references: Appl Environ Microbiol. 1994 Oct;60(10):3790-8
references: 16349417
references: Appl Environ Microbiol. 2011 May;77(10):3174-81
references: 21441337
references: Mol Biosyst. 2012 Jan;8(1):210-9
references: 21909508
references: Nature. 2000 Aug 31;406(6799):959-64
references: 10984043
references: Int J Syst Bacteriol. 1999 Apr;49 Pt 2:469-78
references: 10319466
references: J Bacteriol. 2008 Apr;190(8):2717-25
references: 18156257
references: J Bacteriol. 2010 Jul;192(14):3584-96
references: 20472799
references: Methods. 2001 Dec;25(4):402-8
references: 11846609
references: Microbiology (Reading). 2008 Feb;154(Pt 2):413-421
references: 18227245
references: Proc Natl Acad Sci U S A. 2004 Mar 2;101(9):3269-74
references: 14981249
references: J Biol Chem. 1994 Jan 21;269(3):1911-7
references: 7904996
references: PLoS One. 2013;8(3):e59388
references: 23527179
references: Proc Natl Acad Sci U S A. 2005 Aug 2;102(31):11064-9
references: 16043691
references: Mol Plant Microbe Interact. 2011 Jul;24(7):751-7
references: 21361789
references: Stat Appl Genet Mol Biol. 2004;3:Article3
references: 16646809
references: Mol Microbiol. 1999 Aug;33(4):712-20
references: 10447881
references: J Bacteriol. 2007 Oct;189(19):6901-12
references: 17660277
references: J Biol Chem. 2000 Feb 25;275(8):5668-74
references: 10681550
references: Nucleic Acids Res. 2011 Jan;39(Database issue):D596-600
references: 20929876
references: Appl Environ Microbiol. 2003 Feb;69(2):1220-8
references: 12571050