Ralstonia solanacearum extracellular polysaccharide is a specific elicitor of defense responses in wilt-resistant tomato plants.
Ralstonia solanacearum, which causes bacterial wilt of diverse plants, produces copious extracellular polysaccharide (EPS), a major virulence factor. The function of EPS in wilt disease is uncertain. Leading hypotheses are that EPS physically obstructs plant water transport, or that EPS cloaks the bacterium from host plant recognition and subsequent defense. Tomato plants infected with R. solanacearum race 3 biovar 2 strain UW551 and tropical strain GMI1000 upregulated genes in both the ethylene (ET) and salicylic acid (SA) defense signal transduction pathways. The horizontally wilt-resistant tomato line Hawaii7996 activated expression of these defense genes faster and to a greater degree in response to R. solanacearum infection than did susceptible cultivar Bonny Best. However, EPS played different roles in resistant and susceptible host responses to R. solanacearum. In susceptible plants the wild-type and eps(-) mutant strains induced generally similar defense responses. But in resistant Hawaii7996 tomato plants, the wild-type pathogens induced significantly greater defense responses than the eps(-) mutants, suggesting that the resistant host recognizes R. solanacearum EPS. Consistent with this idea, purified EPS triggered significant SA pathway defense gene expression in resistant, but not in susceptible, tomato plants. In addition, the eps(-) mutant triggered noticeably less production of defense-associated reactive oxygen species in resistant tomato stems and leaves, despite attaining similar cell densities in planta. Collectively, these data suggest that bacterial wilt-resistant plants can specifically recognize EPS from R. solanacearum.
Department of Plant Pathology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.
Annett
A
Milling
Lavanya
L
Babujee
Caitilyn
C
Allen
D005030:Ethylenes; D018551:Solanum lycopersicum / Q000276:immunology*; D010935:Plant Diseases / Q000382:microbiology; D057865:Plant Immunity; D011135:Polysaccharides, Bacterial / Q000276:immunology*; D043368:Ralstonia solanacearum / Q000737:chemistry / Q000472:pathogenicity*; D020156:Salicylic Acid; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology; D015854:Up-Regulation / Q000235:genetics; D037521:Virulence Factors
D005030:Ethylenes; D011135:Polysaccharides, Bacterial; D037521:Virulence Factors; C036216:ethylene; D020156:Salicylic Acid
Genome Biol. 2002 Jun 18;3(7):RESEARCH0034
12184808
Phytopathology. 2009 Oct;99(10):1127-34
19740025
Mol Plant Microbe Interact. 2003 Feb;16(2):141-8
12575748
Annu Rev Phytopathol. 2004;42:339-66
15283670
Mol Plant Microbe Interact. 2004 Jun;17(6):696-706
15195952
Plant Cell. 2009 Apr;21(4):1031-3
19395682
Appl Environ Microbiol. 1984 Jul;48(1):94-101
16346603
Curr Biol. 2008 Jul 22;18(14):1078-83
18639458
Biochem J. 1933;27(6):1824-8
16745305
Physiol Plant. 2009 Jul;136(3):324-35
19470092
Plant Mol Biol. 1993 Sep;22(6):1017-29
8400122
Plant J. 2003 Nov;36(4):485-99
14617079
Phytopathology. 1997 Dec;87(12):1264-71
18945028
Annu Rev Phytopathol. 2000 Sep;38:263-292
11701844
J Biol Chem. 1991 May 5;266(13):8312-21
2022648
Mol Plant Microbe Interact. 2000 Jan;13(1):6-13
10656580
Curr Opin Plant Biol. 2004 Oct;7(5):506-11
15337092
J Dairy Sci. 2006 Aug;89(8):2873-81
16840603
Plant Cell Physiol. 2003 Aug;44(8):803-10
12941872
Proc Natl Acad Sci U S A. 1995 May 9;92(10):4106-13
11607535
Phytopathology. 2005 Feb;95(2):136-43
18943982
Nature. 2002 Jan 31;415(6871):497-502
11823852
Genome Biol. 2007;8(2):R19
17291332
Plant Cell. 2006 Mar;18(3):764-79
16461584
Plant Physiol. 2005 Jul;138(3):1481-90
15937273
Gene. 1997 Mar 25;188(1):69-75
9099861
Appl Environ Microbiol. 1998 Dec;64(12):4918-23
9835583
Plant Cell. 2007 Mar;19(3):890-903
17351116
Mol Plant Microbe Interact. 2006 Sep;19(9):1023-33
16941906
Proc Natl Acad Sci U S A. 2002 Feb 19;99(4):2404-9
11842188
Nature. 2006 Nov 16;444(7117):323-9
17108957
Mol Plant Microbe Interact. 2008 Sep;21(9):1261-70
18700830
Mol Plant Pathol. 2002 May 1;3(3):111-8
20569316
Phytopathology. 2002 Oct;92(10):1142-8
18944225
Nat Rev Immunol. 2006 Nov;6(11):849-58
17024229
Annu Rev Phytopathol. 1995;33:173-97
18999958
Phytopathology. 1999 Dec;89(12):1233-9
18944650
Biochem J. 1959 Sep;73:127-32
14416360
Mol Plant Microbe Interact. 1997 Jul;10(5):624-34
9204567
Trends Microbiol. 2004 Dec;12(12):555-61
15539115
Annu Rev Phytopathol. 2006;44:135-62
16602946
Annu Rev Phytopathol. 2005;43:83-116
16078878
Mol Plant Microbe Interact. 2006 Jan;19(1):69-79
16404955
Curr Opin Plant Biol. 2009 Aug;12(4):414-20
19608450