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Salicylic Acid and Systemic Acquired Resistance Play a Role in Attenuating Crown Gall Disease Caused by Agrobacterium tumefaciens
Ajith Anand, Srinivasa Rao Uppalapati, Choong-Min Ryu, Stacy N. Allen, Li Kang, Yuhong Tang and Kirankumar S. Mysore
Vol. 146, No. 2 (Feb., 2008), pp. 703-715
Published by: American Society of Plant Biologists (ASPB)
Stable URL: http://www.jstor.org/stable/40065875
Page Count: 13
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We investigated the effects of salicylic acid (SA) and systemic acquired resistance (SAR) on crown gall disease caused by Agrobacterium tumefaciens. Nicotiana benthamiana plants treated with SA showed decreased susceptibility to Agrobacterium infection. Exogenous application of SA to Agrobacterium cultures decreased its growth, virulence, and attachment to plant cells. Using Agrobacterium whole-genome microarrays, we characterized the direct effects of SA on bacterial gene expression and showed that SA inhibits induction of virulence (vir) genes and the rep ABC operon, and differentially regulates the expression of many other sets of genes. Using virus-induced gene silencing, we further demonstrate that plant genes involved in SA biosynthesis and signaling are important determinants for Agrobacterium infectivity on plants. Silencing of ICS (isochorismate synthase), NPR1 (nonexpresser of pathogenesis-related gene 1), and SABP2 (SA-binding protein 2) in N. benthamiana enhanced Agrobacterium infection. Moreover, plants treated with benzo-(1,2,3)-thiadiazole-7-carbothioic acid, a potent inducer of SAR, showed reduced disease symptoms. Our data suggest that SA and SAR both play a major role in retarding Agrobacterium infectivity.
Plant Physiology © 2008 American Society of Plant Biologists (ASPB)