5. Jabs T, Dietrich RA, Dangl JL (1996) Initiation of runaway cell death in an Arabidopsis mutant by extracellular superoxide. Science 273: 1853–1856. 6. Gray WM (2002) Plant defence: a new weapon in the arsenal. Curr Biol 12: R352–R354. 7. Ward ER, Uknes SJ, Williams SC, Dincher SS, Wiederhold DL, et al. (1991) Coordinate gene activity in response to agents that induce systemic acquired resistance. Plant Cell 3: 1085–1094. 8. Gaffney T, Friedrich L, Vernooij B, Negrotto D, Nye G, et al. (1993) Requirement of salicylic acid for the induction of systemic acquired resistance. Science 261: 754–756. 9. Uknes S, Winter AM, Delaney T, Vernooij B, Morse A, et al. (1993) Biological induction of systemic acquired resistance in Arabidopsis. Mol Plant-Microbe Interact 6: 692–698. 10. Durrant WE, Dong X (2004) Systemic acquired resistance. Annu Rev Phytopathol 42: 185–209. 11. Kachroo A, Kachroo P (2006) Salicylic Acid-, Jasmonic Acid- and Ethylene- Mediated Regulation of Plant Defense Signaling. In Genetic Regulation of Plant Defense Mechanisms JaneSetlow, ed. Springer pubs 28: 55–83. 12. Kachroo P, Chandra-Shekara AC, Klessig D (2006) Plant signal transduction. and defense against viral pathogens. In: Advances in Viral Research Maramososch K, Shatkin AJ, eds. 66: 161–191. 13. Cao H, Glazebrook J, Clarke JD, Volko S, Dong X (1997) The Arabidopsis NPR1 gene that controls systemic acquired resistance encodes a novel protein containing ankyrin repeats. Cell 88: 57–63. 14. Ryals JA, Weymann K, Lawton K, Friedrich L, Ellis D, et al. (1997) The Arabidopsis NIM1 protein shows homology to the mammalian transcription factor inhibitor lkB. Plant Cell 9: 425–439. 15. Shah J, Tsui F, Klessig DF (1997) Characterization of a salicylic acid-insensitive mutant (sai1) of Arabidopsis thaliana, identified in a selective screen utilizing the SA-inducible expression of the tms2 gene. Mol Plant-Microbe Interact 1: 69–78. 16. Falk A, Feys BJ, Frost LN, Jones JD, Daniels MJ, et al. (1999) EDS1, an essential component of R gene-mediated disease resistance in Arabidopsis has homology to eukaryotic lipases. Proc Natl Acad Sci USA 96: 3292–3297. 17. Nawrath C, Heck S, Parinthawong N, Metraux JP (2002) EDS5, an essential component of salicylic acid-dependent signaling for disease resistance in Arabidopsis, is a member of the MATE transport family. Plant Cell 1: 275–286. 18. Wildermuth MC, Dewdney J, Wu G, Ausubel FM (2001) Isochorismate synthase is required to synthesize salicylic acid for plant defense. Nature 414: 562–565. 19. Jirage D, Tootle TL, Reuber TL, Frost LN, Feys BJ, et al. (1999) Arabidopsis thaliana PAD4 encodes a lipase-like gene that is important for salicylic acid signaling. Proc Natl Acad Sci USA 96: 13583–13588. 20. Glazebrook J (2001) Genes controlling expression of defense responses in Arabidopsis –2001 status. Curr Opin Plant Biol 4: 301–308. 21. Aarts N, Metz M, Holub E, Staskawicz BJ, Daniels MJ, et al. (1998) Different requirements for EDS1 and NDR1 by disease resistance genes define at least two R gene-mediated signaling pathways in Arabidopsis. Proc Natl Acad Sci USA 95: 10306–10311. 22. Bittner-Eddy PD, Beynon JL (2001) The Arabidopsis downy mildew resistance gene, RPP13-Nd, functions independently of NDR1 and EDS1 and does not require the accumulation of salicylic acid. Mol Plant-Microbe Interact 14: 416–421. 23. Chandra-Shekara AC, Navarre D, Kachroo A, Kang H-G, Klessig DF, et al. (2004) Signaling requirements and role of salicylic acid in HRT- and rrt- mediated resistance to turnip crinkle virus in Arabidopsis. Plant J 40: 647–659. 24. McDowell JM, Cuzick A, Can C, Beynon J, Dangl JL, et al. (2000) Downy mildew (Peronospora parasitica) resistance genes in Arabidopsis vary in functional requirements for NDR1, EDS1, NPR1 and salicylic acid accumu- lation. Plant J 6: 523–529. 25. Xiao S, Calis O, Patrick E, Zhang G, Charoenwattana P, et al. (2005) The atypical resistance gene, RPW8, recruits components of basal defence for powdery mildew resistance in Arabidopsis. Plant J 42: 95–110. 26. Feys BJ, Wiermer M, Bhat RA, Moisan LJ, Medina-Escobar N, et al. (2005) Arabidopsis SENESCENCE-ASSOCIATED GENE101 stabilizes and signals within an ENHANCED DISEASE SUSCEPTIBILITY1 complex in plant innate immunity. Plant Cell 9: 2601–2613. 27. Lipka V, Dittgen J, Bednarek P, Bhat R, Wiermer M, et al. (2005) Pre- and postinvasion defenses both contribute to nonhost resistance in Arabidopsis. Science 310: 1180–1183. 28. Vijayan P, Shockey J, Levesque CA, Cook RJ, Browse J (1998) A role for jasmonate in pathogen defence of Arabidopsis. Proc Natl Acad Sci USA 95: 7209–7214. 29. Kachroo P, Shanklin J, Shah J, Whittle EJ, Klessig DF (2001) A Fatty acid desaturase modulates the activation of defense signaling pathways in Plants. Proc Natl Acad Sci USA 98: 9448–9453. 30. Kachroo A, Lapchyk L, Fukushigae H, Hildebrand D, Klessig D, et al. (2003) Plastidial fatty acid signaling modulates salicylic acid- and jasmonic acid- mediated defense pathways in the Arabidopsis ssi2 mutant. Plant Cell 15: 2952–2965. 31. Kachroo A, Venugopal SC, Lapchyk L, Falcone D, Hildebrand D, et al. (2004) Oleic acid levels regulated by glycerolipid metabolism modulate defense gene expression in Arabidopsis. Proc Natl Acad Sci USA 101: 5152–5157. 32. Weber H (2002) Fatty acid derived signals in plants. Curr Opin Plant Biology 7: 217–224. Redundancy in Plant Defense 33. Li C, Liu G, Xu C, Lee GI, Bauer P, et al. (2003) The Tomato Suppressor of prosystemin-mediated responses2 Gene Encodes a Fatty Acid Desaturase Required for the Biosynthesis of Jasmonic Acid and the Production of a Systemic Wound Signal for Defense Gene Expression. Plant Cell 15: 1646–1661. 34. Yaeno T, Matsuda O, Iba K (2004) Role of chloroplast trienoic fatty acids in plant disease defense responses. Plant J 40: 931–941. 35. Xia Y, Gao Q-M, Yu K, Navarre D, Hildebrand D, et al. (2009) An intact cuticle in distal tissues is essential for the induction of systemic acquired resistance in plants. Cell Host & Microbe 5: 151–165. 36. Shah J, Kachroo P, Nandi A, Klessig DF (2001) A loss-of-function mutation in the Arabidopsis SSI2 gene confers SA- and NPR1-independent expression of PR genes and resistance against bacterial and oomycete pathogens. Plant J 25: 563–574. 37. Chandra-Shekara AC, Venugopal SC, Barman SR, Kachroo A, Kachroo P (2007) Plastidial fatty acid levels regulate resistance gene-dependent defense signaling in Arabidopsis. Proc Natl Acad Sci USA 104: 7277–7282. 38. Kachroo P, Kachroo A, Lapchyk L, Hildebrand D, Klessig D (2003a) Restoration of defective cross talk in ssi2 mutants; Role of salicylic acid, jasmonic acid and fatty acids in SSI2-mediated signaling. Mol Plant-Microbe Interact 11: 1022–1029. 39. Kachroo A, Shanklin J, Lapchyk L, Whittle E, Hildebrand D, et al. (2007) The Arabidopsis stearoyl-acyl carrier protein-desaturase family and the contribution of leaf isoforms to oleic acid synthesis. Plant Mol Biol 63: 257–271. 40. Kachroo P, Venugopal SC, Navarre DA, Lapchyk L, Kachroo A (2005) Role of salicylic acid and fatty acid desaturation pathways in ssi2-mediated signaling. Plant Physiol 139: 1717–1735. 41. Kachroo A, Daqi F, Havens W, Navarre R, Kachroo P, et al. (2008) Virus- induced gene silencing of stearoyl-acyl carrier protein-desaturase in soybean results in constitutive defense and enhanced resistance to pathogens. Mol Plant- Microbe Interact 21: 564–575. 42. Jiang CJ, Shimono M, Maeda S, Inoue H, Mori M, et al. (2009) Suppression of the rice fatty-acid desaturase gene OsSSI2 enhances resistance to blast and leaf blight diseases in rice. Mol Plant-Microbe Interact, In press. 43. Nawrath C, Me´traux JP (1999) Salicylic acid induction-deficient mutants of Arabidopsis express PR-2 and PR-5 and accumulate high levels of camalexin after pathogen inoculation. Plant Cell 11: 1393–1404. 44. Chen Z, Kloek AP, Boch J, Katagiri F, Kunkel BN (2000) The Pseudomonas syringae avrRpt2 gene product promotes pathogen virulence from inside plant cells. Mol Plant-Microbe Interact 13: 1312–1321. 45. Wiermer M, Feys BJ, Parker JE (2005) Plant immunity: the EDS1 regulatory node. Curr Opin Plant Biol 8: 383–389. 46. Bartsch M, Gobbato E, Bednarek P, Debey S, Schultze JL, et al. (2006) Salicylic acid-independent ENHANCED DISEASE SUSCEPTIBILITY1 signaling in Arabidopsis is regulated by the monooxygenase FMO1 and the nudix hydrolase NUDT7. Plant Cell 18: 1038–1051. 47. Xing D, Chen Z (2006) Effects of mutations and constitutive overexpression of EDS1 and PAD4 on plant resistance to different types of microbial pathogens. Plant Sci 171: 251–262. 48. Yang S, Hua J (2004) A haplotype-specific resistance gene regulated by BONZAI1 mediates temperature-dependent growth control in Arabidopsis. Plant Cell 16: 1060–1071. 49. Leeuwen HV, Kliebenstein DJ, West MAL, Kim K, Poecke RV, et al. (2007) Natural variation among Arabidopsis thaliana accessions for transcriptome response to salicylic acid. Plant Cell 19: 2099–2110. 50. Bouchabke O, Chang F, Simon M, Voisin R, Pelletier G, et al. (2008) Natural variation in Arabidopsis thaliana as a tool for highlighting differential drought responses. PLoS ONE 3(2): e1705. doi:10.1371/journal.pone.0001705. 51. Sandra SL, Amasino RM (1996) Ecotype-specific expression of a flowering mutant phenotype in Arabidopsis thaliana. Plant Physiol 111: 641–644. 52. Stokes TL, Kunkel BN, Richards EJ (2002) Epigenetic variation in Arabidopsis disease resistance. Genes Dev 16: 171–182. 53. Rodriguez-Rodriguez RA, Tabernero A, Velasco A, Lavado EM, Medina JM (2004) The neurotrphic effect of oleic acid includes dendritic differentiation and the expression of the neuronal basic helix-loop-helix transcription factor. J Neurochem 88: 1041–1051. 54. Stremmel W, Strohmeyer G, Borchard F, Kochwa S, Berk PD (1985) Isolation and partial characterization of a fatty acid binding protein in rat liver plasma membrane. Proc Natl Acad Sci USA 82: 4–8. 55. Svanborg C, Agerstam H, Aronson A, Bjerkvig R, Du¨ ringer C, et al. (2003) HAMLET kills tumor cells by an apoptosis-like mechanism-cellular, molecular, and therapeutic aspects. Adv Cancer Res 88: 1–29. 56. Menendez JA, Lupu R (2006) Oncogenic properties of the endogenous fatty acid metabolism: molecular pathology of fatty acid synthase in cancer cells. Curr Opin Clin Nutr Metab Care 9: 346–357. 57. Wang C, Wang X (2001) A novel phospholipase D of Arabidopsis that is activated by oleic acid and associated with the plasma membrane. Plant Physiol 127: 1102–1112. 58. Fox SR, Hill LM, Rawsthorne S, Hills MJ (2000) Inhibition of the glucose-6- phosphate transporter in oilseed rape (Brassica napus L.) plastids by acyl-CoA thioesters reduces fatty acid synthesis. Biochem J 352: 525–532. 59. Dempsey DA, Wobbe KK, Klessig DF (1993) Resistance and susceptible responses of Arabidopsis thaliana to turnip crinkle virus. Phytopathology 83: 1021–1029. PLoS Genetics | www.plosgenetics.org 17 July 2009 | Volume 5 | Issue 7 | e1000545