Plants and animals respond to MAMPs (microbe-associated molecular patterns). MAMP-activated response pathways are functionally analogous to mammalian TLR-signaling. A high throughput Arabidopsis seedling assay allowed us to make several important discoveries. First, bacterial flagellin (Flg22) elicits the deposition of callose in cotyledons via a pathway that involves the transcription factor MYB51, ethylene signaling, and the synthesis of indole glucosinolates that function as novel secondary messengers. Second, bacterial elongation factor EF-Tu (Efl26) and Flg22 elicit callose production by distinct pathways. Third, Flg22, but not oligogalacturonides (OGs), elicit the production of soluble anti-microbial compound(s). Fourth, the bacterial phytopathogen Pseudomonas syringae blocks MAMP signaling in roots by the production of the jasmonic acid (JA) mimic coronatine. In addition, we have also shown:1) that cell-wall associated peroxidases play a key role in the plant defense response, 2) that infection of Arabidopsis by the opportunistic broad host range pathogen Pseudomonas aerugionsa involves novel cell wall degrading enzymes, and 3) that the insect leaf miner Scaptomyza graminum, which is nested in the Drosophila phylogenetic clade, is an aggressive Arabidopsis herbivore. In the second round of MERIT funding: We will investigate how MAMP-activated pathways relate to defense pathways mediated by salicylic acid, JA and ET. We will determine the molecular mechanism by which coronatine blocks MAMP signaling. Using MYB51 as a model, we will identify the set of proteins required to activate MYB51-responsive promoters. We will identify the soluble antimicrobial factors elicited by MAMPs and elucidate the signaling pathway(s) leading to their synthesis. We will distinguish the roles that peroxidases and NADPH oxidases play in plant defense and use the Scaptomyza model to determine the role of the oxidase burst in insect defense. We will identify P. aeruginosa cell wall degrading enzymes and determine the role(s) they play in plant pathogenesis.
Although adaptive immunity is unique to vertebrates, the innate immune response has ancient origins. Common features of innate immunity in plants and animals include defined receptors for microbe-associated molecules, conserved MAPK signaling cascades, and the production of anti-microbial peptides and compounds. Studying innate immunity in non-vertebrates enhances our understanding of human immunity.
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|O'Brien, Jose A; Daudi, Arsalan; Finch, Paul et al. (2012) A peroxidase-dependent apoplastic oxidative burst in cultured Arabidopsis cells functions in MAMP-elicited defense. Plant Physiol 158:2013-27|
|Whiteman, Noah K; Groen, Simon C; Chevasco, Daniela et al. (2011) Mining the plant-herbivore interface with a leafmining Drosophila of Arabidopsis. Mol Ecol 20:995-1014|
|Gopalan, Suresh; Ausubel, Frederick M (2011) A high throughput amenable Arabidopsis-P. aeruginosa system reveals a rewired regulatory module and the utility to identify potent anti-infectives. PLoS One 6:e16381|
|Adio, Adewale M; Casteel, Clare L; De Vos, Martin et al. (2011) Biosynthesis and defensive function of Nýý-acetylornithine, a jasmonate-induced Arabidopsis metabolite. Plant Cell 23:3303-18|
|Yao, Youli; Danna, Cristian H; Zemp, Franz J et al. (2011) UV-C-irradiated Arabidopsis and tobacco emit volatiles that trigger genomic instability in neighboring plants. Plant Cell 23:3842-52|
|Danna, Cristian H; Millet, Yves A; Koller, Teresa et al. (2011) The Arabidopsis flagellin receptor FLS2 mediates the perception of Xanthomonas Ax21 secreted peptides. Proc Natl Acad Sci U S A 108:9286-91|
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