75 Integrating Membrane Transport with Male Gametophyte ... - TAIR

273 The Cytochrome P450 Monooxygenase CYP71A13 is Required for Camalexin Synthesis in
Arabidopsis
Jane Glazebrook, Christopher Botanga
Department of Plant Biology, University of Minnesota
Camalexin, a phytoalexin produced by Arabidopsis, plays an important role in resistance to the necrotrophic fungal
pathogen Alternaria brassicicola. The biosynthetic pathway for camalexin biosynthesis is not completely understood.
Tryptophan is converted to indole acetal oxime by cytochromes P450 CYP79B2 and CYP79B3. A double cyp79B2
cyp79B3 mutant fails to produce camalexin, indicating that indole acetal oxime is a precursor to camalexin as well
as to indole glucosinolates. PAD3 encodes CYP71B15, and pad3 mutants also fail to produce camalexin. CYP79B15
presumably acts downstream from indole acetal oxime, as production of indole glucosinolates are unaffected by pad3
mutations. Here, we show that CYP71A13 is also required for camalexin synthesis. Plants with cyp71A13 mutations
produce greatly reduced amounts of camalexin after infection by either Pseudomonas syringae or Alternaria brassicicola.
Like pad3 mutants, cyp71A13 mutants show increased susceptiblity to Alternaria brassicicola, but not to Pseudomonas
syringae. The cyp79B2 cyp79B3 double mutant also shows these phenotypes. Like PAD3, CYP71A13 is expressed at
very low levels in uninfected plants, and is rapidly and strongly indluced in response to infection. PAD3 and CYP71A13
expression levels are strongly correlated. We conclude that CYP71A13 carries out a reaction in the camalexin biosynthetic
pathway, most likely acting downstram from production of indole acetal oxime.
274 Functional Genomics of Arabidopsis Defense Responses Against Pseudomonas syringae
Lin Wang, Jane Glazebrook
University of Minnesota, Department of Plant Biology
Plant defense against bacterial pathogens is a complex and sophisticated system under the control of numerous
genes. Understanding how these genes function and how signals are transduced in the disease signaling network will be
potentially beneficial for enhancing disease resistance in crop species. A relatively high-throughput method for studying
functions of genes that are involved in Arabidopsis defense responses against Pseudomonas syringae has been developed.
Genes that were significantly up-regulated after P. syringae infection were chosen as our candidates. Homozygous T-
DNA insertion mutants of these target genes were then studied to determine whether or not they have enhanced disease
susceptibility (eds) phenotypes. So far, mutants with defects in more than 10 candidate genes have been found to have
eds phenotypes. We are now characterizing the eds mutants using a custom microarray to determine whether or not they
have defects in defense signaling. The results of these experiments will be presented.