AUTHOR=Liu Simu , Bartnikas Lisa M. , Volko Sigrid M. , Ausubel Frederick M. , Tang Dingzhong 

TITLE=Mutation of the Glucosinolate Biosynthesis Enzyme Cytochrome P450 83A1 Monooxygenase Increases Camalexin Accumulation and Powdery Mildew Resistance

JOURNAL=Frontiers in Plant Science

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2016.00227

DOI=10.3389/fpls.2016.00227

ISSN=1664-462X

ABSTRACT=<p>Small secondary metabolites, including glucosinolates and the major phytoalexin camalexin, play important roles in immunity in <italic>Arabidopsis thaliana</italic>. We isolated an <italic>Arabidopsis</italic> mutant with increased resistance to the powdery mildew fungus <italic>Golovinomyces cichoracearum</italic> and identified a mutation in the gene encoding cytochrome P450 83A1 monooxygenase (CYP83A1), which functions in glucosinolate biosynthesis. The <italic>cyp83a1-3</italic> mutant exhibited enhanced defense responses to <italic>G. cichoracearum</italic> and double mutant analysis showed that this enhanced resistance requires NPR1, EDS1, and PAD4, but not SID2 or EDS5. In <italic>cyp83a1-3</italic> mutants, the expression of genes related to camalexin synthesis increased upon <italic>G. cichoracearum</italic> infection. Significantly, the <italic>cyp83a1-3</italic> mutant also accumulated higher levels of camalexin. Decreasing camalexin levels by mutation of the camalexin synthetase gene <italic>PAD3</italic> or the camalexin synthesis regulator <italic>AtWRKY33</italic> compromised the powdery mildew resistance in these mutants. Consistent with these observations, overexpression of <italic>PAD3</italic> increased camalexin levels and enhanced resistance to <italic>G. cichoracearum.</italic> Taken together, our data indicate that accumulation of higher levels of camalexin contributes to increased resistance to powdery mildew.</p>