AUTHOR=Kuhn Hannah , Lorek Justine , Kwaaitaal Mark , Consonni Chiara , Becker Katia , Micali Cristina , Ver Loren van Themaat Emiel , Bednarek Paweł , Raaymakers Tom M. , Appiano Michela , Bai Yuling , Meldau Dorothea , Baum Stephani , Conrath Uwe , Feussner Ivo , Panstruga Ralph 

TITLE=Key Components of Different Plant Defense Pathways Are Dispensable for Powdery Mildew Resistance of the Arabidopsis mlo2 mlo6 mlo12 Triple Mutant

JOURNAL=Frontiers in Plant Science

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2017.01006

DOI=10.3389/fpls.2017.01006

ISSN=1664-462X

ABSTRACT=<p>Loss of function mutations of particular plant <italic>MILDEW RESISTANCE LOCUS O</italic> (<italic>MLO</italic>) genes confer durable and broad-spectrum penetration resistance against powdery mildew fungi. Here, we combined genetic, transcriptomic and metabolomic analyses to explore the defense mechanisms in the fully resistant <italic>Arabidopsis thaliana mlo2 mlo6 mlo12</italic> triple mutant. We found that this genotype unexpectedly overcomes the requirement for indolic antimicrobials and defense-related secretion, which are critical for incomplete resistance of <italic>mlo2</italic> single mutants. Comparative microarray-based transcriptome analysis of <italic>mlo2 mlo6 mlo12</italic> mutants and wild type plants upon <italic>Golovinomyces orontii</italic> inoculation revealed an increased and accelerated accumulation of many defense-related transcripts. Despite the biotrophic nature of the interaction, this included the non-canonical activation of a jasmonic acid/ethylene-dependent transcriptional program. In contrast to a non-adapted powdery mildew pathogen, the adapted powdery mildew fungus is able to defeat the accumulation of defense-relevant indolic metabolites in a MLO protein-dependent manner. We suggest that a broad and fast activation of immune responses in <italic>mlo2 mlo6 mlo12</italic> plants can compensate for the lack of single or few defense pathways. In addition, our results point to a role of Arabidopsis MLO2, MLO6, and MLO12 in enabling defense suppression during invasion by adapted powdery mildew fungi.</p>