AUTHOR=Pastor Victoria , Gamir Jordi , Camañes Gemma , Cerezo Miguel , Sánchez-Bel Paloma , Flors Victor 

TITLE=Disruption of the ammonium transporter AMT1.1 alters basal defenses generating resistance against Pseudomonas syringae and Plectosphaerella cucumerina

JOURNAL=Frontiers in Plant Science

VOLUME=5

YEAR=2014

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2014.00231

DOI=10.3389/fpls.2014.00231

ISSN=1664-462X

ABSTRACT=<p>Disruption of the high-affinity nitrate transporter <italic>NRT2.1</italic> activates the priming defense against <italic>Pseudomonas syringae</italic>, resulting in enhanced resistance. In this study, it is demonstrated that the high-affinity ammonium transporter <italic>AMT1.1</italic> is a negative regulator of <italic>Arabidopsis</italic> defense responses. The T-DNA knockout mutant <italic>amt1.1</italic> displays enhanced resistance against <italic>Plectosphaerella cucumerina</italic> and reduced susceptibility to <italic>P. syringae</italic>. The impairment of <italic>AMT1.1</italic> induces significant metabolic changes in the absence of challenge, suggesting that <italic>amt1.1</italic> retains constitutive defense responses. Interestingly, <italic>amt1.1</italic> combats pathogens differently depending on the lifestyle of the pathogen. In addition, N starvation enhances the susceptibility of wild type plants and the mutant <italic>amt1.1</italic> to <italic>P. syringae</italic> whereas it has no effect on <italic>P. cucumerina</italic> resistance. The metabolic changes of <italic>amt1.1</italic> against <italic>P. syringae</italic> are subtler and are restricted to the phenylpropanoid pathway, which correlates with its reduced susceptibility. By contrast, the <italic>amt1.1</italic> mutant responds by activating higher levels of camalexin and callose against <italic>P. cucumerina</italic>. In addition, <italic>amt1.1</italic> shows altered levels of aliphatic and indolic glucosinolates and other Trp-related compounds following infection by the necrotroph. These observations indicate that <italic>AMT1.1</italic> may play additional roles that affect N uptake and plant immune responses.</p>