Abstract
The carbon/nitrogen (C/N) balance of plants is not only required for growth and development but also plays an important role in basal immunity. However, the mechanisms that link C/N regulation and basal immunity are poorly understood. We previously demonstrated that the Arabidopsis (Arabidopsis thaliana) Arabidopsis Tóxicos en Levadura31 (ATL31) ubiquitin ligase, a regulator of the C/N response, positively regulates the defense response against bacterial pathogens. In this study, we identified the plasma membrane-localized soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptor SYNTAXIN OF PLANTS121 (SYP121) as a novel ATL31 interactor. The syp121-1 loss-of-function mutant showed similar hypersensitivity to C/N stress conditions as the atl31 atl6 double mutant. SYP121 is essential for resistance to penetration by powdery mildew fungus and positively regulates the formation of cell wall appositions (papillae) at fungal entry sites. Microscopic analysis demonstrated that ATL31 was specifically localized around papillae. In addition, ATL31 overexpressors showed accelerated papilla formation, enhancing their resistance to penetration by powdery mildew fungus. Together, these data indicate that ATL31 plays an important role in connecting the C/N response with basal immunity by promoting papilla formation through its association with SYP121.
Highlights
The carbon/nitrogen (C/N) balance of plants is required for growth and development and plays an important role in basal immunity
Assessment of the SNARE complex consisting of SYNTAXIN OF PLANTS121 (SYP121), SOLIBLE N-ETHYLMALEIMIDESENSITIVE FACTOR ADAPTOR PROTEIN33 (SNAP33), and VESICLE-ASSOCIATED MEMBRANE PROTEIN721 (VAMP721)/VAMP722 showed that transcription of the genes encoding all of these proteins, except for VAMP721, was highly positively correlated with the transcription of Arabidopsis Tóxicos en Levadura31 (ATL31) and ATL6
Since we previously found that plasma membrane-localized ATL31 played a role in basal immunity against bacterial pathogens (Maekawa et al, 2012), we examined the effects of the relationship between ATL31 and SYP121 on basal immunity against fungal pathogens
Summary
The carbon/nitrogen (C/N) balance of plants is required for growth and development and plays an important role in basal immunity. ATL31 overexpressors showed accelerated papilla formation, enhancing their resistance to penetration by powdery mildew fungus. Together, these data indicate that ATL31 plays an important role in connecting the C/N response with basal immunity by promoting papilla formation through its association with SYP121. Powdery mildews are among the most important diseases of food and ornamental plants, with a high annual global economic impact (for review, see Glawe, 2008; Micali et al, 2008). These fungal species rely on living host plant tissues for survival, with many of these fungal species infecting a very narrow range of plant species. Arabidopsis (Arabidopsis thaliana) can resist Bgh penetration by the activation of basal immunity (Tucker and Talbot, 2001)
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