Apoplast Metabolomics Profiling Reveals Nitrogen-Dependent Modulation of Plant-Pathogen Interactions

Area of Science:

• Plant pathology
• Plant-microbe interactions
• Biotic and abiotic stress crosstalk

Background:

• Nitrogen (N) limitation is known to increase pathogen loads and virulence factor expression in plants.
• The apoplast, a key interface for plant-pathogen interactions, plays a crucial role in mediating these responses.

Purpose of the Study:

• To investigate the role of the apoplast in the crosstalk between nitrogen limitation and infection by the apoplastic bacterium Erwinia amylovora in Arabidopsis thaliana.
• To determine how apoplastic fluid composition under varying nitrogen conditions affects bacterial virulence.

Main Methods:

• Extraction and in vitro application of apoplast wash fluids (AWF) from plants grown under low N (LN) and high N (HN) conditions.
• Metabolomic analysis of AWF to identify differences in metabolite profiles.
• Assessing the impact of AWF and individual metabolites on Erwinia amylovora virulence gene expression.

Main Results:

• LN-AWF significantly induced stronger bacterial virulence gene expression compared to HN-AWF.
• Metabolomic analysis revealed distinct proportions of common metabolites in LN-AWF versus HN-AWF, directly linked to N availability.
• Bacterial infection altered apoplast metabolite proportions in plants under LN conditions.
• Out of 43 tested metabolites, 29 activated and 2 (GABA, citrate) repressed bacterial virulence gene expression.

Conclusions:

• Nitrogen availability directly impacts apoplastic content and influences plant-pathogen interactions.
• Altered apoplastic metabolite profiles under nitrogen-limiting conditions promote pathogen virulence.
• The apoplast acts as a critical signaling hub mediating the effects of abiotic stress on biotic interactions.