Phosphate-induced resistance to pathogen infection in Arabidopsis

In nature, plants are concurrently exposed to a number of abiotic and biotic stresses. Our understanding of convergence points between responses to combined biotic/abiotic stress pathways remains, however, rudimentary. Here we show that MIR399 overexpression, loss-of-function of PHOSPHATE2 (PHO2), or treatment with high phosphate (Pi) levels is accompanied by an increase in Pi content and accumulation of reactive oxygen species (ROS) in Arabidopsis thaliana. High Pi plants (e.g., miR399 overexpressors, pho2 mutants, and plants grown under high Pi supply) exhibited resistance to infection by necrotrophic and hemibiotrophic fungal pathogens. In the absence of pathogen infection, the expression levels of genes in the salicylic acid (SA)- and jasmonic acid (JA)-dependent signaling pathways were higher in high Pi plants compared to wild-type plants grown under control conditions, which is consistent with increased levels of SA and JA in non-infected high Pi plants. During infection, an opposite regulation in the two branches of the JA pathway (ERF1/PDF1.2 and MYC2/VSP2) occurs in high Pi plants. Thus, while pathogen infection induces PDF1.2 expression in miR399 OE and pho2 plants, VSP2 expression is downregulated by pathogen infection in these plants. This study supports the notion that Pi accumulation promotes resistance to infection by fungal pathogens in Arabidopsis, while providing a basis to better understand interactions between Pi signaling and hormonal signaling pathways for modulation of plant immune responses.

We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI).

This research was supported by the Ministry of Science, Innovation and Universities/FEDER/Innovation-State Research Agency (AEI) (grant RTI2018-101275-B-I00) to BSS, the Research Promotion Plan from the Universitat Jaume I (UJI-B2019-2), and the Scientific Instrumentation Central Service from the Universitat Jaume I to VF. We acknowledge financial support from the Spanish Ministry of Science/AEI through the “Severo Ochoa Programme for Centres of Excellence in R&D” SEV-2015-0533 and CEX2019-000902-S, and the CERCA Programme/“Generalitat de Catalunya”. BVT was a recipient of a fellowship from the Ministry of Economy, Industry and Competitiveness/AEI (BES-2016-076289). MBP was a recipient of a scholarship from La Caixa Foundation.

Peer reviewed