Transcriptome-derived networks reconstruct distinct immune strategies to counteract fungal infection under different iron availability between Arabidopsis and rice

Fe, an essential element for plants to sustain central biological functions, recently emerged as a modulator of immunity. However, our understanding of the crosstalk between Fe and defence is limited. Here, we report antagonistic immune phenotypes in Arabidopsis thaliana and Oryza sativa infected by Colletotrichum higginsianum and Magnaporthe oryzae under different Fe nutritional status. Functional and topological analysis of transcriptional networks unveiled differences in complexity and hierarchy for similar biological functions, as well as in Fe usage and distribution, between the two pathosystems, with a focus on the plant side. Mechanistically, our results are consistent with a regulatory role of Fe in the biosynthesis of the defensive metabolites glucosinolates in A. thaliana (joint effect hypothesis), whereas O. sativa uses Fe to trigger oxidative stress at infection sites (metal defence). Nevertheless, common regulatory features might differently coordinate the transcriptome responses of both species. An evolutionary interpretation of divergences in the interplay between Fe and plant immunity is discussed.