Phosphate –defense balance

Role of inositol polyphosphates (InsPs) InsP6, InsP7 and InsP8 in maintaining the phosphate homeostasis is increasingly being established. Additionally, it is reported that phosphate uptake is accompanied by suppression of immune responses to aid colonization of Pi-remobilizing bacteria. Here, we show that Arabidopsis thaliana InsP-kinases IPK1, ITPK1 and VIH2 in addition to maintaining phosphate homeostasis, also negatively regulate Salicylic acid (SA)-dependent immunity. In mutants of above InsP-kinases, up regulated SA-signaling sectors potentiate several phosphate-starvation inducible (PSI) genes which in turn reciprocally moderate expression of defense-related markers. Similar to the observation in the above mutants, upon pathogen challenge the induction of SA increase the phosphate uptake from the soil and SA-dependent up-regulation of immunity is partially dependent on phosphate regulatory genes PHR1/PHL1. On the contrary, under phosphate-deprived conditions the up regulated SA is diverted to promote the expression of SA inducible PSI- genes and immunity is suppressed possibly involving the role of negative immune regulators. Plant Cell Reports. https://doi.org/10.1007/s00299-021-02812-3.