PHOSPHATE TRANSPORTER 5 modulates PHR1-dependent immunity by regulating the status of intracellular inositol pyrophosphates

The Pi transporters at vacuolar membranes (tonoplast) play critical roles in buffering the cytosolic Pi level against fluctuations of external Pi and metabolic activities. We and others have identified the SPX-MFS proteins, which contain an N-terminal SPX domain and a C-terminal major facilitator superfamily (designated as PHT5 Pi transporter family or VPT), as vacuolar Pi influx transporters and demonstrated their essential role in vacuolar Pi storage and the maintenance of cytosolic Pi homeostasis. To understand the global impact of defective vacuolar Pi storage/buffering, we performed a transcriptomic analysis of the pht5-tri Arabidopsis mutant and Col-0 wild-type (WT) plants. We observed the enrichment of many defense-related GO terms among 2795 differentially expressed genes between Col-0 wild-type (WT) plants and pht5-tri mutant.