Fig 1.
Microbial effectors dephosphorylate inositol phosphates to promote disease.
A) The bacterial pathogen Xanthomonas uses a syringe-like injection system, known as the type III secretion system (T3SS), to deliver the effector XopH or orthologs as AvrBs7 into host cells. XopH dephosphorylates InsP6 (phytate) at the C1 position, classifying it as a 1-phytase. The released phosphate could increase intracellular and apoplastic phosphate (Pi) levels, potentially promoting Xanthomonas growth in planta. CW (cell wall), PM (plasmamembrane), CY (cytoplasm), AP (apoplast). B) The fungal pathogen Magnaporthe translocates MoNUDIX effectors into host cells, where they dephosphorylate inositol pyrophosphates (PP-InsPs). This dephosphorylation releases the transcription factor PHR from repressive SPX–PHR complexes, thereby activating the phosphate starvation response (PSR). The PSR is thought to promote microbial infection by suppressing plant immunity, enhancing phosphate availability for the pathogen, or both. BIC (biotrophic interfacial complexes).