Figure 10.

Schematic Illustration of PAP Metabolism and Transport.

(1) PAPST1 is the major transporter that delivers newly synthesized PAPS from the plastid to the cytosol.

(2) In the cytosol and the Golgi apparatus, PAPS consumption via sulfotransferases results in PAP release.

(3) PAPST2 is the major transporter that imports cytosolic PAP into mitochondria and plastids, where it becomes degraded via FRY1.

(4) The concerted interaction between PAP production, transport, and degradation prevents cytosolic PAP accumulation (marked in red), the associated nuclear responses, and phenotypic symptoms.