Do PFT1 and HY5 interact in regulation of sulfate assimilation by light in Arabidopsis?

• We show that PFT1 may play a role in light regulation of APS reductase.
• PFT1 affects transcript levels of APS reductase in an isoform specific way as activator and repressor.
• Light regulation of APS reductase seems to require a complex interplay of PFT1 and HY5.

Sulfate assimilation pathway is highly responsive to changes in environment, but the mechanisms of such regulation are only slowly beginning to unravel. Here we show evidence that PHYTOCHROME AND FLOWERING TIME 1 (PFT1) may be another component of the sulfate assimilation regulatory circuit. Transcriptional regulation by light of the key enzyme of sulfate assimilation, adenosine 5′phosphosulfate (APS) reductase, is disturbed in pft1-2 mutants. PFT1, however, affects also APS reductase enzyme activity, flux through the sulfate assimilation pathway and accumulation of glutathione. In addition, our data suggest a possible interplay of PFT1 with another transcription factor, HY5, in regulation of APS reductase by light.