Catalytic subunit of protein phosphatase 6 (PP6) (Probable). Dephosphorylates phosphorylated phytochromes, with a preference toward Pfr forms. Plays a major role in the photoperiodic control of flowering time in long days by modulating phytochrome signals in flowering time control (By similarity). Involved in the regulation of polar auxin transport in roots (PubMed:22715043). Dephosphorylates directly the auxin efflux carriers PIN1 and PIN2, thus promoting their proper polar localization in root cell plasma membrane (PubMed:22715043). Acts antagonistically with the protein kinase PID to regulate the reversible phosphorylation of PIN and polar targeting, subsequently impacting polar auxin transport and plant development (PubMed:22715043). Involved in the regulation of abscisic acid (ABA) signaling during seed germination and postgermination seedling growth (PubMed:23404889). Functions as negative regulator of ABA signaling through direct dephosphorylation and destabilization of ABI5 (PubMed:23404889). Acts antagonistically with the protein kinase SRK2E/SNRK2.6 to regulate ABI5 phosphorylation and ABA responses (PubMed:23404889). Involved in the regulation of phosphorylation status in hypocotyl phototropism (PubMed:30373470). Involved in the negative regulation of photomorphogenesis by controlling the stability and transcriptional activity of PIF3 and PIF4 proteins in the dark, via the regulation of their phosphorylation status (PubMed:31527236). H2O + O-phospho-L-seryl-[protein] = L-seryl-[protein] + phosphate H2O + O-phospho-L-threonyl-[protein] = L-threonyl-[protein] + phosphate Binds 2 zinc ions per subunit. Interacts with PHYA and PHYB, mostly when they are phosphorylated and in Pfr forms (By similarity). Interacts with TAP46 (PubMed:21216945, PubMed:24357600) (By similarity). Interacts with PIN1 and PIN2 (PubMed:22715043). Interacts with ABI5 (PubMed:23404889). Interacts with PIF3 and PIF4 (PubMed:31527236). Protein phosphatase 6 (PP6) holoenzyme is a heterotrimeric complex formed by the catalytic subunit FYPP, a SAPS domain-containing subunit (SAL) and a protein phosphatase 2A regulatory subunit A (PP2AA) (PubMed:22715043). Mostly expressed in flowers (PubMed:12468726). Also detected to a lower extent in stems and leaves (PubMed:12468726). Expressed in roots (PubMed:22715043). No visible phenotype under normal growth conditions, but the double mutant plants fypp1 and fypp3 exhibit severe developmental defects in roots and leaves, and show defective gravitropism. Belongs to the PPP phosphatase family. PP-6 (PP-V) subfamily.