Catalytic subunit of protein phosphatase 6 (PP6) (Probable). Dephosphorylates phosphorylated phytochromes, with a preference toward Pfr forms (PubMed:12468726). Plays a major role in the photoperiodic control of flowering time in long days by modulating phytochrome signals in flowering time control (PubMed:12468726). 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 protein (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 (PubMed:12468726). Interacts with TAP46 (PubMed:24357600, PubMed:12468726). Interacts with NRP (PubMed:24357600). 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). Early flowering (PubMed:12468726). 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 (PubMed:22715043). Belongs to the PPP phosphatase family. PP-6 (PP-V) subfamily.