Endosomal sorting complex required for transport (ESCRT) component regulating multivesicular body (MVB) protein sorting and plant growth (PubMed:25438943). Required for the formation of intra-luminal vesicles (ILVs)in MVBs (PubMed:25438943). Binds to phosphatidylinositol-3-phosphate (PI3P) and ubiquitin (PubMed:24843126, PubMed:25438943). Controls IRT1 recycling to the plasma membrane and impacts the polar delivery of this transporter to the outer plasma membrane domain (PubMed:24843126). Regulates ubiquitin-dependent membrane protein degradation, vacuolar transport, autophagy, and vacuole biogenesis (PubMed:25624505, PubMed:25699591). ESCRT component that binds ubiquitin and regulates vacuolar sorting of proteins (PubMed:27495812). Attenuates abscisic acid (ABA) signaling through RSL1-triggered degradation of the ABA receptors PYR1 and PYL4 (PubMed:27495812). Interacts with PYL4 and PYR1, and delivers the ubiquitinated ABA receptors as cargo to the vacuolar degradation pathway (PubMed:27495812). In response to ABA, is phosphorylated by SnRK2 kinases which mediate FREE1 nuclear import (PubMed:30962512). In the nucleus, interacts with the ABA-responsive transcription factors ABF4 and ABI5 to reduce their ability to bind to their cis-regulatory sequences of downstream genes, thus leading to transcriptional inhibition of ABA signaling pathway (PubMed:30962512). Negatively regulates salt stress tolerance via a negative feedback loop involving ABA signaling pathway (PubMed:32540007). Part of the ESCRT-I complex (PubMed:25438943). Interacts with VPS23A and VPS23B, but not with VPS28 or VPS37 (PubMed:25438943). Interacts with IRT1 (PubMed:24843126). Interacts with SH3P2 (PubMed:25699591, PubMed:25624505). Interacts with SH3P3, but not with SH3P1 (PubMed:25699591). Interacts (via N-terminus) with PYL4 and PYR3 (PubMed:27495812). Interacts (via C-terminus) with SNRK2D/SNRK2.2, SNRK2I/SNRK2.3, ABF4 and ABI5 (PubMed:30962512). Interacts with SINAT1, SINAT2, SINAT3 and SINAT4 (PubMed:32786047, PubMed:32753431). Interacts with SINAT5 (PubMed:32786047). Component of a phosphoinositide 3-kinase (PI3K) complex containing ATG6, SH3P2 and FREE1 (PubMed:25624505). In response to abscisic acid (ABA), SnRK2 kinases phosphorylate FREE1, a step requisite for ABA-induced FREE1 nuclear import. Ubiquitous. Lowest expression in mature seeds. Not regulated by iron starvation (PubMed:24843126). Induced by abscisic acid (ABA), salt stress and osmotic stress (PubMed:32540007). The FYVE domain is required for PI3P binding (PubMed:25438943). The N-terminal domain (31-86) is required for the interaction with VPS23A and B (PubMed:25438943). The C-terminal domain (515-601) is required for the binding to ubiquitin (PubMed:25438943). The C-terminal coiled-coil region is required for the interaction with SH3P2 (PubMed:25624505). Phosphorylated at Ser-530 and Ser-533 by SNRK2D/SNRK2.2 and SNRK2I/SNRK2.3 in response to abscisic acid (ABA) (PubMed:30962512). Phosphorylation is necessary for ABA-induced FREE1 nuclear import (PubMed:30962512). Ubiquitinated by SINAT1, SINAT2, SINAT3 and SINAT4 for subsequent proteasomal degradation. Seedling lethality when homozygous (PubMed:25438943, PubMed:25699591). Degenerated root surface structures and vacuoles with altered morphology (PubMed:25699591). Accumulation of ubiquitinated membrane-associated proteins (PubMed:25699591). Hypersensitivity to abscisic acid (ABA) due to impaired targeting of ABA receptors (e.g. PYL4 and PYR1) for vacuolar degradation, thus leading to their accumulation and an enhanced response to ABA (PubMed:27495812). Reduction-of-function FREE1 alleles exhibit enhanced sensitivity to abscisic acid-mediated inhibition of seedling establishment (PubMed:27495812). Seedlings overexpressing FREE1 exhibit increased sensitivity to salt stress (PubMed:32540007). The predicted gene At1g20110 has been split into 2 genes: At1g20110 and At1g20120.