Transcriptional regulator that acts as a repressor of the gibberellin (GA) signaling pathway. Transcription coactivator of the zinc finger transcription factors GAF1/IDD2 and ENY/IDD1 in regulation of gibberellin homeostasis and signaling (PubMed:25035403). No effect of the BOI proteins on its stability. Probably acts by participating in large multiprotein complexes that repress transcription of GA-inducible genes. Positively regulates XERICO expression. In contrast to RGA, it is less sensitive to GA. Its activity is probably regulated by other phytohormones such as auxin and ethylene. Involved in the regulation of seed dormancy and germination, including glucose-induced delay of seed germination (PubMed:24989044). Involved in the process leading to microtubules (MTs) dissociation in response to gibberellic acid (GA) probably by mediating the translocation of the prefoldin co-chaperone complex from the cytoplasm to the nucleus (PubMed:23583555). Transcription activation is repressed by gibberellic acid GA(3) in the presence of TPR4. Interacts directly with the GID2/SLY1 component of the SCF(GID2) complex. Interacts (via N-terminus) with GID1A, GID1B and GID1B (via N-terminus). Interacts with the BOI proteins BOI, BRG1, BRG2, BRG3 and NUP58 (PubMed:15155881, PubMed:15161962, PubMed:15173565, PubMed:16709201, PubMed:19037309, PubMed:23482857, PubMed:23840761). Interacts with TOPP4 (PubMed:25010794, PubMed:15155881, PubMed:15161962, PubMed:15173565, PubMed:16709201, PubMed:19037309, PubMed:23482857, PubMed:23840761). Interacts with TCP14 and TCP15 (PubMed:25655823). Interacts with FLZ5 (Ref.27). Binds to and coactivates GAF1/IDD2 and ENY/IDD1 at the promoter of GA20OX2 gene (PubMed:25035403). Binds to PDF2 and ATML1 (PubMed:24989044). Interacts with the prefoldin alpha subunits PFD3 and PFD5 in the nucleus (PubMed:23583555). Ubiquitously expressed. Expressed in rosette leaves, roots, stems and inflorescences of greenhouse grown. Upon seed imbibition, increased GA levels in the epidermis reduce DELLA proteins (e.g. GAI/RGA2, RGA/RGA1/GRS and RGL2/SCL19) abundance and release, in turn, ATML1 and PDF2 which activate LIP1 expression, thus enhancing germination potential. Phosphorylated. Gibberellin (GA) induces dephosphorylation of GAI by TOPP4 and subsequent degradation by the proteasomal pathway. May be ubiquitinated, as suggested by its interaction with GID2. Ubiquitination is however unsure since in contrast to other DELLA proteins, it is not ubiquitinated and degraded upon GA application. Nevertheless, ubiquitination may be triggered by other processes. Rga, gai, rgl1, rgl2 and rgl3 pentuple mutant displays constitutive GA responses even in the absence of GA treatment. Belongs to the GRAS family. DELLA subfamily.