AP2/ERF transcription factor RAP2.6 regulates early flowering in Arabidopsis thaliana by altering S -nitrosothiol levels and cytokinin responses

RAP2.6, an AP2/ERF transcription factor (TF), regulates plant stress responses; however, its role in floral transition remains unexplored. Here, we evaluated RAP2.6’s role in flowering and the associated transcriptional changes in Arabidopsis thaliana under long-day conditions. RAP2.6 -overexpressing line showed early flowering with fewer rosette leaves, whereas rap2.6-1 mutant flowered later, had more rosette leaves, and higher expression of the floral repressor FLOWERING LOCUS C ( FLC ). Early flowering in the overexpressing line was accompanied by transcriptional activation of the floral integrators GIGANTEA ( GI ), FLOWERING LOCUS T ( FT ), and COSTANS ( CO ), potentially through RAP2.6 interaction with GCC/DRE cis -regulatory elements. RAP2.6 -mediated floral transition depended on nitric oxide (NO), with flowering time largely varying based on NO bioactivity. RAP2.6 was found to be a downstream regulator of Arabidopsis S-NITROSOGLUTATHIONE REDUCTASE 1 ( GSNOR1 ) in controlling S-nitrosothiol (SNO) levels, flowering time, and silique formation. The NITRIC OXIDE-ASSOCIATED 1 ( NOA1 )-dependent reduction in NO levels abolished early flowering in 35S::RAP2.6 plants without affecting silique formation. Furthermore, enhanced cytokinin sensitivity and upregulation of cytokinin biosynthetic genes suggest cytokinin involvement in RAP2.6-mediated flowering. Together, these findings highlight the crucial role of RAP2.6 in regulating flowering time by integrating redox and hormonal signaling to coordinate reproductive development in A. thaliana .