SCI1 expression in Nicotiana tabacum floral meristems is regulated by the transcription factors WUSCHEL, AINTEGUMENTA- LIKE6 AND AGAMOUS

CRUZ,J.O; STRINI, E.J; THOMÉ, V; SAN MARTIN, J.A.B; FERREIRA, P.B; GOLDMAN, G.H; LUBINI,G; PINOTI, V.F; GOLDMAN, M.H.S

Águas de Lindóia

Congreso; 65th Brazilian Congress of Genetics; 2019

Sociedade Brasileira de Genética

We previously described a gene that controls cell proliferation in the stigma and style ofNicotiana tabacum (DePaoli et al, 2011), which was named SCI1 (Stigma/style Cell-cycleInhibitor 1). To establish the onset of SCI1 expression, in situ hybridization analyzes wereperformed at different flower developmental stages. The results demonstrated that SCI1starts its expression when the floral meristem is specified and it is highly expressed at theemerging floral organ primordia. Its expression decreases in the developing floral organs,remaining in the pistil, in regions in which cell divisions are still occurring (style, stigma andovules). Remarkably, SCI1 is expressed temporal and spatially in the same cells/tissues asthe transcription factors (TFs) NtWUSCHEL (NtWUS) and NAG1 (N. tabacum AGAMOUS),as confirmed experimentally by in situ hybridization of the latter 2 genes. SCI1 genomicregion (4455bp), containing 4 exons, 3 introns and ~2kb upstream promoter region wascloned and sequenced. Transgenic plants expressing SCI1prom::SCI1-GFP were producedand confirmed the expression previously observed by in situ hybridization, as well as thenuclear localization of the SCI1 protein. In silico analysis of the SCI1 genomic sequenceidentified putative cis-acting elements in SCI1 promoter for the binding of NtWUS (position-203 to -212) and NAG1 (position -267 to -285). Yeast one-hybrid (Y1H) experiments usinga fragment of 443bp, upstream of the initial ATG (+1) of SCI1 coding sequence, confirmedthe binding of NtWUS and NAG1 transcription factors to SCI1 promoter. Considering thatSCI1 is an inhibitor of cell proliferation, it may act as an effector of floral meristemdetermination, a hypothesis we are currently investigating. Taken together the spatial andtemporal overlap of SCI1, NtWUS and NAG1 expression, and the binding of these 2transcription factors to SCI1 promoter region, we propose that both TFs are responsible toactivate SCI1 expression in the floral meristem and in the dividing cells in the floral organprimordia.