AUTHOR=Cruz Joelma O. , San Martin Juca A. B. , Lubini Greice , Strini Edward J. , Sobral Rómulo , Pinoti Vitor F. , Ferreira Pedro B. , Thomé Vanessa , Quiapim Andréa C. , Dornelas Marcelo C. , Pranchevicius Maria Cristina S. , Madueño Francisco , Costa M. Manuela R. , Goldman Maria Helena S. 

TITLE=SCI1 Is a Direct Target of AGAMOUS and WUSCHEL and Is Specifically Expressed in the Floral Meristematic Cells

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.642879

DOI=10.3389/fpls.2021.642879

ISSN=1664-462X

ABSTRACT=<p>The specified floral meristem will develop a pre-established number of floral organs and, thus, terminate the floral meristematic cells. The floral meristematic pool of cells is controlled, among some others, by WUSCHEL (WUS) and AGAMOUS (AG) transcription factors (TFs). Here, we demonstrate that the <italic>SCI1</italic> (<italic><underline>S</underline>tigma/style <underline>c</underline>ell-cycle <underline>i</underline>nhibitor 1</italic>) gene, a cell proliferation regulator, starts to be expressed since the floral meristem specification of <italic>Nicotiana tabacum</italic> and is expressed in all floral meristematic cells. Its expression is higher in the floral meristem and the organs being specified, and then it decreases from outside to inside whorls when the organs are differentiating. <italic>SCI1</italic> is co-expressed with <italic>N. tabacum WUSCHEL</italic> (<italic>NtWUS</italic>) in the floral meristem and the whorl primordia at very early developmental stages. Later in development, <italic>SCI1</italic> is co-expressed with <italic>NAG1</italic> (<italic>N. tabacum AG</italic>) in the floral meristem and specialized tissues of the pistil. <italic>In silico</italic> analyses identified <italic>cis</italic>-regulatory elements for these TFs in the <italic>SCI1</italic> genomic sequence. Yeast one-hybrid and electrophoresis mobility shift assay demonstrated that both TFs interact with the <italic>SCI1</italic> promoter sequence. Additionally, the luciferase activity assay showed that NAG1 clearly activates <italic>SCI1</italic> expression, while NtWUS could not do so. Taken together, our results suggest that during floral development, the spatiotemporal regulation of <italic>SCI1</italic> by NtWUS and NAG1 may result in the maintenance or termination of proliferative cells in the floral meristem, respectively.</p>