AUTHOR=Wynn April N., Seaman Andrew A., Jones Ashley L., Franks Robert G.

TITLE=Novel functional roles for PERIANTHIA and SEUSS during floral organ identity specification, floral meristem termination, and gynoecial development

JOURNAL=Frontiers in Plant Science

VOLUME=5

YEAR=2014

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2014.00130

DOI=10.3389/fpls.2014.00130

ISSN=1664-462X

ABSTRACT=<p>The gynoecium is the female reproductive structure of angiosperm flowers. In <italic>Arabidopsis thaliana</italic> the gynoecium is composed of two carpels that are fused into a tube-like structure. As the gynoecial primordium arises from the floral meristem, a specialized meristematic structure, the carpel margin meristem (CMM), develops from portions of the medial gynoecial domain. The CMM is critical for reproductive competence because it gives rise to the ovules, the precursors of the seeds. Here we report a functional role for the transcription factor <italic>PERIANTHIA</italic> (<italic>PAN</italic>) in the development of the gynoecial medial domain and the formation of ovule primordia. This function of <italic>PAN</italic> is revealed in <italic>pan aintegumenta (ant)</italic> as well as <italic>seuss (seu) pan</italic> double mutants that form reduced numbers of ovules. Previously, <italic>PAN</italic> was identified as a regulator of perianth organ number and as a direct activator of <italic>AGAMOUS (AG)</italic> expression in floral whorl four. However, the <italic>seu pan</italic> double mutants display enhanced ectopic <italic>AG</italic> expression in developing sepals and the partial transformation of sepals to petals indicating a novel role for <italic>PAN</italic> in the repression of <italic>AG</italic> in floral whorl one. These results indicate that <italic>PAN</italic> functions as an activator or repressor of <italic>AG</italic> expression in a whorl-specific fashion. The <italic>seu pan</italic> double mutants also display enhanced floral indeterminacy, resulting in the formation of “fifth whorl” structures and disruption of <italic>WUSCHEL</italic> (<italic>WUS</italic>) expression patterns revealing a novel role for <italic>SEU</italic> in floral meristem termination.</p>