<i>KLU</i> suppresses megasporocyte cell fate through SWR1-mediated activation of <i>WRKY28</i> expression in <i>Arabidopsis</i>

Abstract

Germ-line specification is essential for sexual reproduction. In the ovules of most flowering plants, only a single hypodermal cell enlarges and differentiates into a megaspore mother cell (MMC), the founder cell of the female germ-line lineage. The molecular mechanisms restricting MMC specification to a single cell remain elusive. We show that the <i>Arabidopsis</i> transcription factor <i>WRKY28</i> is exclusively expressed in hypodermal somatic cells surrounding the MMC and is required to repress these cells from acquiring MMC-like cell identity. In this process, the SWR1 chromatin remodeling complex mediates the incorporation of the histone variant H2A.Z at the <i>WRKY28</i> locus. Moreover, the cytochrome P450 gene <i>KLU</i>, expressed in inner integument primordia, non-cell-autonomously promotes <i>WRKY28</i> expression through H2A.Z deposition at <i>WRKY28.</i> Taken together, our findings show how somatic cells in ovule primordia cooperatively use chromatin remodeling to restrict germ-line cell specification to a single cell.