Graduate Student University of Tennessee, Knoxville Knoxville, Tennessee
Body of Abstract: Organ initiation and patterning in plants requires coordinated cell-to-cell communication to control cell growth and differentiation. In Arabidopsis thaliana, multiple ovules initiate asynchronously along the elongating placentae from stage 9 to stage 10 of floral development. Previous research has established a role for the phytohormone auxin in governing the site of ovule initiation, and for CUP-SHAPED COTYLEDON (CUC) transcription factors in regulation of ovule spacing. ERECTA family receptor-like kinase signaling via the EPIDERMAL PATTERNING FACTOR-like 2 (EPFL2) secretory peptide ligand regulates ovule density and spacing during Arabidopsis fruit development, but the mechanisms underlying this regulation remain unclear. We further investigated the mechanism of ERECTA family signaling and EPFLs during ovule initiation in Arabidopsis. Our experiments established that EPFL1 and EPFL2 show unique, cell-type specific expression throughout the process of ovule initiation. These two ligands positively regulate ovule number in a partially redundant manner without significantly affecting placenta length. To characterize the mechanisms of this regulation, hormone signaling and expression of genes controlling ovule initiation were investigated in the epfl1 epfl2 mutant. Ultimately, this research further characterizes the mechanisms by which EPFL-mediated signaling positively regulates the initiation and spacing of ovules in Arabidopsis thaliana.