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The functions of approximately one-third of the proteins in the model plant Arabidopsis remain unknown. It is likely that some of the genes encoding these proteins are essential, and thus indispensable for the survival of the plant; furthermore, these genes would be included in the minimum viable set required for plant life. Evolutionarily conserved single copy genes in flowering plants are enriched in essential housekeeping functions. Building on this observation, we designed a reverse genetic screen that focuses on evolutionarily conserved single copy Arabidopsis genes of unknown function with predominant expression in meristematic cells. This approach identified a previously uncharacterized essential Arabidopsis gene, named as EARLY ABORTION 1 (EBO1). Mutation of the EBO1 locus disrupts gametophyte and/or early embryo development, resulting in defective ovule or seed development. A functional fluorescent EBO1 fusion protein was found to localize to the nucleus, and co-immunoprecipitation experiments detected an interaction between EBO1 and Nucleolar Protein 58 (NOP58) and proteins involved in RNA metabolism, chromatin modification, and transcription. The presented results open a new line of investigation into an evolutionarily conserved mechanism involved in the development of both male and female gametophytes as well as seeds.