Arabidopsis ribosomal RNA processing meerling mutants exhibit suspensor-derived polyembryony due to direct reprogramming of the suspensor

we report a novel mutant called meerling-1 (mrl-1), which shows a high penetrance of suspensor derived polyembryony. In mrl-1, ectopic embryos develop upon delayed development of the embryo proper. Eventually, embryos from both lineages successfully develop into normal plants and complete their life cycle. We identified the causal mutation as a genomic rearrangement altering the promoter of the Arabidopsis UTP18 homolog that encodes a nucleolar localized WD40-repeat protein involved in processing 18S pre-ribosomal RNA.