Plastid translation as a developmental checkpoint? Plastid ribosomal protein EMB27 is required for maize embryogenesis

Plant embryos undergo crucial development in order to establish themselves for photosynthesis.It begins at the early stages of embryogenesis with the formation of plastids in specific cells during tissue patterning (West and Harada, 1993).Genetic screens in Arabidopsis and maize have revealed embryo lethality in numerous chloroplast-defective mutants (Meinke, 2020).However, the observed phenotypic variations across different species and genetic backgrounds complicate our understanding of the relationship between these two defects.(Parker et al., 2014).Therefore, how chloroplast biogenesis influences plant embryogenesis remains unresolved.In this issue of Plant Physiology, Liu et al. ( 2024) explore the role of EMB27, a plastid ribosomal protein S13 (RPS13), in maize development.Through genetic experiments and biochemical assays, the authors provide evidence that EMB27 is involved in plastid protein translation, required in both plastid and embryo development in maize (Fig. 1A).The functional analysis of EMB27 offers some insights into the yet-to-be-resolved link between chloroplast biogenesis and plant embryogenesis.The investigation started with the isolation of the embryo defective27-1 (emb27-1) mutant from a transposon insertion population.A mature maize kernel is composed of an embryo that includes a scutellum, which resembles a shield-like cotyledon, all of which are enclosed within the pericarp alongside the persistent endosperm (Fig. 1A).emb27-1 exhibits a premature arrest in embryo development although the development of the endosperm remains unaffected (Fig. 1B).EMB27-1 encodes a highly conserved RPS13, a key component of the small subunit of the plastid ribosome.Interestingly, the authors identified a weaker allele, emb27-2, exhibiting normal embryo development but displaying albinism and seedling lethality due to its inability to