An autoregulatory mechanism modulates translation of heterologous proteins in tobacco chloroplast

Chloroplasts, due to their endosymbiotic origin, are organelles with both nuclear-encoded and chloroplast-encoded proteins, thus a highly integrated modulation between the nucleus and the plastome is needed in plant cell development. This coordinate expression in chloroplasts takes place mainly through translational regulation, which is a major feature of plastome gene expression. Although translational autoregulation mechanisms in algae have been described for subunits of heteromeric proteins and termed control by epistasy of synthesis (CES), in plant chloroplasts only few autoregolatory proteins have been identified. Here we report the existence of a self-regulation mechanism triggered by a soluble recombinant protein (phaseolin) accumulation in the stroma of chloroplast-transformed plants, revealing that autoregulation of translation in the chloroplast is not only limited to subunits of heteromeric proteins.