Ribosomal composition and control of leaf development

Protein synthesis in plants occurs at three sub-cellular locations that have their own specific ribosomal compositions: the cytoplasm, mitochondria and plastids. An increased demand for functional and efficient translational machinery is required during development of leaves. The role of specific ribosomal protein (RP-) encoding genes in the regulation of development has been underestimated as housekeeping. However, in Arabidopsis thaliana several RP loss-of-function mutations have been identified that affect cell division or cell expansion and consequently result in deformed leaf size and shape, indicating cell- or development-specific roles of RPs during leaf growth. This view is strengthened by the observation that the expression of many RP genes follows distinct patterns during leaf development. Moreover, translatomics data demonstrate that ribosomal composition is dynamic and organized in a spatio-temporal manner. The regulation of RP gene transcription via different promoter-localized cis-elements allows additional control relevant for leaf growth. We conclude that RPs have a more distinct role in regulating specific processes in leaf development than previously anticipated, and envisage fascinating novel insights in the near future.