Abstract
During seed germination, the transition from a quiescent metabolic state in a dry mature seed to a proliferative metabolic state in a vigorous seedling is crucial for plant propagation as well as for optimizing crop yield. This work provides a detailed description of the dynamics of protein synthesis during the time course of germination, demonstrating that mRNA translation is both sequential and selective during this process. The complete inhibition of the germination process in the presence of the translation inhibitor cycloheximide established that mRNA translation is critical for Arabidopsis seed germination. However, the dynamics of protein turnover and the selectivity of protein synthesis (mRNA translation) during Arabidopsis seed germination have not been addressed yet. Based on our detailed knowledge of the Arabidopsis seed proteome, we have deepened our understanding of seed mRNA translation during germination by combining two-dimensional gel-based proteomics with dynamic radiolabeled proteomics using a radiolabeled amino acid precursor, namely [(35)S]-methionine, in order to highlight de novo protein synthesis, stability, and turnover. Our data confirm that during early imbibition, the Arabidopsis translatome keeps reflecting an embryonic maturation program until a certain developmental checkpoint. Furthermore, by dividing the seed germination time lapse into discrete time windows, we highlight precise and specific patterns of protein synthesis. These data refine and deepen our knowledge of the three classical phases of seed germination based on seed water uptake during imbibition and reveal that selective mRNA translation is a key feature of seed germination. Beyond the quantitative control of translational activity, both the selectivity of mRNA translation and protein turnover appear as specific regulatory systems, critical for timing the molecular events leading to successful germination and seedling establishment.
Highlights
From ‡INRA, Jean-Pierre Bourgin Institute (IJPB, UMR1318 INRAAgroParisTech), Laboratory of Excellence “Saclay Plant Sciences” (LabEx SPS), F-78026 Versailles, France; §AgroParisTech, Chair of Plant Physiology, F-75231 Paris, France; ¶CNRS/Bayer CropScience Joint Laboratory (UMR5240), F-69263 Lyon, France
Trol of translational activity, both the selectivity of mRNA translation and protein turnover appear as specific regulatory systems, critical for timing the molecular events leading to successful germination and seedling establishment
From one polypeptidic sequence corresponding to a single Arabidopsis Gene Indexes (AGIs), many different 2DE protein spots were visualized
Summary
Phase II corresponds to a period during which the seed imbibition level remains constant or slowly increases This step occurs without visible morphological changes of the seed, it is characterized by germination-specific metabolism that prepares the seed for radicle protrusion and seedling growth. The present study highlights the dynamic regulation of protein translation and turnover during the time course of seed germination To this end, we employed a combined approach involving two-dimensional gel-based differential proteomics and dynamic radiolabeled proteomics. We employed a combined approach involving two-dimensional gel-based differential proteomics and dynamic radiolabeled proteomics The integration of these proteomic results with publicly available transcriptomic data [18] provides an original perspective on the contribution of dynamic protein turnover and selective mRNA translation in seed germination
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