| Summary: | <p>Abstract</p> <p>Background</p> <p>Within the scanning model of translation initiation, reinitiation is a non-canonical mechanism that operates on mRNAs harboring upstream open reading frames. The h subunit of eukaryotic initiation factor 3 (eIF3) boosts translation reinitiation on the uORF-containing mRNA coding for the Arabidopsis bZip transcription factor, AtbZip11, among others. The RPL24B protein of the large ribosomal subunit, which is encoded by <it>SHORT VALVE1</it>, likewise fosters translation of uORF-containing mRNAs, for example mRNAs for auxin response transcription factors (ARFs).</p> <p>Results</p> <p>Here we tested the hypothesis that RPL24B and eIF3h affect translation reinitiation in a similar fashion. First, like <it>eif3h </it>mutants, <it>rpl24b </it>mutants under-translate the AtbZip11 mRNA, and the detailed spectrum of translational defects in <it>rpl24b </it>is remarkably similar to that of <it>eif3h</it>. Second, <it>eif3h </it>mutants display defects in auxin mediated organogenesis and gene expression, similar to <it>rpl24b</it>. Like AtbZip11, the uORF-containing ARF mRNAs are indeed undertranslated in <it>eif3h </it>mutant seedlings.</p> <p>Conclusion</p> <p>We conclude that, similar to eIF3h, RPL24B bolsters the reinitiation competence of uORF-translating ribosomes. Coordination between eIF3 and the large ribosomal subunit helps to fine-tune translation of uORF-containing mRNAs and, in turn, to orchestrate plant development.</p>
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