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Translation reinitiation and development are compromised in similar ways by mutations in translation initiation factor eIF3h and the ribosomal protein RPL24.

Zhou F, Roy B, von Arnim AG - BMC Plant Biol. (2010)

Bottom Line: Like AtbZip11, the uORF-containing ARF mRNAs are indeed undertranslated in eif3h mutant seedlings.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Genome Science and Technology Program, The University of Tennessee, Knoxville, TN 37996, USA.

ABSTRACT

Background: 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 SHORT VALVE1, likewise fosters translation of uORF-containing mRNAs, for example mRNAs for auxin response transcription factors (ARFs).

Results: Here we tested the hypothesis that RPL24B and eIF3h affect translation reinitiation in a similar fashion. First, like eif3h mutants, rpl24b mutants under-translate the AtbZip11 mRNA, and the detailed spectrum of translational defects in rpl24b is remarkably similar to that of eif3h. Second, eif3h mutants display defects in auxin mediated organogenesis and gene expression, similar to rpl24b. Like AtbZip11, the uORF-containing ARF mRNAs are indeed undertranslated in eif3h mutant seedlings.

Conclusion: 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.

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eif3h phenotypes reminiscent of defects in auxin transport or response. (A) eif3h naked shoot. Compared to the canonical pins of the pin1 mutant (B), eif3h pins tended to bear scaly, rudimentary organs. (C) eif3h siliques show defects in carpel development, similar to those of rpl24b/stv1-1 or ett-2, an allele of ARF3. White arrowheads point to the last node carrying stamens and red arrowheads point to the basal end of the carpel valves. (D) Rare monocotyledon phenotype of eif3h seedlings, similar to that of mp, an allele of ARF5. (E) Cotyledons were cleared to reveal defects in vascular development. Similar defects as in eif3h can be seen in rpl24b/stv1-1 [21].
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Figure 3: eif3h phenotypes reminiscent of defects in auxin transport or response. (A) eif3h naked shoot. Compared to the canonical pins of the pin1 mutant (B), eif3h pins tended to bear scaly, rudimentary organs. (C) eif3h siliques show defects in carpel development, similar to those of rpl24b/stv1-1 or ett-2, an allele of ARF3. White arrowheads point to the last node carrying stamens and red arrowheads point to the basal end of the carpel valves. (D) Rare monocotyledon phenotype of eif3h seedlings, similar to that of mp, an allele of ARF5. (E) Cotyledons were cleared to reveal defects in vascular development. Similar defects as in eif3h can be seen in rpl24b/stv1-1 [21].

Mentions: The emerging hypothesis that RPL24B cooperates with eIF3h predicts that mutations in the two genes have overlapping developmental phenotypes. Instead of a functional inflorescence with leaves and flowers, eif3h mutant plants sometimes formed a pin-formed shoot, especially when shifted from short-day to long-day growth conditions (20%, n = 90) (Fig. 3A). Pin-formed shoots are characteristic of defects in auxin transport or response, for example the pin1 mutant (Fig. 3B[27]) and mutations in the auxin response transcription factor, MONOPTEROS (MP)/ARF5 [35]. These data suggest that eIF3h may boost translation of proteins needed for auxin transport or auxin response. In further support of auxin response defects, some eif3h mutant seedlings had only a single cotyledon or two cotyledons of unequal size, similar to the mp (arf5) mutant (Fig. 3D) and rpl24b/stv1 [21]. Auxin defects often reveal themselves by cul-de-sac vascular elements in the cotyledons, and such defects were readily observed in the eif3h mutant (Fig. 3E).


Translation reinitiation and development are compromised in similar ways by mutations in translation initiation factor eIF3h and the ribosomal protein RPL24.

Zhou F, Roy B, von Arnim AG - BMC Plant Biol. (2010)

eif3h phenotypes reminiscent of defects in auxin transport or response. (A) eif3h naked shoot. Compared to the canonical pins of the pin1 mutant (B), eif3h pins tended to bear scaly, rudimentary organs. (C) eif3h siliques show defects in carpel development, similar to those of rpl24b/stv1-1 or ett-2, an allele of ARF3. White arrowheads point to the last node carrying stamens and red arrowheads point to the basal end of the carpel valves. (D) Rare monocotyledon phenotype of eif3h seedlings, similar to that of mp, an allele of ARF5. (E) Cotyledons were cleared to reveal defects in vascular development. Similar defects as in eif3h can be seen in rpl24b/stv1-1 [21].
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3020687&req=5

Figure 3: eif3h phenotypes reminiscent of defects in auxin transport or response. (A) eif3h naked shoot. Compared to the canonical pins of the pin1 mutant (B), eif3h pins tended to bear scaly, rudimentary organs. (C) eif3h siliques show defects in carpel development, similar to those of rpl24b/stv1-1 or ett-2, an allele of ARF3. White arrowheads point to the last node carrying stamens and red arrowheads point to the basal end of the carpel valves. (D) Rare monocotyledon phenotype of eif3h seedlings, similar to that of mp, an allele of ARF5. (E) Cotyledons were cleared to reveal defects in vascular development. Similar defects as in eif3h can be seen in rpl24b/stv1-1 [21].
Mentions: The emerging hypothesis that RPL24B cooperates with eIF3h predicts that mutations in the two genes have overlapping developmental phenotypes. Instead of a functional inflorescence with leaves and flowers, eif3h mutant plants sometimes formed a pin-formed shoot, especially when shifted from short-day to long-day growth conditions (20%, n = 90) (Fig. 3A). Pin-formed shoots are characteristic of defects in auxin transport or response, for example the pin1 mutant (Fig. 3B[27]) and mutations in the auxin response transcription factor, MONOPTEROS (MP)/ARF5 [35]. These data suggest that eIF3h may boost translation of proteins needed for auxin transport or auxin response. In further support of auxin response defects, some eif3h mutant seedlings had only a single cotyledon or two cotyledons of unequal size, similar to the mp (arf5) mutant (Fig. 3D) and rpl24b/stv1 [21]. Auxin defects often reveal themselves by cul-de-sac vascular elements in the cotyledons, and such defects were readily observed in the eif3h mutant (Fig. 3E).

Bottom Line: Like AtbZip11, the uORF-containing ARF mRNAs are indeed undertranslated in eif3h mutant seedlings.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Genome Science and Technology Program, The University of Tennessee, Knoxville, TN 37996, USA.

ABSTRACT

Background: 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 SHORT VALVE1, likewise fosters translation of uORF-containing mRNAs, for example mRNAs for auxin response transcription factors (ARFs).

Results: Here we tested the hypothesis that RPL24B and eIF3h affect translation reinitiation in a similar fashion. First, like eif3h mutants, rpl24b mutants under-translate the AtbZip11 mRNA, and the detailed spectrum of translational defects in rpl24b is remarkably similar to that of eif3h. Second, eif3h mutants display defects in auxin mediated organogenesis and gene expression, similar to rpl24b. Like AtbZip11, the uORF-containing ARF mRNAs are indeed undertranslated in eif3h mutant seedlings.

Conclusion: 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.

Show MeSH
Related in: MedlinePlus