The Arabidopsis proteasome RPT5 subunits are essential for gametophyte development and show accession-dependent redundancy.
We investigated the role of the ubiquitin proteasome system (UPS), which allows proteins to be selectively degraded, during gametophyte development in Arabidopsis thaliana. Three mutant alleles altering the UPS were isolated in the Wassilewskija (Ws) accession: they affect the Regulatory Particle 5a (RPT5a) gene, which (along with RPT5b) encodes one of the six AAA-ATPases of the proteasome regulatory particle. In the heterozygous state, all three mutant alleles displayed 50% pollen lethality, suggesting that RPT5a is essential for male gametophyte development. However, a fourth mutant in the Columbia (Col) accession did not display such a phenotype because the RPT5b Col allele complements the rpt5a defect in the male gametophyte, whereas the RPT5b Ws allele does not. Double rpt5a rpt5b mutants showed a complete male and female gametophyte lethal phenotype in a Col background, indicating that RPT5 subunits are essential for both gametophytic phases. Mitotic divisions were affected in double mutant gametophytes correlating with an absence of the proteasome-dependent cyclinA3 degradation. Finally, we show that RPT5b expression is highly increased when proteasome functioning is defective, allowing complementation of the rpt5a mutation. In conclusion, RPT5 subunits are not only essential for both male and female gametophyte development but also display accession-dependent redundancy and are crucial in cell cycle progression.
Gallois
Jean-Luc
JL
Institut Jean-Pierre Bourgin, Station de Génétique et d'Amélioration des Plantes UR254, Institut National de la Recherche Agronomique, Centre de Versailles, F-78000 Versailles, France. jlgallois@avignon.inra.fr
Guyon-Debast
Anouchka
A
Lécureuil
Alain
A
Vezon
Daniel
D
Carpentier
Virginie
V
Bonhomme
Sandrine
S
Guerche
Philippe
P
D000251:Adenosine Triphosphatases / Q000235:genetics* / Q000502:physiology; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D025461:Feedback, Physiological; D008938:Mitosis / Q000235:genetics / Q000502:physiology; D008969:Molecular Sequence Data; D011058:Pollen / Q000235:genetics / Q000254:growth & development; D046988:Proteasome Endopeptidase Complex / Q000502:physiology*; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
D029681:Arabidopsis Proteins; D021122:Protein Subunits; D046988:Proteasome Endopeptidase Complex; D000251:Adenosine Triphosphatases; C541999:RPT5a protein, Arabidopsis; C542000:RPT5b protein, Arabidopsis