A SNP associated with alternative splicing of RPT5b causes unequal redundancy between RPT5a and RPT5b among Arabidopsis thaliana natural variation.
BACKGROUND
The proteasome subunit RPT5, which is essential for gametophyte development, is encoded by two genes in Arabidopsis thaliana; RPT5a and RPT5b. We showed previously that RPT5a and RPT5b are fully redundant in the Columbia (Col-0) accession, whereas in the Wassilewskia accession (Ws-4), RPT5b does not complement the effect of a strong rpt5a mutation in the male gametophyte, and only partially complements rpt5a mutation in the sporophyte. RPT5bCol-0 and RPT5bWs-4 differ by only two SNPs, one located in the promoter and the other in the seventh intron of the gene.


RESULTS
By exploiting natural variation at RPT5b we determined that the SNP located in RPT5b intron seven, rather than the promoter SNP, is the sole basis of this lack of redundancy. In Ws-4 this SNP is predicted to create a new splicing branchpoint sequence that induces a partial mis-splicing of the pre-mRNA, leading to the introduction of a Premature Termination Codon. We characterized 5 accessions carrying this A-to-T substitution in intron seven and observed a complete correlation between this SNP and both a 10 to 20% level of the RPT5b pre-mRNA mis-splicing and the lack of ability to complement an rpt5a mutant phenotype.


CONCLUSIONS
The accession-dependent unequal redundancy between RPT5a and RPT5b genes illustrates an example of evolutionary drifting between duplicated genes through alternative splicing.
Guyon-Debast
Anouchka
A
Institut National de la Recherche Agronomique-UR1052 Station de Génétique et d'Amélioration des Fruits et Légumes, Domaine Saint Maurice, BP94, F84143, Montfavet, France.
Lécureuil
Alain
A
Bonhomme
Sandrine
S
Guerche
Philippe
P
Gallois
Jean-Luc
JL
D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism; D017398:Alternative Splicing; D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D020641:Polymorphism, Single Nucleotide / Q000235:genetics*
D029681:Arabidopsis Proteins; D000251:Adenosine Triphosphatases; C541999:RPT5a protein, Arabidopsis; C542000:RPT5b protein, Arabidopsis