A bona fide La protein is required for embryogenesis in Arabidopsis thaliana.
Searches in the Arabidopsis thaliana genome using the La motif as query revealed the presence of eight La or La-like proteins. Using structural and phylogenetic criteria, we identified two putative genuine La proteins (At32 and At79) and showed that both are expressed throughout plant development but at different levels and under different regulatory conditions. At32, but not At79, restores Saccharomyces cerevisiae La nuclear functions in non-coding RNAs biogenesis and is able to bind to plant 3'-UUU-OH RNAs. We conclude that these La nuclear functions are conserved in Arabidopsis and supported by At32, which we renamed as AtLa1. Consistently, AtLa1 is predominantly localized to the plant nucleoplasm and was also detected in the nucleolar cavity. The inactivation of AtLa1 in Arabidopsis leads to an embryonic-lethal phenotype with deficient embryos arrested at early globular stage of development. In addition, mutant embryonic cells display a nucleolar hypertrophy suggesting that AtLa1 is required for normal ribosome biogenesis. The identification of two distantly related proteins with all structural characteristics of genuine La proteins suggests that these factors evolved to a certain level of specialization in plants. This unprecedented situation provides a unique opportunity to dissect the very different aspects of this crucial cellular activity.
Fleurdépine
Sophie
S
CNRS UMR6547 GEEM, Université Blaise Pascal, 63177 Aubière, France and CNRS UMR5096 LGDP, Université de Perpignan Via Domitia, 66860 Perpignan, France.
Deragon
Jean-Marc
JM
Devic
Martine
M
Guilleminot
Jocelyne
J
Bousquet-Antonelli
Cécile
C
D017360:Arabidopsis / Q000196:embryology* / Q000235:genetics / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000145:classification / Q000235:genetics / Q000502:physiology*; D002466:Cell Nucleolus / Q000648:ultrastructure; D002467:Cell Nucleus / Q000737:chemistry; D002470:Cell Survival; D017353:Gene Deletion; D005804:Genes, Lethal; D012275:Oryza / Q000235:genetics; D010802:Phylogeny; D010940:Plant Proteins / Q000145:classification / Q000235:genetics; D026721:RNA 3' End Processing; D012320:RNA Polymerase III / Q000235:genetics; D012322:RNA Precursors / Q000378:metabolism; D022661:RNA, Untranslated / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000145:classification / Q000235:genetics / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics
D029681:Arabidopsis Proteins; D010940:Plant Proteins; D012320:RNA Polymerase III; D012322:RNA Precursors; D022661:RNA, Untranslated; D016601:RNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; C520620:La2 protein, Arabidopsis; C088396:LHP1 protein, S cerevisiae; C520619:La1 protein, Arabidopsis