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. 2000 Oct 10;97(21):11650-4.
doi: 10.1073/pnas.200217597.

AGO1, QDE-2, and RDE-1 are related proteins required for post-transcriptional gene silencing in plants, quelling in fungi, and RNA interference in animals

M Fagard  1 , S Boutet, J B Morel, C Bellini, H Vaucheret
Affiliations

AGO1, QDE-2, and RDE-1 are related proteins required for post-transcriptional gene silencing in plants, quelling in fungi, and RNA interference in animals

M Fagard et al. Proc Natl Acad Sci U S A. .

Abstract

Introduction of transgene DNA may lead to specific degradation of RNAs that are homologous to the transgene transcribed sequence through phenomena named post-transcriptional gene silencing (PTGS) in plants, quelling in fungi, and RNA interference (RNAi) in animals. It was shown previously that PTGS, quelling, and RNAi require a set of related proteins (SGS2, QDE-1, and EGO-1, respectively). Here we report the isolation of Arabidopsis mutants impaired in PTGS which are affected at the Argonaute1 (AGO1) locus. AGO1 is similar to QDE-2 required for quelling and RDE-1 required for RNAi. Sequencing of ago1 mutants revealed one amino acid essential for PTGS that is also present in QDE-2 and RDE-1 in a highly conserved motif. Taken together, these results confirm the hypothesis that these processes derive from a common ancestral mechanism that controls expression of invading nucleic acid molecules at the post-transcriptional level. As opposed to rde-1 and qde-2 mutants, which are viable, ago1 mutants display several developmental abnormalities, including sterility. These results raise the possibility that PTGS, or at least some of its elements, could participate in the regulation of gene expression during development in plants.

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Figures

Figure 1
Figure 1
Alignment of AGO1 with RDE-1, QDE-2, and the seven AGO1-related putative proteins encoded by the Arabidopsis genome. The predicted amino acid sequence of AGO1 protein (GenBank accession number U91995, protein number AAC18440.1) (16) is aligned with that of RDE-1 (AF180730, AAF06159.1), QDE-2 (AF217760, AAF43641.1), ZLL/PNH (AJ223508, CAA11429.1/AF154272, AAD40098.1) (31, 32), AGO2 (AC007654, AAF24585.1), AGO3 (AC007654, AAF24586.1), AGO4 (AC005623, AAC77862.1), AGO5 (AC006929, AAD21514.1), AGO6 (AC003033, AAB91987.1), and with partial predicted amino acid sequence of AGO7 (AC073178) the sequencing of which is in progress. Sequence identities are indicated by filled boxes and conservative changes are shaded. Amino acid coordinates are indicated on the left. Dashes indicated gaps introduced by the MultiAlin (35) algorithm to maximize alignment. The alignment was processed by boxshade Version 3.21. The replacing amino acid in the sequenced ago1-24 allele is indicated above the AGO1 sequence.
Figure 2
Figure 2
Methylation analysis of sgs2 and ago1 mutants compared with L1 plants. Methylation was evaluated by Southern blots of DNA extracted from leaves of adult L1 plants, ago1 mutants, and sgs2 mutants, digested with HpaII and hybridized with the GUS3 probe corresponding to the 3′ part of the GUS ORF (33).
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