Edinburgh, Scotland, United Kingdom - TAIR

Uniparental expression of PolIV-dependent
siRNAs in the developing endosperm of
Arabidopsis
Most eukaryotes produce small RNA (sRNA) mediators of gene silencing that
bind to Argonaute proteins and guide them, by base pairing, to an RNA target.
Micro(mi)RNAs that normally target mRNAs for degradation or translational
arrest are the best understood class of sRNAs. However, in Arabidopsis thaliana
flowers, miRNAs account for only 5% of the sRNA mass and less than 0.1% of
the sequence complexity. The remaining sRNAs comprise a complex population
of more than 100,000 different small interfering (si) RNA transcribed from
thousands of loci. The biogenesis of most of the siRNAs in Arabidopsis are
dependent on Polymerase IV (PolIV) – a homologue of DNA-dependent RNA
polymerase II. A subset of these PolIV-dependent (p4)-siRNAs are involved in
stress responses and others are associated with epigenetic modifications to DNA
or chromatin but the biological role is not known for most of them. Here we
demonstrate that the predominant phase of p4-siRNA accumulation is initiated
in the maternal gametophyte and continues during seed development.
Expression of p4-siRNAs in developing endosperm is specifically from maternal
chromosomes. Our results provide the first evidence for a link between genomic
imprinting and RNA silencing in plants.
53
C02
Wednesday 14:15 - 14:30
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Rebecca A Mosher1
Charles W Melnyk1
Krystyna A Kelly1
Ruth M Dunn1
David J Studholme2
David C Baulcombe1
1Plant Sciences Department
Cambridge University
Cambridge
UK
2The Sainsbury Laboratory
Norwich
UK