Abstract

Eukaryotes contain a diversified set of small RNA -guided pathways that control genes, repeated sequences and viruses at the transcriptional and posttranscriptional level. These pathways form microRNAs and siRNAs, and are essential for multicellular development, genome maintenance and integrity, rapid responses to biotic and abiotic stress, and defense. Genome-wide profiling and analyses of small RNAs and transcripts was done for wild-type Arabidopsis thaliana and silencing pathway mutants with defects in three RNA -DEPENDENT RNA POLYMERASE (RDR) and four DICER -LIKE (DCL) genes. Profiling involves direct analysis using a multiplexed, parallel sequencing strategy. This revealed diverse populations of small RNAs that target specific classes of genetic elements. The most abundant small RNA class is dependent on RDR2 and DCL3 , and targets repetitive elements across the genome. The presentation will focus on functional diversification of small RNA pathways, and how these pathways may influence the shape of plant genomes.

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