Abstract
MicroRNAs (miRNAs) are small, noncoding RNAs that can play important roles in eukaryotes by mRNA degradation, and translation repression. To investigate whether miRNAs regulate gene expression in woody plants, we had analyzed small RNAs expressed at flowering stage of Eucalyptus, and then isolated about 500 miRNAs. In those miRNAs, there were many new miRNAs that were not identified in Arabidopsis or Populus. We are searching the miRNA target transcripts, and identified some miRNA target genes so far. One of the target genes has homology with Arabidopsis SPL2 gene, and this gene was expressed in all organs in Eucalyptus. Another target gene has sequence conservation with MYB genes, and this gene was also expressed in every organ except young roots. 5'RLM-RACE demonstrated that these two genes were cleaved in the middle of their target sites. These results indicated that miRNAs regulate gene expression of the transcription factors in Eucalyptus.
