microRNA access to the target helicases from rice.

Major classes of small RNAs include microRNAs (miRNAs) and small interfering RNAs (siRNAs). miRNAs are single-stranded RNA molecules of around 22 nucleotides in length. Most miRNAs show imperfect homology with their targets. The biogenesis mechanisms of miRNAs are different for plant and animals. Silencing of genes by miRNAs may serve as an appropriate tool to speed-up analyses of gene functions in a post-genome era. We have identified in silico a set of miRNAs that control helicase gene expression by regulating its mRNA stability and translation in rice. Our analysis revealed that several rice helicases have distinct miRNA specificities. Such analyses will be a prerequisite to refining our understanding of target selection and regulation of helicase gene expression by miRNAs in rice. Further, we discuss recent findings on miRNA gene family and its gene structure, criteria for miRNA annotation and on miRNA biogenesis that involve transcription, processing and maturation of miRNAs.