Scientists revealed factors involved in miRNA degradation in Arabidopsis

microRNAs (miRNAs) are now known to play regulatory functions in numerous developmental and metabolic processes in plants and animals. The biogenesis of miRNA is also well-established. But until now factors involved in miRNA degradation remain unknown. Ramachandran et al. now report (Science Vol. 321. no. 5895, pp. 1490 – 1492, 2008) a factor that is involved in the miRNA degradation in Arabidopsis plants (small flowering plants related to cabbage and mustard). Ramachandran et al. from University of California Riverside have shown that that a family of exoribonucleases (an exoribonuclease is an exonuclease ribonuclease, which are enzymes that degrade RNA by removing terminal nucleotides from either the 5' end or 3' end of the RNA molecule) encoded by the SMALL RNA DEGRADING NUCLEASE (SDN) genes degrades mature miRNAs in Arabidopsis. SDN1 acts specifically on single-stranded miRNAs in vitro. Ramachandran et al. also showed that knockdown of three SDN genes lead to an elevated miRNA levels and pleiotropic (pleiotropy describes the genetic effect of a single gene on multiple phenotypic traits) developmental defects in Arabidopsis. This piece of information provided by this study is expected to shed more light in the understanding of pathways and factors involved in the degradation of miRNA in other plants and animals.