Biogenesis of Plant MicroRNAs

MATEOS, JL; BOLOGNA, NG; PALATNIK JF

Non-coding RNAs in Plants

Springer

Año: 2011; p. 251 - 268

MicroRNAs (miRNAs) are small RNAs of ~ 21 nt that regulatemultiple biological pathways in complex organisms. They are definedby their specific biogenesis which involves the precise excisionfrom an imperfect fold-back precursor. In plants, the ribonucleaseIII DICER-LIKE1 assisted by accessory proteins cleaves theprecursor to release the miRNA. In general, the processing complexrecognizes a 15 nt lower stem located below the miRNA in the precursorsto produce the first cleavage, which is then followed by a secondcut that releases the small RNA. Plant precursors are, however,very variable in size and shape and not all of them are processed inthe same way. The conserved miR319/159 precursors are cleaved ina loop-to-base direction by several successive DCL1 cuts. The situationseems to be even more complex if newly evolved miRNAs arealso taken into account. The emerging picture suggests a high plasticityof the miRNA processing machinery.