ABSTRACT
MicroRNAs (miRNAs) are small endogenous, non-coding regulatory RNA sequences consisting of 18–22 nucleotides derived from their precursor, sequences which negatively regulate the expression of target mRNAs by initiating mRNAS cleavage or inhibition of mRNA translation. The mature lin-4 RNA defines the mRNA expression of the lin-14 and lin-28 heterochronic genes with the antisense mediated repression mechanism of translation initiation, thus specifies the fate of cells during the first three larval stages. Coffee is one of the most important crops in the world and is the second most traded commodity, an important source of income for several countries. The genus Coffea belongs to the family Rubiaceae and contains more than hundred species. MicroRNAs have been discovered by three basic approaches: direct cloning, forward genetic, direct cloning, forward genetic, bioinformatic prediction followed by experimental validation. The most direct method of microRNA discovery is to isolate and clone small RNAs from biological samples; several groups have used this approach to identify plant miRNAs.
