Table 1.

Plant and animal miRNAs

Characteristics	Plant miRNAs	Animal miRNA
Complementarity	Almost perfect base-pairing	Usually non-perfect
Gene Targeting	Coding region in the open reading frame	3′ untranslated region
mRNA targeting	Single	Multiple
Major mechanisms of action	Cleavage of mRNA target or inhibition of transcription	Inhibition of translation
Grouping	Often belong to large miRNA gene families	Association in large families is uncommon
Length	Short	Long
RNA Polymerases involved	RNA Pol II e III	RNA Pol II
Preservation during evolution	Often conserved among species	Conservation between species is less common than plants