Identification and expression-profiling of Xenopus tropicalis miRNAs including plant miRNA-like RNAs at metamorphosis

Small RNAs (miR159-like RNAs) identical to some plant miR159s were found in Xenopus tropicalis miRNA cDNA libraries (30 miRNA families consisting of 75 unique sequences). Preferential expression of this RNA species was found in neural tissues during development. A sequence matching to this RNA species was not found in the 21 available animal’s genome databases, but its resembling sequences associated with transposons were found in the X. tropicalis database. A possibility of horizontal transfer of the miR159 genes from plants will be discussed. Expression profiles of other miRNA species at metamorphosis were shown by DNA array and/or Northern hybridization.