This correlates with an obvious conservation of the TAS3 and miR390 loci between these plant groups [6, 9, 15].
We attempted to reveal miR390 sequences using our PCR-based approach  previously developed for TAS3 genes.
Search for Novel TAS3 Genes in Bryophyta and Marchantiophyta.
It seems this role is more complicated than simple triggering of the TAS3 precursor processing if we assume potential involvement of miR390 in the direct targeting and cleavage of protein-coding mRNAs [41, 42].
All three revealed TAS6 loci are positioned in close genomic proximity to PpTAS3 loci (viz., PpTAS3a, PpTAS3d, and PpTAS3f) (Table 1) and expressed as common RNA precursors with these TAS3 species (Table 1) [15, 20, 38].
Little is known about the miR390/TAS3-based formation of tasiRNAs in ferns , and the selection pressures that influenced the structure of TAS3 genes in diverse taxonomic groups of ferns and fern allies (particularly, classes Lycopodiopsida, Equisetopsida, Marattiopsida, and Polypodiopsida) remain obscure.
To achieve an understanding on the evolutionary history of TAS3 genes in ferns, we focused on two aims (1) identifying possible TAS3 genes in 4 fern orders and (2) unraveling the pattern of TAS3 sequence organization among fern lineages.
Our data on additional plant lineages indicate that the main mechanism of TAS3 gene evolution that could generate diversity is the duplication and divergence of TAS3 loci.
Recently, we revealed that the conserved TAS3 locus (TAS3-Sen1) in Senecio talinoides, Curio repens, and Curio articulatus was actively transcribed, and its close relatives are distributed among many Asteraceae plants and found to be similar to Arabidopsis AtTAS3a gene .
Since reverse transcription priming with the oligo (dT) at the poly A tails of the TAS3 genes analyzed may not occur with the same efficiency, we used correct priming with six-specific primers during PCR on the total cDNA preparation.
Herz et al., "mir390, arabidopsis TAS3 tasiRNAs, and their AUXIN RESPONSE FACTOR targets define an autoregulatory network quantitatively regulating lateral root growth," Plant Cell, vol.
Fan, "Molecular phylogeny of miR390-guided trans-acting siRNA genes (TAS3) in the grass family," Plant Systematics and Evolution, vol.