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. 2007 Nov-Dec;2(6):519–521. doi: 10.4161/psb.2.6.4655

Figure 1.

Figure 1

Models for adaxial/abaxial patterning via TAS3-derivated ta-siRNAs and miR166. (A) LBL1/SGS3 is required for the biogenesis of tasiR-ARFs from tas3 loci on the adaxial (ad) side of the incipient primordium that guide the cleavage of ARF3 transcripts. ARF3 may directly regulate the expression of specific mir166 family members, such as mir166c. (B) Additional TAS3-derivated siRNAs may guide the cleavage of novel targets (X) that directly or indirectly regulate the expression of mir166 family members. Mature miR166 accumulates on the abaxial (ab) side of the initiating leaf and confines the expression of the HD-ZIPIII family members to the adaxial surface. The opposing activities of TAS3-derivated ta-siRNAs and miR166 thus specifies polarity in the developing leaves.