Figure 6. Expression of a tasiR-ARF insensitive arf3a transgene recapitulates the lbl1 phenotype.

(A) Mutations were introduced in both arf3a tasiR-ARF binding sites that reduce complementarity without affecting the amino acid sequence. Sequences of the tasiR-ARF target sites in arf3a and arf3a-m with base pairing to the tas3d D7(+) ta-siRNA, are shown. (B-E) Expression of arf3a-m from the arf3a regulatory regions produces a seedling phenotype with similarities to weak alleles of lbl1 [55]. arf3a:arf3a-m seedlings develop thread-like abaxialized leaves (arrowhead in B) and half leaves (C), as well as leaves with ectopic blade outgrowths surrounding abaxialized sectors on the upper leaf surface radial (D, E). (F) Analogous to the half leaves present in weak lbl1 mutants, half leaves on arf3a:arf3a-m transgenic plants show a partial radial arrangement of vascular bundles around the midvein (arrow). (G) Compared to the near wild-type phenotype of arf3a:arf3a transgenic plants (left) the stature of arf3a:arf3a-m plants (right) is severely reduced. (H-I) Such plants display defects in vegetative and reproductive development. Arrows in (H) mark half leaves, and in (I), a strongly reduced and sterile male inflorescence. Ad, Adaxial; Ab, Abaxial; MV, midvein. Scale bar = 100 µm.