Genetic interactions between leaf polarity-controlling genes and ASYMMETRIC LEAVES1 and 2 in Arabidopsis leaf patterning.

During leaf development, establishment of adaxial-abaxial polarity is essential for normal leaf morphogenesis. This process is known to be strictly regulated by several putative transcription factors, microRNA165/166 (miR165/166), a trans-acting short-interfering RNA (tasiR-ARF), as well as proteins involved in RNA silencing. Among the putative transcription factor genes, ASYMMETRIC LEAVES1 and 2 (AS1 and 2) facilitate the specification of leaf adaxial identity; however, the mechanism by which AS1 and AS2 cooperate with other leaf polarity components remains largely undetermined. In the current study, we characterized the phenotype of mutants by combining as1 and as2 with mutations of several key transcription factors. Our data showed that double mutant plants carrying as1/as2 and rev, phb or phv enhanced as1/as2 defects by producing more severely abaxialized leaves. In contrast, triple mutants, obtained by combining as1/as2 with double mutant filamentous flower yabby3 (fil yab3) or kanadi1 kanadi2 (kan1 kan2), exhibited additive phenotypes. Additionally, while leaves of rev as2 contained high levels of FIL transcripts, only slightly elevated miR165/166 levels were noted, indicating that FIL and miR165/166 act in parallel in leaf patterning. Moreover, 35S::MIR165a/rev as2 transgenic plants resulted in a more severe abaxialized leaf phenotype than the rev and as2 single mutant plants transformed with the same 35S::MIR165a fusion. Genetic interactions between the key regulators during leaf patterning are discussed.