A defining feature of plant leaves is their flattened shape. This shape depends on an antagonism between the genes that specify adaxial (top) and abaxial (bottom) tissue identity; however, the molecular nature of this antagonism remains poorly understood. Class III homeodomain leucine zipper (HD-ZIP) transcription factors are key mediators in the regulation of adaxial-abaxial patterning. Their expression is restricted adaxially during early development by the abaxially expressed microRNA (MIR)165/166, yet the mechanism that restricts MIR165/166 expression to abaxial leaf tissues remains unknown. Here, we show that class III and class II HD-ZIP proteins act together to repress MIR165/166 via a conserved cis-element in their promoters. Organ morphology and tissue patterning in plants, therefore, depend on a bidirectional repressive circuit involving a set of miRNAs and its targets.
|Number of pages||6|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|Publication status||Published - 2016 Oct 18|
Bibliographical noteFunding Information:
We thank P. N. Benfey, J.-Y. Lee, K. Nakajima, and J. L. Bowman for sharing seeds and plasmids as well as A. Obrdlik, M. Ghosh Dastidar, and A. Vilches-Barro for scientific discussion. M.G.H. acknowledges the European Research Council (GA 261081) and Australian Research Council for current funding. The laboratory of S.W. is supported by grants from the Deutsche Forschungsgemeinschaft (WE4281/7-1), the European Research Council (GA 336295), and start-up funding from the Copenhagen Plant Science Centre. F.O. was supported by Max Planck Society funds to D. Weigel.
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