Genetic strategies to reveal system properties of patterning processes

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Proper plant patterning is important for optimized growth performance, plant architecture and biomass, plant regeneration properties and stem cell allocation. An amazing suite of recent results has linked seemingly separate patterning processes, including embryo axis formation, meristem organization, lateral organ positioning and vascular patterning to the polar transport of the phyotohormone auxin. Based on previous work on Auxin Response Factors (ARFs) we have set up optimized genetic backgrounds for investigating the systems properties of auxin mediated patterning processes: (1) After discovering the equivalence of auxin foucssing mechanisms in the shoot meristem and in leaves, we are taking advantage of the better experimental and mathematical accessibility of the leaf system. Here we will explore the systems properties of self-regulatory auxin patterning, using novel visualization and unique local interference tools. Specifically, spatially and temporally highly controlled activity of MP/ARF5 in multiple mutant background can serve as an ideal switch to turn on/off auxin mediated patterning in numerous locations. Because equivalent mechanisms in the shoot meristem, the findings will have implications for the entire shoot architecture. (2) In a complementing line of research, we have identified the relative contributions of five ARFs with activating (Q-rich) middle domains in patterning processes, including immediate target genes and nodes of interaction with co-regulators of the Aux/IAA family. (3) Along a third line, we have identified and molecularly characterized a first suppressor of ARF function, which defines a largely unexplored antagonistic pathway. We will explore this and other ARF antagonizing pathways using genetic and molecular approaches. Finally, (4) our genomic work on genes in early vascular development downstream of ARF regulation leads us into the exploration of the transcription factor hierarchy in vascular tissue specification.