Hornitschek P, Kohnen MV, Lorrain S, Rougemont J, Ljung K, López-Vidriero I, Franco-Zorrilla JM, Solano R, Trevisan M, Pradervand S, Xenarios I, Fankhauser C
Phytochrome interacting factors 4 and 5 control seedling growth in changing light conditions by directly controlling auxin signaling
Plant J. 2012 71(5):699-711

Plant growth is strongly influenced by the presence of neighbors competing for light resources. In response to vegetational shading shade-intolerant plants such as Arabidopsis display a suite of developmental responses known as the shade avoidance syndrome (SAS). The phytochrome B (phyB) photoreceptor is the major light sensor mediating this adaptive response. The control of the SAS occurs in part with phyB directly controlling protein abundance of Phytochrome Interacting Factors 4 and 5 (PIF4 and PIF5). The shade avoidance response also requires rapid biosynthesis of auxin and its transport to promote elongation growth. The identification of genome-wide PIF5 binding sites during shade avoidance reveals that this bHLH transcription factor regulates the expression of a subset of previously identified SAS genes. Moreover our study suggests that PIF4 and PIF5 regulate elongation growth by directly controlling the expression of genes coding for auxin biosynthesis and auxin signaling components.

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