Lilley JL, Gee CW, Sairanen I, Ljung K, Nemhauser JL
An endogenous carbon-sensing pathway triggers increased auxin flux and hypocotyl elongation
Plant Physiol. 2012 Oct 16. [Epub ahead of print]

Abstract
The local environment has a substantial impact on early seedling development. Applying excess carbon in the form of sucrose is known to alter both timing and duration of seedling growth. Here, we show that sucrose changes growth patterns by increasing auxin levels and rootward auxin transport. Sucrose likely interacts with an endogenous carbon-sensing pathway via the PHYTOCHROME INTERACTING FACTOR (PIF) family of transcription factors, as plants grown in elevated CO2 showed the same PIF-dependent growth promotion. Overexpression of PIF5 was sufficient to suppress photosynthetic rate, enhance response to elevated CO2, and prolong seedling survival in nitrogen limiting conditions. Thus, PIF transcription factors integrate growth with metabolic demands, and thereby facilitate functional equilibrium during photomorphogenesis.

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