Nutrient sensing and homeostasis

Phosphate (Pi) and zinc are essential plant macro and micronutrients, respectively. Nutrient homeostasis mechanisms insure that plants maintain an adequate nutrient supply in all cell types, at all stages of development and environmental conditions. At the cellular level, homeostasis is the result of uptake, transport and compartmentation activities. To a large extend, plant’s growth and development under the prevailing conditions depends upon their ability to sense nutrients and to respond rapidly to nutrient deficiency. Ultimately, our research aims at a better understanding of the mechanisms of Pi and zinc homeostasis in plants.

 

(I) We explore the possibility of quantifying Pi changes in living cells using a phosphate nanosensor. Fluorescent indicator proteins (FLIPs) consist of a substrate-binding protein linked to two fluorescent reporter proteins. Substrate binding changes the conformation of the nanosensor and the efficiency of fluorescence resonance energy transfer (FRET) between the reporter proteins. A Pi nanosensor has been engineered by fusing a predicted bacterial Pi-binding protein (piBP) from Synechococcus to eCFP and eYFP as FRET partners (Gu et al., 2006). We are trying to measure Pi changes over a wide range (nanomolar to millimolar) with this genetically encoded Pi FRET nanosensor expressed in Arabidopsis.

 

(II) The response and adaptation of plants to low zinc supply involves the induction of expression of a small set of genes that constitutes the primary response to zinc deficiency, insuring the maintenance of zinc homeostasis. We want to understand the regulation of this response in Arabidopsis, the transcription factors involved and their mode of action. How do plants sense zinc deficiency?