The final size of an organism depends on the size and the number of its cells. The mechanisms governing the increase in cell number have been extensively studied, but investigation on the molecular basis of cell growth is in its early stages. Progress on y east and animal cells has determined that the protein kinase TOR has a central role in this process.
TOR protein is able to integrate inputs from nutrient availability, growth factors and energy status of the cell to activate all the processes required for mass accumulation. TOR protein can be part of two distinct protein complexes, TORC1 and TORC2, identified in yeast and animal cells. Disruption the homologue of TOR (AtTOR) in Arabidopsis thaliana leads to the premature arrest of endosperm and embryo development.
In addition, AtRAPTOR, a phylogenetically conserved member of TORC1, has an essential role in plant cell development. The present project is aimed for characterizing at the molecular level the TOR dependent signalling in the model plant Arabidopsis thaliana, that is, to obtain new information on the proteins that physically interact with AtTOR, its downstream targets and the physiological signals that AtTOR is able to integrate. For this purpose we will perform different strategies, both in the yeast system (Saccharomyces cerevisiae) and in plants.
We plan to screen for cDNAs of Arabidopsis thaliana able to suppress the lethality of yeast mutant strains defective in essential components of TOR dependent signalling. We will also immunoprecipitate AtT OR from plant tissues and identify the Co-purifying proteins by mass-spectrometry. In parallel, we will investigate which hormonal or nutritional signals are able to activate or block AtTOR signalling.
Finally we will study the effect of the gain or loss o f function of the identified genes in the whole plant. These studies will render profitable information about the regulation of plant cell growth and on limiting factors for biomass production.
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