Cloning of a higher plant elongation factor 2 cDNA: Expression of eEF2 andalpha subunit of eEF1B in sugar beet cells during phosphate and carbohydrate starvation

In ribosomal protein synthesis of higher plants, the peptide elongation ste p depends, like in other eukaryotic and prokaryotic organisms, on several e longation factors, i.e. eEF1A, eEF1B (composed of three subunits; alpha, be ta, gamma) and eEF2. We have isolated a full-length cDNA clone for eEF2 fro m sugar beet. The eEF2 protein sequence as predicted from the cDNA shows hi ghest homology with eEF2 from Chlorella kessleri, but is also highly simila r to other eukaryotic eEF2s. We have analyzed the transcript amounts for eE F1B (alpha-subunit) and eEF2 in phosphate- and carbohydrate-starved sugar b eet suspension-cultured cells and compared them with the transcript levels present in exponentially growing cells. Phosphate starvation affected growt h but not the expression of both elongation factors. The dramatic decrease of eEF2 mRNA in response to carbohydrate starvation indicates that eEF2 exp ression is more sensitive towards nutrient depletion than expression of the eEF1B alpha-subunit.