Functional complementation by wheat elF2α in the yeast GCN2-mediated pathway

Translational control by specific eIF2 alpha phosphorylation on serine 51 has been characterized in all eukaryotes with the significant exception of plants. In order to evaluate the capability of plant eIF2 alpha to functionally control translation, the wild type (51S) and a nonphosphorylatable mutant (51A) of wheat eIF2 alpha were expressed in a yeast genetic system. Expression of either wheat protein did not handicap growth under conditions that repress the eIF2 alpha phosphorylation pathway. However, under conditions that induce specific eIF2 alpha phosphorylation only strains expressing wheat 51S were able to grow between 2 and 4 days. Growth was dependent upon activity of yeast, eIF2 alpha kinase GCN2 and resulted in the increased translation of GCN4. The association between plant eIF2 alpha and yeast eIF2B is supported by their specific coimmunoprecipitation from transgenic yeast cells. These data support the similarity among eukaryotic translational initiation processes and strengthen the concept that plants may contain an eIF2 alpha phosphorylation pathway. (C) 2000 Academic Press.