Translation elongation factor-1α is pivotal for plant heat tolerance despite its pronounced heat-induced aggregation

The translation elongation factor 1α (EF1α) protein is a highly conserved G protein that is crucial for protein translation in all eukaryotic organisms. EF1α quickly became insoluble at temperatures 42 °C treatment for 2h in vitro, but generally remained soluble in vivo even after being exposed to temperatures as high as 45 °C for an extended period, which suggests that protective mechanisms exist for keeping EF1α soluble in plant cells under heat stress. EF1α had fast in vivo insolubilization when exposed to 45 °C, resulting in about 40% of the protein aggregating after 9 h. Given its established role in protein translation, heat-induced aggregation is most likely to impact the function of the elongation factor. Overexpression of constitutive mutants in both GTP-bound and GDP-bound forms of EF1α resulted in significantly decreased heat tolerance. These findings provide evidence to support the critical role of EF1α, a thermosensitive protein, in the heat tolerance of plants.