Translational Regulation of Plant Response to High Temperature by a Dual-Function tRNAHis Guanylyltransferase in Rice.

As sessile organisms, plants have evolved numerous strategies to acclimate to changes in environmental temperature. However, the molecular basis of this acclimation remains largely unclear. In this study we identified a tRNAHis guanylyltransferase, AET1, which contributes to the modification of pre-tRNAHis and is required for normal growth under high-temperature conditions in rice. Interestingly, AET1 possibly interacts with both RACK1A and eIF3h in the endoplasmic reticulum. Notably, AET1 can directly bind to OsARF mRNAs including the uORFs of OsARF19 and OsARF23, indicating that AET1 is associated with translation regulation. Furthermore, polysome profiling assays suggest that the translational status remains unaffected in the aet1 mutant, but that the translational efficiency of OsARF19 and OsARF23 is reduced; moreover, OsARF23 protein levels are obviously decreased in the aet1 mutant under high temperature, implying that AET1 regulates auxin signaling in response to high temperature. Our findings provide new insights into the molecular mechanisms whereby AET1 regulates the environmental temperature response in rice by playing a dual role in tRNA modification and translational control.