Component of the elongator complex which is required for multiple tRNA modifications, including mcm5U (5-methoxycarbonylmethyl uridine), mcm5s2U (5-methoxycarbonylmethyl-2-thiouridine), and ncm5U (5-carbamoylmethyl uridine) (By similarity). The elongator complex catalyzes the formation of carboxymethyluridine in the wobble base at position 34 in tRNAs (By similarity). Promotes organ development by modulating cell division rate. May regulate mechanisms producing carbon assimilates or importing sucrose. Involved in the repression of the abscisic acid (ABA) signaling pathway during seed germination and seedling growth. Required for auxin distribution or signaling. Involved in oxidative stress signaling. Prevents anthocyanin accumulation. tRNA modification; 5-methoxycarbonylmethyl-2-thiouridine-tRNA biosynthesis. Component of the elongator complex which consists of ELP1/ELO2, ELP2, ELP3/ELO3, ELP4/ELO1, ELP5, and ELP6 (PubMed:20080602). Interacts directly with ELP6 (PubMed:20080602). Expressed in meristematic tissues of roots, leaves, stems, seedlings, cotyledons, flowers, siliques, guard cells, floral buds, and shoot apices. Narrow leaves and reduced root growth that results from a decreased cell division rate and a reduced apical dominance. Delayed germination after imbibition. Enhancement of germination and inhibition of leaf growth at high sucrose concentrations. Hypersensitive to abscisic acid (ABA) in seed germination and seedling growth. At the cellular level, hypotonic vacuole, alterations in the size of grana and starch grains in the chloroplasts, and massive presence of Golgi vesicles in the cytoplasm. Higher resistance to oxidative stress mediated by methyl viologen (MV) that blocks electron transport during photosynthesis and by CsCl in light. Accumulates anthocyanins. Belongs to the ELP4 family. The elongator complex was originally thought to play a role in transcription elongation. However, it is no longer thought to play a direct role in this process and its primary function is thought to be in tRNA modification.