The Translation Elongation Factor eEF-1Bβ1 Is Involved in Cell Wall Biosynthesis and Plant Development in Arabidopsis thaliana

The eukaryotic translation elongation factor eEF-1B beta 1 (EF1B beta) is a guanine nucleotide exchange factor that plays an important role in translation elongation. In this study, we show that the EF1B beta protein is localized in the plasma membrane and cytoplasm, and that the transcripts should be expressed in most tissue types in seedlings. Sectioning of the inflorescence stem revealed that EF1B beta predominantly localizes to the xylem vessels and in the interfascicular cambium. EF1B beta gene silencing in ef beta caused a dwarf phenotype with 38% and 20% reduction in total lignin and crystalline cellulose, respectively. This loss-of-function mutant also had a lower S/G lignin monomer ratio relative to wild type plants, but no changes were detected in a gain-of-function mutant transformed with the EF1B beta gene. Histochemical analysis showed a reduced vascular apparatus, including smaller xylem vessels in the inflorescence stem of the loss-of-function mutant. Over-expression of EF1B beta in an eli1 mutant background restored a WT phenotype and abolished ectopic lignin deposition as well as cell expansion defects in the mutant. Taken together, these data strongly suggest a role for EF1B beta in plant development and cell wall formation in Arabidopsis.