Characterization of eukaryotic translation initiation factor 3 subunits (eIF3) in A. thaliana male gametophyte

From RNA-to-protein, translation initiation and protein synthesis is mediated by trans-acting factors that recognize mRNA features common to almost all eukaryotes. Eukaryotic translation initiation factor 3 complex (eIF3) is a highly conserved protein complex that recognizes 5'-CAP elements of the mRNA to initiate translation. eIF3 consists of nine subunits, three of them having two isoforms: eIF3A, eIF2B1, eIF3B2, eIF3C1, eIF3C2, eIF3D, eIF3E, eIF3F, eIF3G1, eIF3G2, eIF3H and eIF3K. This work deals with functional characterization, expression and subcellular localization of eIF3B1, eIF3B2 and eIF3E in Arabidopsis thaliana male gametophyte and interaction of eIF3E with the Constitutive photomorphogenesis 9 (COP9) complex as a regulatory complex of eIF3E post-translational control. Here we show that depletion of eif3b1 or eif3b2 is not gametophytic lethal and that the two protein might function redundantly, whereas, knockout of eIF3E causes male gametophyte lethality. Interestingly, eif3b1 show post-fertilization defects during embryogenesis, suggesting that its redundancy with eIF3B2 is restricted to the gametophyte. Gene expression studies revealed high expression of eIF3 subunits in actively dividing zones of leaf primordia, root meristem and root elongation zones as well as in the vegetative..