Plant Molecular Biology 41: 801–813, 1999. © 1999 Kluwer Academic Publishers. Printed in the Netherlands. 801 The eEFlA gene family is differentially expressed in maize endosperm Newton P. Carneiro 1 , Peter A. Hughes 2 and Brian A. Larkins ∗ Department of Plant Sciences, University of Arizona, Forbes Hall, Room 303, Tucson, AZ 85721, USA ( ∗ author for correspondence); current addresses: 1 CNPMS/EMBRAPA, Caixa Postal 151, CEP 35701-970, Sete Lagoas, MG, Brazil; 2 CSIRO Plant Industry, P.O. Box 1600, Canberra ACT 2601, Australia Received 21 July 1999; accepted in revised form 14 October 1999 Key words: eEF1A, endosperm, gene family, maize, opaque2 Abstract eEF1A appears to be a multifunctional protein in eukaryotes, where it serves as a protein synthesis factor as well as a cytoskeletal protein. In maize endosperm, the eEF1A concentration is highly correlated with lysine content, and eEF1A synthesis is increased in opaque2 mutants compared to wild type. To investigate the basis for the increased synthesis of eEF1A in opaque2, we characterized the genes encoding this protein and measured their relative level of expression in endosperm and other tissues. Maize contains 10 to 15 eEF1A genes that are nearly identical in nucleotide and amino acid sequences. However, these genes can be distinguished based on their 3 ′ non-coding sequences, which are less conserved. By screening endosperm and seedling cDNA libraries, we show that most of the maize eEF1A genes are expressed, and the relative level of their transcripts varies in different tissues. At least five genes are transcribed in the endosperm, and two account for ca. 80% of the RNA transcripts. The expression of several genes is enhanced in opaque2 endosperm, although the significance of this is unclear. Abbreviations: eEF1A, elongation factor 1A; o2, opaque2 Introduction eEF1 is a protein synthesis factor composed of four subunits: A, Bα,Bβ and Bγ (Browning, 1996). Sub- unit eEF1A, also known as EF-1α, binds aminoacyl- tRNAs to the acceptor (A) site of the ribosome during the peptide chain elongation phase of protein syn- thesis. However, eEF1A appears to be involved in a number of other cellular processes. It was found to associate with the centromere (Kuriyama et al., 1990) and mitotic apparatus (Ohta et al., 1990) of sea urchin eggs and attach to the endoplasmic retic- ulum membrane of Chinese hamster fibroblast cells (Hayashi et al., 1989). It interacts in vitro with a number of proteins, including the valyl-tRNA syn- thase complex (Motorin et al., 1988), actin (Yang The nucleotide sequence data reported will appear in the EMBL, GenBank and DDBJ Nucleotide Sequence Databases under the accession numbers AF136823 (eEF1Aa), AF136824 (eEF1Ab), AF136825 (eEF1Ac), AF136826 (eEF1Ad), AF136827 (eEF1Ae), AF136828 (eEF1Af) and AF136829 (eEF1Ag). et al., 1990; Collings et al., 1994), tubulin (Durso and Cyr, 1994) and calmodulin (Kaur and Ruben, 1994). When isolated from the plasma membrane of carrot suspension cells, eEF1A was found to activate phosphatidylinositol 4-kinase (Yang et al., 1993). In Dictyostelium, bundling of actin by eEF1A was re- ported to be pH-dependent in a physiological range that coincides with the dependence of protein syn- thesis on pH (Edmonds et al., 1995). This activity of the protein does not appear to alter its enzymatic properties (Edmonds et al., 1998). These observations suggest that eEF1A behaves as a multifunctional pro- tein, although the biological significance of many of these interactions is not fully understood. eEF1A has a high (10%) lysine content, and the protein is subject to several post-translational mod- ifications. In the fungus Mucor, it was shown that 8 of 44 lysine residues can be methylated, a change that appeared to alter the affinity for aminoacyl tRNAs (Hiatt et al., 1982; Fonzi et al., 1985). However, an