Plant Molecular Biology 36: 137–148, 1998.
1998 Kluwer Academic Publishers. Printed in Belgium.
Isolation, characterization and mRNA expression of four cDNAs encoding
translation elongation factor 1A from rice (Oryza sativa L.)
and Shin-ichiro Ejiri
Institute for Cell Biology and Genetics, Faculty of Agriculture, Iwate University, Ueda, Morioka, Iwate 020,
author for correspondence)
Received 17 January 1997: accepted in revised form 24 August 1997
Key words: cDNA, rice, protein synthesis, elongation factor 1A, developmental stage
sativa L.). The genes encoded by these cDNAs were designated rice elongation factor 1A genes refa1, refa2, refa3
and refa4. The genes encoded identical eEF-1A polypeptides and shared high amino acid identity with eEF1A of
other eukaryotes. Southern blot analysis suggested that some of these refa genes may be organized in a cluster on
the same chromosome within a short distance. PCR analysis of rice genomic DNA showed that refa1 and refa4,and
refa3 and refa2 are in neighboring locations on the rice genome. The mRNAs of the four refa genes accumulated
to nearly equal levels in a variety of tissues and at different stages of growth. Suspension-cultured cells were the
most abundant in refa mRNAs. Dormant seeds contained a small amount of the four refa mRNAs. Transcript
accumulation was highly induced after seed germination, and the same expression levels were maintained even in
old leaf blades of mature plants.
The translation elongation factor-1 (EF-1) consists
of four different subunits in higher eukaryotes. In
plants, they had been termed EF-1
. Although confusing, two subunits of
animal EF-1 corresponding to plant EF-1
had been termed EF-1
. Recently, a new nomenclature for these sub-
units was adopted by the IUBMB committee. They
are termed now eEF1A (the old designation was EF-
(the old designation was EF-1
(the old designation was EF-1
plants) and eEF1B
(the old designation was EF-
) . eEF1A catalyzes GTP-dependent binding
of aminoacyl-tRNA to the acceptor site on the 80S
ribosome concomitant with the hydrolysis of GTP.
The resulting eEF1A
GDP is catalytically converted
The nucleotide sequence data reported will appear in theDDBJ,
EMBL and GenBank Nucleotide Sequence Databases under the
accession numbers D63580 (refa1), D63581 (refa2), D63582 (refa3)
and D63583 (refa4).
GTP by the guanine-nucleotide exchange
factor eEF1B (
). Both eEF1B
been known to possess GDP/GTP exchange activity.
However, the function of eEF1B
at present is still
been done of EF-Tu (bacterial homologue of eEF1A)
from Escherichia coli  and Thermus thermophilus
, and the conformation of the polypeptide chain of
intact EF-Tu and some of the effector region has been
clearly established. EF-Tu consists of three domains:
domain I forms the nucleotide binding domain, and
domain III forms an eEF1B-binding site. In the
presence of GTP, domain I and domain II form an
aminoacyl-tRNA binding cavity.
Several genomic or cDNA clones encoding eEF1A
have been identiﬁed and characterized in a variety
of eukaryotes and archaea. Among them, some spe-
cies have more than two genes encoding eEF1A.
In Saccharomyces cerevisiae, genomic clones encod-
ing eEF1A gene were classiﬁed into two groups by
restriction analysis and Southern hybridization .