Reference "Wheat Ec metallothionein genes. Like mammalian Zn2+ metallothionein genes, wheat Zn2+ metallothionein genes are conspicuously expressed during embryogenesis"

Reference ID

9096

Title

Wheat Ec metallothionein genes. Like mammalian Zn2+ metallothionein genes, wheat Zn2+ metallothionein genes are conspicuously expressed during embryogenesis

Source

European journal of biochemistry / FEBS, 1992, vol. 209, pp. 971-976

Authors (4)

Kawashima-I	Kennedy-T-D
Chino-M	Lane-B-G

Abstract

A cDNA library was prepared from the bulk mRNA of mature wheat embryos and
screened with mixed 32P-labeled oligonucleotide probes that encoded parts of the
partial amino-acid sequence for the Zn-containing Ec protein. Each DNA insert in
11 positives from a screen of 10(5) plaques encoded a 5' untranslated and a 3'
untranslated region, in addition to an open reading frame (of 81 amino acids)
which, in every case, corresponded to at least 56 of the 59 amino acids in the
partial polypeptide sequence previously determined for the Ec protein. The three
different mRNA sequences encoded in the cDNA probably correspond to single-copy
genes in the A, B and D genomes of hexaploid wheat. A wheat genomic library was
screened with 32P-labeled cDNA and gave a single positive in a screen of 5 x
10(5) plaques. A 3.1-kb genomic fragment (gf-3.1) was sequenced and a cap site
for the encoded mRNA was determined by primer extension. The gf-3.1 sequence
encodes an intronless mRNA for the Ec protein and contains appreciable amounts
of 5' and 3' flanking sequences. In addition to a putative TATA box, two inverted-
repeat sequences and one direct-repeat sequence, the 5' flank in gf-3.1 contains
a sequence similar to the abscisic-acid-responsive element in other higher-plant
genes but does not contain sequences similar to the metal-responsive elements in
animal metallothionein genes. Consistent with these findings, RNA blotting shows
that accumulation of Ec mRNA is abundant in immature embryos, undetectable in
germinated embryos and can be induced by adding abscisic acid, but not by adding
Zn2+ to the medium in which mature wheat embryos are germinated. The findings
suggest that the wheat Ec metallothionein genes, like mammalian liver
metallothionein genes, are conspicuously expressed during embryogenesis.