Reference "A single base change altered the regulation of the Waxy gene at the posttranscriptional level during the domestication of rice"

Reference ID

1430

Title

A single base change altered the regulation of the Waxy gene at the posttranscriptional level during the domestication of rice

Source

Molecular biology and evolution, 1998, vol. 15, pp. 978-987

Authors (3)

Hirano-H-Y	Eiguchi-M
Sano-Y

Abstract

The rice waxy (wx) locus has two functional alleles, Wxa and Wxb, which are
defined by a large difference in the amount of the gene product, called Wx
protein, that accumulates in mature seeds. To elucidate the molecular mechanism
underlying this difference and to identify the base change causing the
alteration of the regulation of the Wx gene during rice evolution, we determined
the nucleotide sequences of the regulatory region of Wx alleles and analyzed
their function in a transient assay system using rice protoplasts. All Wxa
alleles from Oryza sativa Indica, O. rufipogon, and O. glaberrima have a normal
sequence of GT at the 5' splice junction of the first intron, representing a
high expression level of the Wx transcripts in the endosperm and a high beta-
glucuronidase (GUS) activity in protoplasts. On the other hand, Wxb alleles from
two strains of O. sativa Japonica have TT at the 5' splice junction,
representing a low expression level of the mature transcripts and a low GUS
activity. Northern blot analysis also indicated that a larger transcript,
consisting of the unspliced first intron, is closely correlated with the
function of the Wxb allele. These results suggest that a single base change at
the 5' splice junction causes inefficient splicing and, as a result, reduces the
level of mature transcript and the GUS activity in the Wxb allele. The Wxb
allele in O. saativa Japonica may have been differentiated from the Wxa allele
of O. rufipogon, its wild progenitor, by this mutation, and, therefore, a single
base change that has altered the regulation of the Wx gene at the
posttranscriptional level probably occurred during the domestication of rice.