Reference "A naturally occurring functional allele of the rice waxy locus has a GT to TT mutation at the 5' splice site of the first intron"

Reference ID

1671

Title

A naturally occurring functional allele of the rice waxy locus has a GT to TT mutation at the 5' splice site of the first intron

Source

The Plant journal : for cell and molecular biology, 1998, vol. 15, pp. 133-138

Authors (7)

Isshiki-M	Morino-K
Nakajima-M	Okagaki-R-J
Wessler-S-R	Izawa-T
Shimamoto-K

Abstract

In cultivated rice two wild-type alleles, Wxa and Wxb, predominate at the waxy
locus, which encodes granule-bound starch synthase. The activity of Wxa is 10-
fold higher than that of Wxb at the level of both protein and mRNA. Wxb has a
+1G to T mutation at the 5' splice site of the first intron. Sequence analysis
of Wxb transcripts revealed that splicing occurs at the mutant AG/UU site and at
two cryptic sites: the first is A/GUU, one base upstream of the original site
and the second is AG/GU found approximately 100 bases upstream of the mutant
splice site. We introduced single base mutations to the 5' splice sites of both
Wxa and Wxb, fused with the gus reporter gene and introduced them into rice
protoplasts. Analysis of GUS activities and transcripts indicated that a G to T
mutation in Wxa reduced GUS activity and the level of spliced RNA. Conversely, a
T to G mutation of Wxb restored GUS activity and the level of spliced RNA to
that of wild-type Wxa. These results demonstrated that the low level expression
of Wxb results from a single base mutation at the 5' splice site of the first
intron. It is of interest that the Wxb allele of rice carrying the G to T
mutation of intron 1 has been conserved in the history of rice cultivation
because there is a low amylose content of the seed caused by this mutation.