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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
Author(s) -
Isshiki Masayuki,
Morino Kazuko,
Nakajima Midori,
Okagaki Ron J.,
Wessler Susan R.,
Izawa Takeshi,
Shimamoto Ko
Publication year - 1998
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1046/j.1365-313x.1998.00189.x
Subject(s) - intron , splice site mutation , rna splicing , mutant , biology , genetics , locus (genetics) , splice , microbiology and biotechnology , gene , allele , starch synthase , wild type , rna , amylose , starch , biochemistry , amylopectin
Summary In cultivated rice two wild‐type alleles, Wx a and Wx b , predominate at the waxy locus, which encodes granule‐bound starch synthase. The activity of Wx a is 10‐fold higher than that of Wx b at the level of both protein and mRNA. Wx b has a +1G to T mutation at the 5′ splice site of the first intron. Sequence analysis of Wx b 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 Wx a and Wx b , 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 Wx a reduced GUS activity and the level of spliced RNA. Conversely, a T to G mutation of Wx b restored GUS activity and the level of spliced RNA to that of wild‐type Wx a . These results demonstrated that the low level expression of Wx b results from a single base mutation at the 5′ splice site of the first intron. It is of interest that the Wx b 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.