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Funct Integr Genomics. 2009 Aug;9(3):363-76. doi: 10.1007/s10142-009-0121-3. Epub 2009 Mar 28.

Alternative splicing, activation of cryptic exons and amino acid substitutions in carotenoid biosynthetic genes are associated with lutein accumulation in wheat endosperm.

Author information

1
CSIRO Food Futures National Research Flagship, Canberra, Australia. Crispin.Howitt@csiro.au

Abstract

Endosperm carotenoid content in wheat is a primary determinant of flour colour and this affects both the nutritional value of the grain and its utility for different applications. Utilising wheat rice synteny two genes, epsilon-cyclase (epsilon-LCY) and phytoene synthase (Psy-A1), were identified as candidate genes for two of the QTL affecting lutein content in wheat endosperm. Analysis of the sequence changes in epsilon-LCY and Psy-A1 revealed possible causal mechanisms for both QTL. A point mutation in epsilon-LCY results in the substitution of a conserved amino acid in the high lutein allele. This substitution has been observed in high lutein-accumulating species from the Gentiales order. In Psy-A1, a sequence duplication at the end of exon 2 creates a new splice site and causes alternative splicing of the transcript and activation of a cryptic exon, resulting in four different transcripts: a wild-type transcript, two transcripts with early terminations and a transcript that would produce an in-frame, albeit longer protein. Only the wild-type splice variant produced an enzymatically active protein and its mRNA abundance was reduced by titration with the other splice variants. This reduction in wild-type mRNA is argued to result in a reduction in PSY protein and thus carotenoid content in wheat.

PMID:
19330366
DOI:
10.1007/s10142-009-0121-3
[Indexed for MEDLINE]

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