Association between allelic variation at the Phytoene synthase 1 gene and yellow pigment content in the wheat grain

Abstract

A better understanding of the genetic factors controlling grain yellow pigment content (GYPC) is important for both pasta (high GYPC) and bread wheat (low GYPC) quality improvement. Quantitative trait loci (QTL) for GYPC have been mapped repeatedly on the distal regions of chromosome arms 7AL and 7BL in wheat, and the Phytoene synthase 1 (PSY-1) gene located in this region has been proposed as a candidate gene. We show here that PSY-E1, the tall wheatgrass orthologue, is completely linked to diVerences in GYPC, and that selection for white endosperm mutants in recombinant lines carrying this gene resulted in the identiWcation of a mutation in a conserved amino acid of PSY-E1. These results, together with the association between GYPC and allelic diVerences in PSY-1 in hexaploid wheat, suggest that this gene plays an important role in the determination of GYPC. However, a second white endosperm mutant previously mapped to chromosome arm 7EL showed no mutations in PSY-E1 suggesting the existence of additional gene(s) aVecting GYPC in this chromosome region. This hypothesis was further supported by the mapping of QTL for GYPC on 7AL proximal to PSY-1 in a cross between pasta wheat varieties UC1113 and Kofa. Interestingly, the Kofa PSY-B1 allele showed unusually high levels of polymorphisms as a result of a conversion event involving the PSY-A1 allele. In summary, our results support the hypothesis that allelic diVerences in PSY-1 and at least one additional gene in the distal region of the long arm of homoeologous group 7L are associated with diVerences in GYPC.

Provitamin A Accumulation in Cassava (Manihot esculenta) Roots Driven by a Single Nucleotide Polymorphism in a Phytoene Synthase Gene

“…The sequence diversity of PSY1 in grasses has been assessed (Fu et al, 2010), revealing a hot spot of nonsynonymous substitutions residing in a region located ;115 amino acids closer to the N terminus than the exchange reported here. In addition, allelic PSY1 variants of durum wheat were found to be associated with high endosperm carotenoid contents (Zhang and Dubcovsky, 2008;Singh et al, 2009), but none of these mutations were in a position equivalent to the one reported here. Whereas A191D appears to be a rare variant, its activity-increasing effect was similar in all the mutagenized PSY homologs investigated.…”

The Potential of Lr19 and Bdv2 Translocations to Improve Yield and Disease Resistance in the High Rainfall Wheat Zones of Australia

“…Both T4m1 and T4m2 were developed through an EMS mutagenesis screen with selection based upon white flour colour [9]. Zhang and Dubcovsky [15] surmised that the different mutations in the original translocation were responsible for the white flour colour in these two lines but it was not clear which regions within the translocation were affected. These mutations did not affect leaf rust resistance however T4m1 retained the effective Sr25 locus whilst T4m2 did not [3], indicating this latter mutation line may have an abnormal makeup following the mutagenic treatment.…”

Cloning and allelic variation of two novel catalase genes (SoCAT-1andSsCAT-1) inSaccharum officinarumL. andSaccharum spontaneumL.

“…The direct effect of allelic variation is a change in the corresponding protein coding sequence, which may result in alterations in phenotype and function. [22] However, some allelic variations occur in introns and have no influence on the protein-coding sequence of the gene. [23] Introns may affect the gene transcript by modulating alternative splicing.…”

“…[24] In some genes, insertion/deletion changes in introns may result in changes in the enzymatic activity and thus, in the phenotype. [22] Yau and Simon [25] observed that the insertion of a 2.5 kb sequence in an intron of the soluble acid invertase (SAI) gene altered the transcription and resulted in a significant increase in sucrose content in carrots. Liu et al [26] also reported that a domain of ATTGA repeat sequences in the second intron of the Sai-1 gene in sweet sorghum might be an important regulatory site, and that the functional marker SBX1 was closely related to the Brix value.…”