Insight into durum wheat Lpx-B1: a small gene family coding for the lipoxygenase responsible for carotenoid bleaching in mature grains.
BACKGROUND
The yellow colour of pasta products is one of the main criteria used by consumers to assess pasta quality. This character is due to the presence of carotenoid pigments in semolina. During pasta processing, oxidative degradation of carotenoid pigments occurs mainly due to lipoxygenase (LOX). In durum wheat (Triticum durum Desf.), two Lpx-1 genes have been identified on chromosome 4B, Lpx-B1.1 and Lpx-B1.2, and evidences have been reported that the deletion of Lpx-B1.1 is associated with a strong reduction in LOX activity in semolina. In the present study, we characterised the Lpx-B1 gene family identified in a durum wheat germplasm collection and related the distribution and expression of the Lpx-B1 genes and alleles to variations in LOX activity in the mature grains.


RESULTS
In addition to the already known Lpx-B1.1 and Lpx-B1.2 genes, a new gene was identified, Lpx-B1.3, along with three different Lpx-B1.1 alleles, Lpx-B1.1a, Lpx-B1.1b and the partially deleted Lpx-B1.1c. Screening of the germplasm collection showed that all of the genotypes have one of the three Lpx-B1.1 alleles, associated with either Lpx-B1.2 or Lpx-B1.3, thus showing that in this collection the two genes are alternatives. Therefore, based on Lpx-B1 distribution, three different haplotypes were distinguished: haplotype I, carrying Lpx-B1.3 and the Lpx-B1.1b allele; haplotype II carrying Lpx-B1.2 and the Lpx-B1.1a allele; and haplotype III carrying Lpx-B1.2 and the Lpx-B1.1c allele. Determination of Lpx-B1 transcript abundance and total LOX activity in mature grains revealed differences among these three haplotypes: haplotypes I, II and III showed high, intermediate and low levels, respectively, of functional Lpx-B1 transcripts and enzymatic activity.


CONCLUSIONS
In this germplasm collection, the Lpx-B1 gene family accounts for most of the total LOX activity in the mature grains. Information on these Lpx-B1 haplotypes provides significant improvement for prediction of LOX-1 activity levels in mature grains, and will therefore help in breeding programmes aimed at selection of new durum wheat genotypes with higher carotenoid contents in their end products.
CRA-Cereal Research Centre, S.S. 16, Km 675 - 71122 Foggia, Italy.
Angelo
A
Verlotta
Vanessa
V
De Simone
Anna M
AM
Mastrangelo
Luigi
L
Cattivelli
Roberto
R
Papa
Daniela
D
Trono
D000483:Alleles; D000595:Amino Acid Sequence; D001483:Base Sequence; D055162:Biocatalysis; D002338:Carotenoids / Q000378:metabolism*; D002874:Chromosome Mapping; D032461:Chromosomes, Plant / Q000235:genetics; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D018744:DNA, Plant / Q000737:chemistry / Q000235:genetics; D002523:Edible Grain / Q000235:genetics / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D005838:Genotype; D006239:Haplotypes; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D008084:Lipoxygenase / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D014908:Triticum / Q000201:enzymology / Q000235:genetics*; D019207:beta Carotene / Q000378:metabolism
D018076:DNA, Complementary; D018744:DNA, Plant; D007527:Isoenzymes; D010940:Plant Proteins; D019207:beta Carotene; D002338:Carotenoids; D008084:Lipoxygenase