Insight into durum wheat Lpx-B1: a small gene family coding for the lipoxygenase responsible for carotenoid bleaching in mature grains

Angelo Verlotta,Vanessa De Simone,Daniela Trono,Luigi Cattivelli,Anna M Mastrangelo,Roberto Papa

doi:10.1186/1471-2229-10-263

Abstract

BackgroundThe 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.ResultsIn 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.ConclusionsIn 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.

Highlights

The yellow colour of pasta products is one of the main criteria used by consumers to assess pasta quality
Identification and characterisation of genes and alleles at the Lpx-B1 locus of durum wheat To gain further insight into the organisation of the LpxB1 locus, we investigated whether this locus includes genes and/or alleles other than those already identified, and evaluated the consequent distribution in a large durum wheat germplasm collection
We report the characterisation of the small LpxB1 gene family identified in a large durum wheat germplasm collection, and relate the distribution and expression levels of the Lpx-B1 genes and alleles to the variations in LOX activity in mature grains

Summary

Introduction

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. The yellow colour is an important parameter in the definition of pasta quality, and it is a target for durum wheat (Triticum durum Desf.) breeding. This character arises from carotenoid pigments in semolina, which are mainly free and esterified lutein. Radicals produced during the intermediate states of linoleate hydroperoxidation can cause oxidation of carotenoid pigments, and a loss of the yellow colour in pasta products [5]

Methods

Results

Discussion

Conclusion