Characterization and mapping of durum wheat lipoxygenases

INGRID GARBUS; SORESI DANIELA; JOSÉ ROMERO; CARRERA ALICIA; VIVIANA ECHENIQUE

Mexico DF

Workshop; ITMI Workshop; 2011

CIMMYT

Durum wheat (Triticum turgidum L. ssp. durum, genomes AABB) constitutes the cereal of preference for semolina and pasta production. A bright yellow color is an important quality criterion for pasta making. Yellow color depends on the amount of carotenoid pigments in grain, which is the result of the balance between pigment synthesis and degradation, mainly by lipoxygenases (LPX). The number and location of lipoxygenases genes in durum wheat (Triticum turgidum L. ssp. durum) genome is not completely understood. Our laboratory recently reported the existence of a duplication at the Lpx-B1 locus (Lpx-B1.1 and Lpx-B1.2), mapped on chromosome 4B, and associated the deletion of the Lpx-B1.1 copy, with a reduction in lipoxygenase activity. A second lipoxygenase locus, Lpx-A3, associated with better semolina and pasta color was mapped on the homoeologous region on chromosome 4A. Here we focused on the physical organization of Lpx loci in chromosome 4A, where was identified a partially deleted copy of Lpx-1, called Lpx-A1_like. This copy colocalized within a 42 kbp region with Lpx-A3. The analysis of the sequences amplified with Lpx-A1_like based specific primers from the variety Kofa and the line UC1113 revealed the presence of two different deleted copies in UC1113 whereas only one was detected in Kofa, as was reported for Lpx-B1. This polymorphism was amplified in the available RIL population UC1113 x Kofa, to further map Lpx-A1_like in chromosome 4A short arm, between the microsatellite gwm192b and the locus Lpx-A3, thus confirming that in both genomes these two genes are close to each other. Finally, the Lpx1 locus was amplified from the variety Urartu, the ancestral donor of durum wheat genome A, being identified a unique functional copy comprised between exon 2 and exon 8. This finding suggests that both the deletion and the duplication identified in durum wheat genome A were not inherited from the ancestor. The knowledge of the physical location and structure of  Lp x genes is important to understand the on evolution of this family but also has practical implications for breeding since closely linked genes are difficult to separate by recombination.