title: Elucidating the genetic basis of antioxidant status in lettuce (Lactuca sativa).
abstract: A diet rich in phytonutrients from fruit and vegetables has been acknowledged to afford protection against a range of human diseases, but many of the most popular vegetables are low in phytonutrients. Wild relatives of crops may contain allelic variation for genes determining the concentrations of these beneficial phytonutrients, and therefore understanding the genetic basis of this variation is important for breeding efforts to enhance nutritional quality. In this study, lettuce recombinant inbred lines, generated from a cross between wild and cultivated lettuce (Lactuca serriola and Lactuca sativa, respectively), were analysed for antioxidant (AO) potential and important phytonutrients including carotenoids, chlorophyll and phenolic compounds. When grown in two environments, 96 quantitative trait loci (QTL) were identified for these nutritional traits: 4 for AO potential, 2 for carotenoid content, 3 for total chlorophyll content and 87 for individual phenolic compounds (two per compound on average). Most often, the L. serriola alleles conferred an increase in total AOs and metabolites. Candidate genes underlying these QTL were identified by BLASTn searches; in several cases, these had functions suggesting involvement in phytonutrient biosynthetic pathways. Analysis of a QTL on linkage group 3, which accounted for >30% of the variation in AO potential, revealed several candidate genes encoding multiple MYB transcription factors which regulate flavonoid biosynthesis and flavanone 3-hydroxylase, an enzyme involved in the biosynthesis of the flavonoids quercetin and kaempferol, which are known to have powerful AO activity. Follow-up quantitative RT-PCR of these candidates revealed that 5 out of 10 genes investigated were significantly differentially expressed between the wild and cultivated parents, providing further evidence of their potential involvement in determining the contrasting phenotypes. These results offer exciting opportunities to improve the nutritional content and health benefits of lettuce through marker-assisted breeding.
authors.affiliation: Centre for Biological Sciences, University of Southampton, Life Sciences , University Road, Southampton SO17 1BJ, UK.
authors.forename: Annabelle
authors.initials: A
authors.lastname: Damerum
authors.affiliation: Centre for Biological Sciences, University of Southampton, Life Sciences , University Road, Southampton SO17 1BJ, UK.
authors.forename: Stacey L
authors.initials: SL
authors.lastname: Selmes
authors.affiliation: Centre for Biological Sciences, University of Southampton, Life Sciences , University Road, Southampton SO17 1BJ, UK.
authors.forename: Gaia F
authors.initials: GF
authors.lastname: Biggi
authors.affiliation: Centre for Biological Sciences, University of Southampton, Life Sciences , University Road, Southampton SO17 1BJ, UK ; Vitacress Limited , Lower Link Farm, St Mary Bourne, Andover, Hampshire SP11 6DB, UK.
authors.forename: Graham Jj
authors.initials: GJ
authors.lastname: Clarkson
authors.affiliation: Vitacress Limited , Lower Link Farm, St Mary Bourne, Andover, Hampshire SP11 6DB, UK.
authors.forename: Steve D
authors.initials: SD
authors.lastname: Rothwell
authors.affiliation: The Genome Centre and the Department of Plant Sciences, University of California , Davis, CA 95616, USA.
authors.forename: Maria José
authors.initials: MJ
authors.lastname: Truco
authors.affiliation: The Genome Centre and the Department of Plant Sciences, University of California , Davis, CA 95616, USA.
authors.forename: Richard W
authors.initials: RW
authors.lastname: Michelmore
authors.affiliation: The James Hutton Institute , Invergowrie, Dundee DD2 5DA, UK.
authors.forename: Robert D
authors.initials: RD
authors.lastname: Hancock
authors.affiliation: The James Hutton Institute , Invergowrie, Dundee DD2 5DA, UK.
authors.forename: Connie
authors.initials: C
authors.lastname: Shellcock
authors.affiliation: Centre for Biological Sciences, University of Southampton, Life Sciences , University Road, Southampton SO17 1BJ, UK.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Chapman
authors.affiliation: Centre for Biological Sciences, University of Southampton, Life Sciences , University Road, Southampton SO17 1BJ, UK.
authors.forename: Gail
authors.initials: G
authors.lastname: Taylor