Variability of Carotenoid Biosynthesis in Orange Colored Capsicum spp

Pepper, Capsicum spp., is a worldwide crop valued for heat, nutrition, and rich pigment content. Carotenoids, the largest group of plant pigments, function as antioxidants and as vitamin A precursors. The most abundant carotenoids in ripe pepper fruits are β-carotene, capsanthin, and capsorubin. In this study, the carotenoid composition of orange fruited Capsicum lines was defined along with the allelic variability of the biosynthetic enzymes. The carotenoid chemical profiles present in seven orange pepper varieties were determined using a novel UPLC method. The orange appearance of the fruit was due either to the accumulation of β-carotene, or in two cases, due to only the accumulation of red and yellow carotenoids. Four carotenoid biosynthetic genes, Psy, Lcyb, CrtZ-2, and Ccs were cloned and sequenced from these cultivars. This data tested the hypothesis that different alleles for specific carotenoid biosynthetic enzymes are associated with specific carotenoid profiles in orange peppers. While the coding regions within Psy and CrtZ-2 did not change in any of the lines, the genomic sequence contained introns not previously reported. Lcyb and Ccs contained no introns but did exhibit polymorphisms resulting in amino acid changes; a new Ccs variant was found. When selectively breeding for high provitamin A levels, phenotypic recurrent selection based on fruit color is not sufficient, carotenoid chemical composition should also be conducted. Based on these results, specific alleles are candidate molecular markers for selection of orange pepper lines with high β-carotene and therefore high pro-vitamin A levels.

The mapping of phytochrome genes and photomorphogenic mutants of tomato

The map positions of five previously described phytochrome genes have been determined in tomato (Lycopersicon esculentum Mill.) The position of the yg-2 gene on chromosome 12 has been confirmed and the classical map revised. The position of the phytochrome A (phy A)-deficient fri mutants has been refined by revising the classical map of chromosome 10. The position of the PhyA gene is indistinguishable from that of the fri locus. The putative phyB1-deficient tri mutants were mapped by classical and RFLP analysis to chromosome 1. The PhyB1 gene, as predicted, was located at the same position. Several mutants with the high pigment (hp) phenotype, which exaggerates phytochrome responses, have been reported. Allelism tests confirmed that the hp-2 mutant is not allelic to other previously described hp (proposed here to be called hp-1) mutants and a second stronger hp-2 allele (hp-2 ( j )) was identified. The hp-2 gene was mapped to the classical, as well as the RFLP, map of chromosome 1.

Amplification of Ac in tomato is correlated with high Ac transposition activity

We have assayed the transposition activity of the maize transposable element Ac in transgenic tomato plants that had a single copy of Ac. We found that Ac elements were in either a high or low activity state and that an Ac insertion could cycle from low to high activity within a generation. The different transposition activities were not simply due to the chromosomal position of the element, because the same Ac insertion had different levels of activity in sibling plants. Transposition activity was measured by two methods, one genetic and one physical; both assays gave similar results for each plant studied. Notably, plants with active Ac elements had progeny with amplified Ac copy number, while no amplification was detected in lines containing Ac in a low activity state. Analysis of lines with amplified elements revealed that the elements could be either clustered or dispersed. Our results were consistent with amplification being the result of transposition.