Purification and use of carotenoid standards to quantify cis-trans geometrical carotenoid isomers in plant tissues.

Reverse-phase high-performance liquid chromatography (HPLC) is a preferred method used to identify and quantify carotenoids. Here, we describe a straightforward, reliable, and cost-effective protocol to purify and develop individual carotenoid standards for absolute quantification of carotenoids, including selected cis-trans (geometric) isomers. Analytical techniques to extract, purify and collect individual carotenoids using an HPLC system equipped with a Diode Array Detector (DAD) and fraction collector are described. Carotenoids were separated and identified by their characteristic ultraviolet-visible (UV-Vis) absorption spectra and individually isolated based on their retention times using a C30 column. This chapter outlines how to prepare standard calibration curves using known quantities of purified and/or commercially available carotenoids. A series of molar extinction and slope coefficients for phytoene, phytofluene, ζ-carotene, neurosporene, pro-lycopene, all trans-lycopene, lutein, ß-carotene, zeaxanthin, antheraxanthin, violaxanthin, neoxanthin, capsanthin, capsorubin and ß-cryptoxanthin are defined to enable absolute quantification of their abundance in plant, animal, and bacterial tissues. Different approaches for reporting carotenoid abundance by absolute concentration, relative composition, and/or using ratios of different pigments are provided as a convenient resource for carotenoid researchers.

Tangerine tomato roots show increased accumulation of acyclic carotenoids, less abscisic acid, drought sensitivity, and impaired endomycorrhizal colonization.

The Heirloom Golden tangerine tomato fruit variety is highly nutritious due to accumulation of tetra-cis-lycopene, that has a higher bioavailability and recognised health benefits in treating anti-inflammatory diseases compared to all-trans-lycopene isomers found in red tomatoes. We investigated if photoisomerization of tetra-cis-lycopene occurs in roots of the MicroTom tangerine (tangmic) tomato and how this affects root to shoot biomass, mycorrhizal colonization, abscisic acid accumulation, and responses to drought. tangmic plants grown in soil under glasshouse conditions displayed a reduction in height, number of flowers, fruit yield, and root length compared to wild-type (WT). Soil inoculation with Rhizophagus irregularis revealed fewer arbuscules and other fungal structures in the endodermal cells of roots in tangmic relative to WT. The roots of tangmic hyperaccumulated acyclic cis-carotenes, while only trace levels of xanthophylls and abscisic acid were detected. In response to a water deficit, leaves from the tangmic plants displayed a rapid decline in maximum quantum yield of photosystem II compared to WT, indicating a defective root to shoot signalling response to drought. The lack of xanthophylls biosynthesis in tangmic roots reduced abscisic acid levels, thereby likely impairing endomycorrhizal colonisation and drought-induced root to shoot signalling.