Tangerine tomato roots show increased accumulation of acyclic carotenoids, less abscisic acid, drought sensitivity, and impaired endomycorrhizal colonization. (August 2022) - Nayak, Jwalit J.
Abstract: 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 ( tang mic ) tomato and how this affects root to shoot biomass, mycorrhizal colonization, abscisic acid accumulation, and responses to drought. tang mic 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 tang mic relative to WT. The roots of tang mic hyperaccumulated acyclic cis -carotenes, while only trace levels of xanthophylls and abscisic acid were detected. In response to a water deficit, leaves from the tang mic 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 tang mic roots reduced abscisic acid levels, thereby likely impairing endomycorrhizal colonisation and drought-induced root to shoot signalling. Highlights: Photoisomerization of tetra- cis- lycopene is rate-limited in root-derived plastids. Tangerine tomato roots hyperaccumulate acyclic cis- carotenes and lack abscisic acid. Tangerine tomato roots show impaired endomycorrhizal colonization. Tangerine tomato plants show altered sensitivity to drought stress. Carotenoid isomerisation regulates root to shoot signalling and agronomic traits.