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Down-regulation of lycopene ε-cyclase expression in transgenic sweetpotato plants increases the carotenoid content and tolerance to abiotic stress

Ke, Qingbo, Kang, Le, Kim, Ho Soo, Xie, Tian, Liu, Chunjuan, Ji, Chang Yoon, Kim, Sun Ha, Park, Woo Sung, Ahn, Mi-Jeong, Wang, Shiwen, Li, Hongbing, Deng, Xiping, Kwak, Sang-Soo
Plant science 2019 v.281 pp. 52-60
9-cis-epoxycarotenoid dioxygenase, RNA interference, abscisic acid, beta-carotene, biosynthesis, callus, catalytic activity, chlorophyll, genes, humans, leaves, lutein, lycopene, lycopene epsilon-cyclase, membrane permeability, nutritive value, oxygen, photosystem II, salt stress, stress response, stress tolerance, sweet potatoes, transgenic plants, water stress
Carotenoids are required for many biological processes in plants and humans. Lycopene ε-cyclase (LCY-ε) catalyzes the conversion of lycopene into lutein via the α-branch carotenoid biosynthesis pathway. Down-regulation of IbLCY-ε by RNAi increases carotenoid accumulation and salt stress tolerance in transgenic sweetpotato calli. As the role of IbLCY-ε in carotenoid biosynthesis and environmental stress responses in whole plants is poorly understood, transgenic sweetpotato (RLE plants) with reduced expression of IbLCY-ε were developed. RLE plants contained higher levels of total carotenoid and β-carotene, due to an elevated β-carotene/lutein ratio rather than increased de novo biosynthesis. RLE plants showed high reactive oxygen species/radical-scavenging activity. They also exhibited an enhanced tolerance of both salt and drought stress, which was associated with lower membrane permeability and a higher photosynthetic rate, respectively. Elevated carotenoid accumulation in RLE plants mitigated the reductions in leaf photosystem II efficiency and chlorophyll induced by abiotic stress. Expression of the carotenoid cleavage genes 9-cis-epoxycarotenoid dioxygenase, carotenoid cleavage dioxygenase 1 (CCD1) and CCD4 was higher in RLE plants, as was abscisic acid accumulation. IbLCY-ε silencing thus offers an effective approach for developing sweetpotato plants with increased tolerance to abiotic stress that will grow on global marginal lands with no reduction in nutritional value.