Suppression of the beta-carotene hydroxylase gene increases beta-carotene content and tolerance to abiotic stress in transgenic sweetpotato plants Le Kang

Abstract

beta-carotene, a carotenoid that plays a key photo-protective role in plants is converted into zeaxanthin by a beta-carotene hydroxylase (CHY-beta). Previous work showed that down-regulation of IbCHY-beta by RNA interference (RNAi) results in higher levels of beta-carotene and total carotenoids, as well as salt stress tolerance, in cultured transgenic sweetpotato cells. In this study, we introduced the RNAi-IbCHY-beta construct into a white-fleshed sweetpotato cultivar (cv. Yulmi) by Agrobacterium-mediated transformation. Among the 13 resultant transgenic sweetpotato plants (referred to as RC plants), three lines were selected for further characterization on the basis of IbCHY-beta transcript levels. The RC plants had orange flesh, total carotenoid and beta-carotene contents in storage roots were 2-fold and 16-fold higher, respectively, than those of non-transgenic (NT) plants. Unlike storage roots, total carotenoid and beta-carotene levels in the leaves of RC plants were slightly increased compared to NT plants. The leaves of RC plants also exhibited tolerance to methyl viologen (MV)-mediated oxidative stress, which was associated with higher 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical beta-scavenging activity. In addition, RC plants maintained higher levels of chlorophyll and higher photosystem II efficiency than NT plants after 250 mM NaCI stress. Yield of storage roots did not differ significantly between RC and NT plants. These observations suggest that RC plants might be useful as a nutritious and environmental stress -tolerant crop on marginal lands around the world. (C) 2017 Elsevier Masson SAS. All rights reserved.