Abstract
It is of great importance to combine stress tolerance and plant quality for breeding research. In this study, the role of phytoene desaturase (PDS), ζ-carotene desaturase (ZDS) and carotene isomerase (CRTISO) in the carotenoid biosynthesis are correlated and compared. The three genes were derived from Lycium chinenses and involved in the desaturation of tetraterpene. Their over-expression significantly increased carotenoid accumulation and enhanced photosynthesis and salt tolerance in transgenic tobacco. Up-regulation of almost all the genes involved in the carotenoid biosynthesis pathway and only significant down-regulation of lycopene ε-cyclase (ε-LCY) gene were detected in those transgenic plants. Under salt stress, proline content, and activities of catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) were significantly increased, whereas malonaldehyde (MDA) and hydrogen peroxide (H2O2) accumulated less in the transgenic plants. The genes encoding ascorbate peroxidase (APX), CAT, POD, SOD, and pyrroline-5-carboxylate reductase (P5CR) were shown to responsive up-regulated significantly under the salt stress in the transgenic plants. This study indicated that LcPDS, LcZDS, and LcCRTISO have the potential to improve carotenoid content and salt tolerance in higher plant breeding.
Highlights
Carotenoids are a series of organic pigments, which spread widely in plants, animals, algae, some special fungi, and bacteria
The phylogenic trees demonstrated that LcPDS, LcZDS, and LcCRTISO coding protein were closely related to the corresponding genes in referenced species (Figure S5)
The overexpression of exogenous LcPDS, LcZDS, and LcCRTISO was found to have a significant impact on the homeostatic state of the carotenoid biosynthesis pathway in the transgenic tobacco and considered to contribute to the change of the phenotype
Summary
Carotenoids are a series of organic pigments, which spread widely in plants, animals, algae, some special fungi, and bacteria. To transform phytoene into lycopene, plants employ two desaturases, phytoene desaturase (PDS), forming 11 and 11' cis double bond, and z-carotene desaturase (ZDS), forming 7 and 7' cis double bond (Bartley et al, 1991; Araya-Garay et al, 2014). To fulfill the geometrical requirements of the desaturases, carotene isomerase (CRTISO) is employed to transform 9,15,9'-tricis-z-carotene into 9,9'-dicis-z-carotene, 7,9,9'-tricis-neurosporene into 9-cis-neurosporene and 7,9dicis-lycopene into all-trans-lycopene (Han et al, 2008; Yu et al, 2011). The reformed conjugated system, which contained eleven C-C double bonds in the tetraterpene skeleton, makes the molecules easier to absorb light energy and become excited (Hashimoto et al, 2018), and it is important for the functioning of carotenoids. Lycopene is transformed into its varieties containing cycle-, hydroxy-, and epoxidegroups, such as b-carotene, violaxanthin, zeaxanthin, lutein, and neoxanthin, etc. Lycopene is transformed into its varieties containing cycle-, hydroxy-, and epoxidegroups, such as b-carotene, violaxanthin, zeaxanthin, lutein, and neoxanthin, etc. under the catalyzation of lycopene bcyclase (b-LCY), e-cyclase (e-LCY), and b-carotene hydroxylase (b-CHY) (Bouvier et al, 2000; Kim and DellaPenna, 2006; Zhu et al, 2008)
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