Abstract
CYTOCHROME P450s genes are a large gene family in the plant kingdom. Our earlier transcriptome data revealed that a CYTOCHROME P450 gene of Citrus sinensis (CsCYT75B1) was associated with flavonoid metabolism and was highly induced after drought stress. Here, we characterized the function of CsCYT75B1 in drought tolerance by overexpressing it in Arabidopsis thaliana. Our results demonstrated that the overexpression of the CsCYT75B1 gene significantly enhanced the total flavonoid contents with increased antioxidant activity in transgenic Arabidopsis. The gene expression results showed that several genes that are responsible for the biosynthesis of antioxidant flavonoids were induced by 2–12 fold in transgenic Arabidopsis lines. After 14 days of drought stress, all transgenic lines displayed an enhanced tolerance to drought stress along with accumulating antioxidant flavonoids with lower superoxide radicals and reactive oxygen species (ROS) than wild type plants. In addition, drought-stressed transgenic lines possessed higher antioxidant enzymatic activities than wild type transgenic lines. Moreover, the stressed transgenic lines had significantly lower levels of electrolytic leakage than wild type transgenic lines. These results demonstrate that the CsCYT75B1 gene of sweet orange functions in the metabolism of antioxidant flavonoid and contributes to drought tolerance by elevating ROS scavenging activities.
Highlights
The economically important and worldwide cultivated citrus fruits possesses abundant amounts of dietary flavonoids, vitamins, minerals, fibers, and folates
Table S2) which suggested that CYTOCHROME P450 75B1 gene expression pattern was correlated (Supplementary Figure S2) with metabolic data in Citrus sinensis (Supplementary Figure S1)
75B1 genes significantly accumulates antioxidant flavonoids with increased antioxidant activity and capacity in all transgenic lines; in addition, our gene expression results showed that several genes related to the accumulation of antioxidant flavonoids were up-regulated by 2–12 fold in transgenic lines
Summary
The economically important and worldwide cultivated citrus fruits possesses abundant amounts of dietary flavonoids, vitamins, minerals, fibers, and folates. Citrus fruits are mostly consumed freshly or as juice (sweet oranges) that becomes a direct source of nutritive metabolites [1]. Citrus plants are exposed to various abiotic stresses such as drought stress. Citrus plants biosynthesize some antioxidant flavonoids to cope against abnormal environmental conditions [2,3,4]. Flavonoid compounds are famous due to their high antioxidant activity that helps to detoxify the free radicals that are produced during drought stress. Citrus is a direct source of antioxidant flavonoids [6] that protects plants and boosts the human immune system
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