**5.1 A citrus cytochrome P450 gene,** *CsCYT75B1* **helping to induce drought tolerance by antioxidant Flavonoid accumulation**

Cytochrome P450 gene present in *Citrus sinensis* (*CsCYT75B1*) is linked with flavonoid metabolism and reported to be notably induced after drought stress. *CsCYT75B1* gene when overexpressed in *A. thaliana* significantly increased total flavonoid content. It also enhanced antioxidant activity in the transgenic Arabidopsis plant. Diverse genes responsible for flavonoids biosynthesis showed increased induction (2–12 folds) as a result of *CsCYT75B1* gene overexpression in these transgenic Arabidopsis lines. After induction of draught stress, these plants showed enhanced drought tolerance along with antioxidant flavonoids accumulation, lower level of ROS and superoxide radicals when compared to wild type plants. These transgenic lines also exhibited significantly lower levels of electrolytic leakage than wild types [131].
