Functional Analysis of Pheophorbide a Oxygenase Gene and Its Promoter from Mango (Mangifera indica) Fruit

Abstract

Pheophorbide a oxygenase (PAO) is a key enzyme in the process of chlorophyll degradation. It can metabolize a produced in the process of chlorophyll degradation into red chlorophyll metabolite. The full-length cDNA sequence of PAO gene was cloned from “Gui fei” mango peels, the relative expression of three cultivars by RT-PCR was the highest in the green “Gui qi,” followed by the red “Gui fei” and the lowest in the yellow “Jin huang.” The analysis of carotenoid content in transgenic tomato fruit shows that overexpression of PAO can increase the content of β-carotene and inhibition of PAO gene expression can reduce the content of β-carotenein. Fragments of the 2.2 kb upstream region of the PAO gene were fused to the pGreenII 0800-Luc vector. We examined tobacco (Nicotiana tabacum) leaves carrying a series of nested PAO promoter – FLuc fusion for FLuc/RLuc activity. The region of −1218 to −3 in PAO promoter showed high activities in the three parts. Three 5’deletion analysis of the PAO promoter identified regions related to IAA-inducible and GA3-inducible expression as well as regions containing positive and negative elements. At low concentration, IAA was mainly negative regulation, GA3 was mainly positive regulation, and at high concentration, the results were opposite by measuring FLuc/RLuc activity. The study of PAO gene and promoter can provide some reference for us to regulate fruit color, especially the effect of the application of growth regulators on fruit color in mango production and cultivation.

Keywords

• Mango
• PAO
• chlorophyll degradation
• promoter
• content of β-carotene