Pollen Confers a Xenia Effect on Linalool Oxide Accumulation in Pummelo Fruit by Enhancing the Expression of a Cytochrome P450 78A7 Gene 1.

The aroma quality of citrus fruit is determined by volatiles that are present at extremely low levels in the citrus fruit juice sacs; it can be greatly improved by increasing volatiles. In this study, we showed that the contents of - and -linalool oxides were significantly increased in the juice sacs of three pummelos artificially pollinated with the (MS) pollen. A novel cytochrome P450 78A7 gene (1) was significantly upregulated in the juice sacs of Huanong Red pummelo pollinated with MS pollen in comparison to that with open pollination. Compared to wild-type tobacco Bright-Yellow2 cells, transgenic cells overexpressing 1 promoted a 3- to 4-fold more conversion of (-)-linalool to - and -linalool oxides. Overall, our results suggest that MS pollen has a xenia effect on pummelo fruit aroma quality, and 1 is a linalool oxide synthase gene that played an important role in the xenia effect.