Abstract:

The technique of reverse genetics such as anti-sense RNA has been used to down regulate gene expression of some important agronomic characters of crops. In this study anti-sense polyphenol oxidase (PPO) gene POT32 was transformed into potato (S. tuberosum L.) and the PPO effect on tuber browning in those transgenic potatoes was assessed. Potato tubers from twelve transgenic lines and the non-transformed control were analyzed for their PPO activity, phenolic substance content，browning index and browning intensity when the tubers were harvested and stored for 5 months respectively. The results showed that browning indexes of transgenic tubers were significantly lower than those of control. The PPO activity in transgenic tubers decreased by 26.01% to 48.65% compared with that in the control, and the content of phenolic substance decreased by 22.83% to 54.81%. The browning intensity of the transgenic line GD-9-qc-1 was 40.45% to 46.78% lower than that of the control. Although the browning could be observed in all transgenic lines when tubers were cut, the extent of browning was less and occurred much slower in most transgenic potato tubers than in control. The tuber browning index was 88.0% to 98.86% lower in transgenic lines than in control. The down regulation of the PPO gene also resulted in the decrease of the content of phenolic substance in transgenic potato tubers. Furthermore, the browning showed mainly in the vascular region of most of the transgenic tubers but in whole tuber cross section of the control. The down regulation of PPO gene performed well particularly in transgenic line GD-9-qc-1 and very little polyphenol oxidase was found in its tuber. The results above indicated that the anti-sense POT32 gene has suppressed or partially suppressed the expression of PPO gene in the transgenic potatoes.

Key words: Transgenic Potato, Anti-sense PPO Gene, Tuber-Browning