对刚收获和贮藏5个月后的12个转基因马铃薯品系及对照块茎进行褐化指标的生理检测，发现2个检测时期的各褐化指标在供试品系间差异均达到显著或极显著水平。综合2个检测时期并与对照相比，PPO活性降幅为26.01%~48.65%；酚物质含量降低22.83%~54.81%；褐化强度除GD-9-qc-1低于对照40.45%~46.78%外，其余品系高于对照或与对照无差别。切割块茎发现，大部分转基因品系较对照褐化出现晚，褐化程度低，褐化指数低于对照88.0%~98.86%。PPO的化学定位显示，低褐化转基因品系的多酚氧化酶集中于维管束环，含量明显少于对照，其中GD-9-qc-1仅有少量多酚氧化酶显现出来，推测是由于反义PPO基因抑制块茎POT32基因表达的结果。进一步的方差、相关分析表明，除对多酚氧化酶含量抑制外，反义PPO基因还降低酚物质含量以减轻块茎损伤褐化。
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.
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