Abstract: The potato (Solanum tuberosum L.) is the fourth food crop in the world. Low temperature storage regarding processing quality is the focus of post-harvesting physiology. In this experiment, a full cDNA sequence of vacuolar invertase inhibitor gene was amplified from leaves of tobacco T1 strain by RT-PCR using the primers designed on the base of published sequence of NCBI (Nt-VIF, GenBank assession number AY594179) and. Analysis of Blast showed that the cloned cDNA shares 100% homology with Nt-VIF of tobacco. The sense-orientation vector containing Nt-VIF cDNA regulated by 35S promoter was introduced successfully into potato cv. E-Potato 3 (E3) by the PCR detection and Northern and Southern blot analysis. The transgenic tubers were harvested and stored at 4℃ or 20℃ for 1 month in order to analyze the variation in reducing sugar (RS) content and vacuolar invertase (VI) activity. The results showed that VI activity was regulated by temperature, which was lower in high temperature than that in low temperature. There were no significant variances in VI activity between transgenic and non-transgenic (CK) tubers when they stored at high temperature, but VI activity of the transgenic tubers stored at low temperature was inhibited by a range of 22.7 (Line A-3) - 78.1% (Line A-31) comparing with CK. Correspondently, there were also no remarkable differences in RS content existed between transgenic and CK tubers at high temperature while the RS content of low temperature stored transgenic tubers decreased by 20 (Line A-17) to 80.5% (Line A-30). Further analysis revealed a significant linear relationship between IV activity and RS content of the transgenic tubers stored at low temperature which could be presented as RS = 0.289VI + 0.0736. Therefore, the present research approved that expression level of Nt-VIF was regulated by temperature and low temperature enhanced its expression which resulted in obvious inhibition of VI activity leading to a lower accumulation of RS in potato tubers. This implies a potential approach to slow RS accumulation of potato tubers during low temperature storage through regulating invertase activity.

Key words: Solanum tuberosum, Low temperature sweetening, Invertase inhibitor, Genetic modification