4.3 Trehalose treatment affects PpINH1, leading to improved cold resistance in peaches
In most plants, the amount of endogenous trehalose is typically low, however, it is strongly induced by environmental stresses, including extreme temperatures, salinity, and drought. Therefore, endogenous trehalose may be involved not only in plant metabolism, but also in signaling pathways (Paul et al. 2008). Application of exogenous trehalose may induce plant signal molecules that modulate the expression of stress response genes, thereby improving crops’ resistance to stresses (Kosar et al. 2019). Kosar et al. (2019) have reported that the application of exogenous trehalose improves the cold resistance of crops and harvested fruits, and Ding & Wang (2018) report that 10% trehalose treatment enhances the cold tolerance of fresh-cut pepper fruits by enhancing antioxidant activity and reducing cell ultrastructure injury. The mechanisms of these affects however, have not yet been reported. In this study, application of 1% trehalose to peaches in cold storage resulted in significantly enhanced PpINH1 expression, reduced VIN activity, and higher sucrose content, ultimately alleviating CI symptoms (Figure 6 ). These results suggest that up-regulated INHs inhibit VIN activity at the post-translational level in peach fruit.
Like overexpression of PpINH1 inhibiting the VIN in peaches (Figure 4 ), overexpression of StInvInh2A andStInvInh2B inhibits StvacINV1 in stored tubers, alleviating cold-induced sweetening and the resulting deterioration of quality (Liu et al., 2013). Similarly, when RNAi technology was used to silence the expression of the soybean invertase inhibitor GmCIF1 in transgenic plants, CWI activity increased significantly. These results suggest that VIN activity may be negatively regulated by INHs in plants (Tang et al., 2017).
Based on our findings we suggest that upregulated the expression ofPpINH1 results in the decreased VIN activity, increased sucrose content, and ultimately enhanced chilling resistance (Figure 7 ). This provides insight into the mechanism of enhancing chilling resistance by trehalose treatment.