Pi Uptake and Translocation are affected in OEmiR399 transgenic Arabidopsis plants under freezing stress
To verify the role of tae-miR399 in the regulation of phosphorus homeostasis in Arabidopsis under freezing stress, we determined the total phosphorus and inorganic phosphorus (Pi) content of all Arabidopsis lines. The results showed at 24°C, there was no significant difference in the total phosphorus content of all Arabidopsis lines, while the Pi content of OEmiR399 transgenic Arabidopsis plants was significantly higher than that of WT (Fig. 8A and B). At 4°C, the total phosphorus content of OEmiR399 transgenic Arabidopsis plants increased significantly and was significantly higher than that of WT, but Pi content of OEmiR399 transgenic Arabidopsis plants was lower than that of WT (Fig. 8A and B). At -10℃, the total phosphorus content of OEmiR399 transgenic Arabidopsis plants decreased, and there was no significant difference in the total phosphorus content among all Arabidopsis lines, while the Pi content of OEmiR399 transgenic Arabidopsis plants was still significantly lower than that of WT ( Fig. 8A and B).
In the past few decades, the molecular mechanisms of Pi sensing and signal transduction in plants have been well confirmed. It is known that Pi transporters play a key role in Pi uptake and transport (Chiou & Lin, 2011; Liang, Wang, Zhao, Tian, & Liao, 2014). In order to verify whether the change in the phosphorus content of OEmiR399 transgenic Arabidopsis was due to the promotion of Pi transport, we performed the expression of the main phosphorus transporters genes (AtPHO1 ,AtPHT1;1 , AtPHT1;2 , and AtPHT1;4 ) of Arabidopsis. These results showed that the expression of AtPHO1 in WT gradually increased with the decrease of temperature,while the expression of AtPHO1 in in the OEmiR399 Arabidopsis plants was significantly lower than that of WT under low temperature stress (Fig. 8C). Under low temperature stress, the expression of AtPHT1s in all Arabidopsis gradually increasd. Obviously, at 4℃, the expressions of AtPHT1;1and AtPHT1;4 in the OEmiR399 Arabidopsis plants were higher than those in WT(Fig. 8D and F). And at -10℃, only the expression ofAtPHT1;4 in OEmiR399 Arabidopsis plants was significantly higher than that in WT (Fig. 8F). Although the expression of AtPHT1;2was induced at low temperature, there was no significant difference in its expression among all Arabidopsis lines (Fig. 8E).