Recent studies have suggested that the genetic improvement could significantly enhance the cadmiun (Cd) accumulation, translocation and tolerance in plants. To date, there is no report on the use of transgenic techniques to enhance root-to-shoot Cd translocation and tolerance in tall fescue.  

The Molecular Breeding of Turfgrass and Forage Grass Group of Wuhan Botanical Garden isolated and functionally characterized a class II (CII) small heat shock proteins (sHSPs) gene, FaHSP17.8-CII in tall fescue.  

Results showed that when exposed to Cd stress, two FaHSP17.8-CII overexpressing lines (OE#3 and OE#7) exhibited 30% and 40% higher shoot fresh weight, and 31% and 40% higher root fresh weight, respectively than the wild type (WT). Likewise, the two OE lines showed lower electrolyte leakage and malondialdehyde than the WT plants. Together, these findings suggested that overexpression of FaHSP17.8-CII could enhance the Cd tolerance of grasses.   

Compared to the WT plants, the two OE lines had higher Cd concentration in their shoots and lower Cd concentration in the roots. Furthermore, overexpressing of FaHSP17.8-CII in tall fescue accelerated root-to-shoot Cd translocation and the translocation factor in two OE lines, which was 69% and 85% respectively greater than that in WT plants. All these findings suggested that the overexpressing of FaHSP17.8-CII facilitated Cd accumulation in shoots, probably by advancing the root-to-shoot translation of Cd.  

In Cd-stressed tall fescue, overexpressing of FaHSP17.8-CII enhanced Cd accumulation in shoots and photosystem II (PSII) activity, but reduced the reactive oxygen species (ROS) level.  

The study demonstrates that overexpressing FaHSP17.8-CII in tall fescue could improve Cd accumulation and tolerance simultaneously, and significantly increased root-to-shoot Cd translocation, indicating a higher Cd phytoremediation efficiency.  

This study entitled “Overexpression of FaHSP17.8-CII improves cadmium accumulation and tolerance in tall fescue shoots by promoting chloroplast stability and photosynthetic electron transfer of PSII” has been recently published in Journal of Hazardous Materials. 

Associate professor HU Tao from Wuhan Botanical Garden is the first author, and Professor CHEN Liang is the corresponding author. The study was supported by the National Natural Science Foundation of China and the Major Science and Technology Special Projects of Shandong Province. 

The FaHSP17.8-CII–PSII-ROS module responsible for enhanced Cd- translocation and tolerance in tall fescue (Image by WBG)