Genotypic differences and glutathione metabolism response in wheat exposed to copper

In recent years, wheat (Triticum aestivum L.) yields have declined as a result of heavy metal pollution. In this study, hydroponics experiments were conducted to assess the genotypic differences in copper (Cu) tolerance and glutathione metabolism in wheat. Thirty-seven wheat cultivars from different primary cultivation areas in China were selected and exposed to Cu stress for 48 h. Six growth and physiological indexes in the young roots were measured, and a comprehensive evaluation of the resistance of wheat to Cu was achieved using correlation analysis, subordinate function analysis, and the median clustering method. Based on the average subordinate function values, the 37 wheat cultivars could be classified into a high Cu-resistant, medium Cu-resistant, and sensitive group. The root transcriptome of ‘Jimai 22’ (high Cu-resistant) and ‘Luomai 23’ (sensitive) under Cu stress was further sequenced using lllumina sequencing technology. The results showed that a total of 49,611 and 43,195 genes were discovered in Jimai 22 and Luomai 23, respectively, in response to Cu. Gene Ontology term enrichment combined with pathway analysis indicated that 26 overrepresented up-regulated DEGs were associated with glutathione metabolism in Jimai 22, while 17 DEGs associated with glutathione metabolism were identified in Luomai 23. Eight of the 13 unique DEGs in Jimai 22 encoded glutathione S-transferases (GST). In addition, the activity of enzymes, including glutathione reductase (GR), glutathione-S-transferase (GST) and ascorbate peroxidase (APX) were measured in the roots. Furthermore, the contents of ascorbate (ASC), reduced glutathione (GSH), oxidized glutathione (GSSG), and some nutrients, including Cu, potassium, calcium, magnesium, sodium, manganese, and zinc, were also determined. The results clearly indicated that excess Cu affected the concentrations of non-enzymatic antioxidants and nutrients (except for Cu). Besides that, APX activity in wheat was affected by excess Cu and it was higher in Jimai 22. On the contrary, GST and GR activity increased with Cu stress treatment for 48 h.