Nitric oxide and hydrogen peroxide increase glucose-6-phosphate dehydrogenase activities and expression upon drought stress in soybean roots

Key message Changes in glucose-6-phosphate dehydrogenase (G6PD) isoforms activities and expression were investigated in soybean roots under drought, suggesting that cytosolic G6PD plays a main role by regulating H 2 O 2 signal and redox homeostasis. Abstract G6PD acts a vital role in plant growth, development and stress adaptation. Drought (PEG6000 treatment) could markedly increase the enzymatic activities of cytosolic G6PD ( Cyt-G6PD ) and compartmented G6PD (mainly plastidic P2-G6PD) in soybean roots. Application of G6PD inhibitor upon drought condition dramatically decreased the intracellular NADPH and reduced glutathione levels in soybean roots. Nitric oxide (NO) and hydrogen peroxide (H 2 O 2 ) participated in the regulation of Cyt-G6PD and P2-G6PD enzymatic activities under drought stress. Diphenylene iodonium (DPI), an inhibitor of NADPH oxidase, abolished the drought-induced accumulation of H 2 O 2 . The exogenous application of H 2 O 2 and its production inhibitor (DPI) could stimulate and inhibit the NO accumulation, respectively, but not vice versa. qRT-PCR analysis confirmed that NO, as the downstream signal of H 2 O 2 , positively regulated the transcription of genes encoding Cyt-G6PD ( GPD5 , G6PD6 , G6PD7 ) under drought stress in soybean roots. Comparatively, NO and H 2 O 2 signals negatively regulated the gene expression of compartmented G6PD ( GPD1 , G6PD2 , G6PD4 ), indicating that a post-transcriptional mechanism was involved in compartmented G6PD regulation. Taken together, the high Cyt-G6PD activity is essential for maintaining redox homeostasis upon drought condition in soybean roots, and the H 2 O 2 -dependent NO cascade signal is differently involved in Cyt-G6PD and compartmented G6PD regulation.