Cytoplasmic glucose-6-phosphate dehydrogenase plays an important role in the silicon-enhanced alkaline tolerance in highland barley.

Glucose-6-phosphate dehydrogenase (G6PDH), as a key enzyme in the pentose phosphate pathway, extensively responds to the biotic and abiotic stresses. In this study we focussed on the G6PDH role in the alleviation of alkaline stress induced by silicon (Si) in highland barley. Application of Si reduced the water loss and malondialdehyde (MDA) and reactive oxygen species (ROS) contents, improved the fresh weight, photosynthesis, K+ content, and the superoxide dismutase (SOD) and catalase (CAT) activities, thus alleviating the damage caused by alkaline stress. The G6PDH activity, especially the cytoplasmic G6PDH, significantly increased under alkaline stress, and was further stimulated by the addition of exogenous Si. Meanwhile, the levels of NADPH and reduced glutathione (GSH) showed similar profiles to G6PDH activity under NaHCO3 and NaHCO3 + Si treatments. The inhibition of G6PDH activity by glucosamine abolished the relieving effect of Si on alkaline stress, which was manifested in the increase of ROS and the decrease of GSH content. Together, our results suggest that Si-enhanced tolerance of alkaline stress may be related to the regulation of GSH levels by the cytoplasmic G6PDH in highland barley.