Aldehyde dehydrogenases and the hypothesis of a glycolaldehyde shunt pathway of photorespiration.

Aldehyde dehydrogenase enzymes (ALDHs) catalyse the oxidation of a broad range of aliphatic and aromatic aldehydes to their corresponding carboxylic acids using NAD+ or NADP+ as cofactors. In our article published in Scientific Reports, we demonstrated that mutations in Arabidopsis ALDH3I1 and ALDH7B4 genes altered the cellular contents of NAD(P)H, the total as well as the reduction state of glutathione; and decreased the efficiency of photosynthesis, thus placing ALDH activity as an important source of reducing power for cellular redox homeostasis. Our results also revealed that the ALDHs contribute to the reducing power required for the nitrate assimilation. Here, we discussed and elucidated the innovative hypothesis of the glycolaldehyde shunt pathway of photorespiration that would involve ALDHs generating in contrast to the known core photorespiration reactions, a net gain of two moles of NAD(P)H to support nitrate assimilation, glutathione homeostasis and ROS detoxification.