C1 metabolism and the Calvin cycle function simultaneously and independently during HCHO metabolism and detoxification in Arabidopsis thaliana treated with HCHO solutions

Formaldehyde (HCHO) is suggested to be detoxified through one‐carbon (C1) metabolism or assimilated by the Calvin cycle in plants. To further understand the function of the Calvin cycle and C1 metabolism in HCHO metabolism in plants, HCHO elimination and metabolism by Arabidopsis thaliana in HCHO solutions was investigated in this study. Results verified that Arabidopsis could completely eliminate aqueous HCHO from the HCHO solutions. Carbon‐13 nuclear magnetic resonance (¹³C‐NMR) analysis showed that H¹³CHO absorbed by Arabidopsis was first oxidized to H¹³COOH. Subsequently, a clear increase in U‐¹³C]Gluc peaks accompanied by a strong enhancement in peaks of 2‐¹³C]Ser and 3‐¹³C]Ser appeared in Arabidopsis. Pretreatment with cyclosporin A or L‐carnitine, which might inhibit the transport of ¹³C‐enriched compounds into chloroplasts and mitochondria, caused a remarkable decline in yields of both U‐¹³C]Gluc and 3‐¹³C]Ser in H¹³CHO‐treated Arabidopsis. These results suggested that both the Calvin cycle and the C1 metabolism functioned simultaneously during HCHO detoxification. Moreover, both functioned more quickly under high H¹³CHO stress than low H¹³CHO stress. When a photorespiration mutant was treated in 6 mm H¹³CHO solution, formation of U‐¹³C]Gluc and 2‐¹³C]Ser was completely inhibited, but generation of 3‐¹³C]Ser was not significantly affected. This evidence suggested that the Calvin cycle and C1 metabolism functioned independently in Arabidopsis during HCHO metabolism.