The signal network of ascorbate homeostasis.

Ascorbate is a crucial antioxidant for scavenging hydrogen peroxide generated from the physiological processes and environmental stresses. Besides, the endo/exogenous factors that influence ascorbate level, our knowledge of the methanol stimulation is relatively less. Methanol, a byproduct from the demethylation of pectin during the enlargement of plant cell, is effective in enhancing the expression of ascorbate-biosynthetic genes of the Smirnoff-Wheeler and galacturonate (GalUA) pathways. In our previous work, hydrogen peroxide is a product of methanol detoxification through alcohol oxidase and NADPH oxidase activation, and acts as a secondary messenger for the activation of ascorbate-related genes. In this addendum, we propose a working model of the signaling network for ascorbate homeostasis in association with the apoplastic factors, such as methanol and oligogalacturonide during the growth and development of plant cell.