Carbon monoxide (CO) has been shown to regulate some biological processes in animals such as vasomotion, respiratory regulation and thermoregulation. It has also been implicated as a messenger molecule involved in intercellular neuronal communications. CO shares some biological properties of nitric oxide (NO), which has been shown to regulate a wide array of plant physiological responses including regulation of nutrient metabolism. The roles played by CO in nutrient stress responses in plants, however, remain largely unknown. Now, researchers at the Nanjing Agricultural University in China showed that CO can regulate iron-homeostasis in iron-starved Arabidopsis.

The researchers found that exogenous application of CO prevented chlorosis in iron-deficient Arabidopsis and Chlamydomonas. Endogenous level of CO was increased in Arabidopsis under iron deficiency. The compound was also found to regulate the expression of genes related to iron acquisition, specifically IRT1, FRO2, FIT1 and FER1. FRO2 and FER1 respectively codes for ferric reductase, which is required for plant acquisition of iron at low level in soils, and ferritin, a protein that stores iron.

CO treatment of maize mutants with defective iron intake resulted to restoration of greening in leaves. In addition, the team found evidences suggesting cross-talks between CO and NO in low iron conditions.

The published paper by the Plant Biotechnology Journal  available at  http://dx.doi.org/10.1111/j.1467-7652.2009.00469.x