The metabolic effects of native and transgenic hemoglobins on plants

The strictly aerobic bacterium Vitreoscilla expresses a hemoglobin-like pro tein, VHb, when subjected to oxygen stress. When expressed in plants, this has several intriguing physiological effects, such as improving the overall growth rate, speeding germination and flowering, and increasing the produc tivity of certain oxygen-requiring metabolic pathways. Although the mechani sms behind the effects of VHb in heterologous hosts are not yet fully chara cterized, it has been suggested that VHb facilitates oxygen transport and/o r storage. This hypothesis is supported by the kinetic properties of VHb, w hich allow very rapid dissociation of oxygen from the protein.