Expression of heterologous Vitreoscilla hemoglobin in barley

Anaerobiosis occurs in seeds of many higher plants during imbibition. After successful germination followed by penetration of the enclosing structures by the radicle, the embryo switches from fermentative to aerobic energy metabolism. The microbial population, which is naturally present on the covering layers of barley grains, may lead to oxygen deficiency by competing for oxygen with the grain tissues. Although imbibed barley grains can survive several days under anoxia, they require oxygen to complete germination. Therefore, novel methods are useful to improve oxygen transfer and enhance germination of seeds. The advances in genetic engineering have opened new possibilities to study oxygen limitation and other critical mechanisms of germination. Previously, heterologous expression of Vitreoscilla hemoglobin (VHb) has been shown to improve either growth properties or productivity of various microbes and plants. Therefore, our metabolic engineering approach was to express the Vitreoscilla hemoglobin gene (vhb) in germinating barley to alleviate adverse effects of inadequate oxygen availability. However, our results show that VHb expression did not improve germination or growth of barley.