Abstract
Leguminous plants form nodules where establish symbiotic nitrogen fixation with mycrosymbionts, rhizobia. Nitroge fixation requires huge amount of energy, which generated from the photosynthetic products supplied by host plants to rhizobia. Leghemoglobin (Lb) exists in root nodules exclusively and creates microaerobic condition for nitrogenase activity. Lb can be exist three different oxygenized state, Lb2+, Lb3+, and Lb4+, and Lb2+ expected to be dominant in nodules. Lb2+ releases oxygen for rhizobia and changes to Lb3+. Lb3+ should be reduced before re-associate with oxygen. In this hemoglobin recycle system, hemoglobin reductase plays an important role and will effect on symbiotic nitrogen fixation activity. We investigated the expression of gene of hemoglobin reductase in the symbiosis between Lotus japonicus and Mesorhizobium loti.
