El pasado 05 de marzo estuvo con nosotros el Dr. Uchiumi Toshiki, de la Universidad de Kagoshima en Japón. Además de su agradable visita, también tuvimos la suerte de asistir a un seminario suyo titulado "Nitric Oxide and Plant Hemoglobins in Rhizobium-Legume Symbiosis", en el cual nos mostró una parte de los avances en este campo que hacen en su laboratorio.
Nitric oxide (NO) induces plant defense system and class 1 hemoglobins (Hb) control various physiological processes of plants by modulating NO level. Inoculation of symbiotic rhizobia specifically induced transient production of NO and expression of class 1 Hb genes in the roots of their host plants. In the root nodules, over-expression of class 1 Hb enhanced the fixation activity by reducing NO as an inhibitor of nitrogenase. An abscisic acid low-sensitive mutant of Lotus japonicus also showed the enhanced nitrogen fixation activity with reduced level of NO in the nodules. Furthermore, the quality and productivity of the seeds were also improved in this mutant. Plants recognize many molecules of bacteria like PAMPs (pathogen associated molecular patterns) and lipololysaccharides (LPS) of rhizobia are the candidates that induce NO in the host plants. However, the plant molecules involved in LPS recognition are not identified yet. The genes for LPS binding protein (LBP) were identified on the genome of L. japonicus and the function of LBP in the symbiosis will be discussed based on the recent results from transgenic hairy roots.