Department of Applied Biosciences, Graduate School of Life Sciences, Research Center for Life and Environmental Sciences, Toyo University, Japan

Biograph
Mikihisa UMEHARA is a Professor of Department of Applied Biosciences and Graduate School of Life Sciences, a Vice Director of Research Center for Life and Environmental Sciences, Toyo University, Japan. His major is plant physiology and plant biotechnology. He graduated from the University of Tsukuba in 1997, finished a doctor’s course at the Graduate School of Biological Sciences, the University of Tsukuba in 2004, and obtained Ph.D. in Science. He worked on onion breeding in Department of Biotechnology, Fukuoka Agricultural Research Center from 2004 to 2007. He joined RIKEN Plant Science Center as a special postdoctoral researcher in 2007 and worked on a class of plant hormones, strigolactones. In 2011, he moved to Toyo University as a associate professor, and became a full professor in 2015.

Speech Title: Relationships between endogenous phytohormone levels and adventitious shoot formation in ipecac

Abstract: Adventitious shoot formation is an important technique for the propagation of economically important crops and for the regeneration of transgenic plants. Phytohormone treatment is required for the induction of adventitious shoots in most species. Whether adventitious shoots can be induced is determined by the balance between auxin and cytokinin levels. Much effort goes into determining optimum concentrations and combinations of phytohormones in each tissue used as explants and in each plant species. In ipecac (Carapichea ipecacuanha (Brot.) L. Andersson), however, shoots form on internodal segments without phytohormone treatment. This creates an opportunity to analyze the dynamics of endogenous phytohormones during adventitious shoot formation. Adventitious shoots that formed in the apical region of internodal segments were derived from epidermal cells. One of the shoots grew vigorously with a vascular bundle connected to that of the segment, the others were suppressed the outgrowth. When the biggest shoot was cut out, other shoots start to grow up. By 1-Naphthalene acetic acid (NAA) treatment, other shoot growth was suppressed. This phenomenon is similar to the apical dominance. During adventitious shoot formation, endogenous auxin accumulated in the basal region of segments, while cytokinins accumulated in the middle region. Thus, the distribution of auxin, not cytokinins, determined where adventitious shoots formed.