'ACTIVATOR' AND 'INHIBITOR' LEADING TO GENERATION AND STABILIZATION OF SYMBIOTIC ORGAN DEVELOPMENT IN LEGUME

摘要

Nodule is a symbiotic nitrogen fixation organ generated by biological interactions. The symbiotic organ is induced by Nod factor (lipochitin-oligosaccharides) derived from rhizobia and the excessive nodulation is suppressed by a long-distance signal (autoregulation signal) produced in shoots, on receiving the root-derived factor. These positive and negative regulators significantly contribute to generation and stabilization of the symbiotic organ development. Here I point out that Nod factor and HARl-mediated long-distance signal may correspond to "Activator" and "Inhibitor" in reaction diffusion (RD) system respectively that has been proposed by Alan Turing in 1952. The RD system consists of short distance "Activator" and long range "Inhibitor", and pattern formation starting from initially homogenous conditions is generated by local self-enhancement of "Activator", coupled with a long-range antagonistic effect by "Inhibitor". Trough pointing out the similarity between RD system and systemic regulation of symbiotic organ development, I will focus on the structural originality of Nod factor as a presumptive "Activator".