Probing Cell Wall Structure in the Soybean Root Nodule

Abstract

The infection of soybean (Glycine max) by Bradyrhizobium japonicum has been observed to occur through root hairs. The region of the root just below the smallest emergent root hairs and just above the zone of rapid root elongation is most susceptible to nodulation by rhizobia (1). An early response of the host plant is the marked curling of the root hairs, accompanied by the induction of meristematic activity in the cortex of the root adjacent to the point of infection. The infection thread is initiated at, or near, the growing tip of a root hair following the entrapment of rhizobia in the crook of the curled root hair. The stimulation of plant cell division induces active cell wall synthesis, which in turn facilitates the growth of the infection thread. Thus, the interaction of rhizobia with the apparatus of plant cell wall synthesis may be very important in nodule initiation and development.