Rice seedlings were transferred into a test tube containing rice growth medium without nitrogen
and grown at 25 °C under a light–dark cycle (16 h of light followed by 8 h of dark). Rice plant materials were
sampled at various times, from 1 to 7 days after inoculation. Symbiotic colonization of the GUS-tagged bacteria
within the rice plant tissues was examined by histochemical staining (Manassila et al. 2007).