Abstract:l103s was a rice ( Oryza sativa L. ) mutant whose leaves would mm into chimerical chlorophylldeficient when treated with varied temperature (high - low - high). The alteration of whole leaf protein was studied with two-dimensional electrophoresis during the bleaching process. No changes of large subunit and small subunit of Rubisco had been detected in the bleached tissues of 1103s, but a 51 kD (PI =-4.5) special polypeptide-P1 disappeared in the white area during the bleaching process. P1 polypeptide was also detected in those tissues which remained green on the chlorophyll deficient leaves, although its amount apparenfiy decreased. In the tissue of low-temperature treated 1103s and l103s × 8902s, the normal expression of P1 polypeptide had been detected. The data suggest that P1 is an important chlorophyll-synthesis related down stream functional protein. In 1103s, it is regulated by some yet-tmknown temperature-sensitive mechanisms.