Effects of UVB radiation on protein turnover of Rubisco and LHCII in rice

Abstract

We previously found that the amount of Rubisco dramatically decreased in leaves of UV-sensitive rice grown with supplemental UVB radiation, while the amount of LHCII was not so much reduced [Hidema et al. 1996, Plant Cell Physiology.]. This work was aimed to clarify the effects of UVB radiation on synthesis and degradation of Rubisco and LHCII in leaves of UV-resistant Sasanishiki and UV-sensitive Norin 1 rice. And we examined the changes in the amounts of Rubisco or LHCII synthesized and degraded using 15N tracer, and mRNA transcription levels of rbcL, rbcS, and cab genes by RT-PCT analysis, during leaf development. The amount of Rubisco synthesized in Norin 1 grown under supplemental UVB radiation remarkably decreased during leaf developing, while the amount of LHCII synthesized in leaves of both cultivars was scarcely affected by supplemental UVB. The degradation of Rubisco and LHCII could not be detected during leaf development until leaf fully expanded in both plants grown with or without supplemental UVB, and started immediately after full expansion of leave. The mRNA transcripts for rbcS in Norin 1 greatly reduced by supplemental UVB. These results indicate that the synthesis of Rubisco was remarkably inhibited by UVB radiation during leaf development, and that the degradation of Rubisco was accelerated by UVB after leaf fully expanded.