Effect of light and protein synthesis inhibitors on gene expression of RubisCO and RubisCO subunit binding protein
Chen, G.Y.; Miao, Y.G.; Li, L.R.
Acta Phytophysiologica Sinica 19(3): 243-249
In leaves from rice plant grown for 7 days under light, no turnover of RubisCO was detected. But RubisCO subunit binding protein (rbcBP) turned over rapidly (Fig. 1). RubisCO protein synthesis in leaves was strongly stimulated by light. The amount of RubisCO in the leaves of etiolated seedlings increased rapidly during the first 24 h of illumination, then continued to increase slightly up to 72 h. However, the content of rbcBP in leaves only increased only within initial 6 h of illumination, then remained unchanged (Fig. 2). The transcription of small subunit of RubisCO (rbcS) gene in rice leaves was very sensitive to light (Fig. 3). The translatable mRNA of rbcS increased significantly during the first 36 h of illumination, then declined slightly but still remained at a high level. The translatable mRNA of large subunit of RubisCO (rbcL) did not increase until 12 h of illumination and began to decline to lower level after 36 h. The increase of transcription was detected after 24 h of illumination. The effect of protein synthesis inhibitors was also most significant on the transcription of rbcS gene as was that of light. Translatable mRNA for rbcS in rice leaves treated with cycloheximide declined by 80% after 30 min, it was more sensitive than those for rbcL and rbcBP (Fig. 4). The inhibition of chloramphenicol on transcription was similar to cycloheximide (Fig. 5). The translatable mRNA of rbcS decreased strikingly when the leaves were treated with chloramphenicol, but the translatable mRNA's of rbcL and rbcBP decreased to a lesser degree. These results showed that gene expression of rbcL, rbcS and rbcBP in rice leaves was affected differently by light and protein synthesis inhibitors at various levels of expression, and these effects were more sensitive at translation level. rbcS might play an important role in the regulation of gene expression.