Abstract
RuBisCO is the rate-limiting enzyme in CO2 assimilation, and is also a major nitrogen-containing component in plant leaves. Therefore, the quantitative regulation of RuBisCO (qrr) is an important mechanism for optimally control of photosynthesis and allocation of nitrogen in plants. In this study, we analyzed four qrr mutants which show low amount of RuBisCO from 11,000 EMS mutagenized seedlings of Arabidopsis thaliana. In qrr 3, 4, 5 and 7, rbcL and S mRNA accumulated as the level as that in wild type, showing that low amount of RuBisCO was not caused by a decreasing transcription rate. In immunoblot analysis, the accumulation rate of RuBisCO in qrr3 and qrr5 was much lower than in wild type, but not in qrr4. In contrast, qrr7 showed a decreasing accumulation rate in late stage of greening. We identified mutated genes of qrr 4 and 5 encoding different unknown protein with transit peptides for chloroplasts.
