ACCLIMATION OF PHOTOSYNTHESIS TO ELEVATED CO2 THROUGH FEEDBACK-REGULATION OF GENE-EXPRESSION - CLIMATE OF OPINION

Although down-regulation of photosynthesis in higher C-3 plants expose d to long-term elevated CO2 has been recognized in plants with low sin k activity or poor nutrient status, the underlying molecular mechanism s remain unclear. This review covers aspects of rising CO2 on plant pr oductivity in general, and then focuses on photosynthesis, biochemistr y (stroma and thylakoid proteins, Rubisco activities and metabolites), and gene expression in tomato plants grown under ambient or elevated CO2. Taking into account these data and the recent discovery that gluc ose triggers repression of photosynthetic gene transcription, a molecu lar mechanism is proposed for feedback regulation of photosynthesis un der high CO2. Different living organisms such as bacteria, yeast, and mammals have been investigated for the sensing mechanisms of the carbo hydrate status of their cells, and this information is used together w ith some recent data obtained for plants to propose how hexose levels might be sensed in higher plant cells.