Subambient growth CO2 leads to increased Rubisco small subunit gene expression in developing rice leaves

To test the hypothesis whether low atmospheric [CO2] can cause an increase of Rubisco small subunit gene expression, rice (Oryza sativa L.) growing un der ambient [CO2] at 350 mu mol mol(-1) was switched to subambient [CO2] at 175 mu molmol(-1) during late vegetative stage. After the switch, photosyn thesis rate of developing leaves initially declined but partially recovered after 8 days. Transcript levels of the Rubisco small subunit gene (rbcS) i n developing leaves increased within three days to almost twice that of amb ient-CO2 controls, followed later by an up-regulation of Rubisco total acti vity and protein content.