Differential light regulated expression of nuclear genes encoding chloroplast and cytosolic glyceraldehyde-3-phosphate dehydrogenase in Nicotiana tabacum.

When tobacco (Nicotiana tabacum) plants were transferred from the dark to continuous white light, the steady-state mRNA levels transcribed from the nuclear genes encoding chloroplast (GapA and GapB) glyceraldehyde-3-phosphate dehydrogenase increased at least 30- to 50-fold, while the mRNA level for the cytosolic enzyme (GapC) increased only 10-fold. Kinetic analyses show that the rates of mRNA accumulation for GapA and GapB are identical reaching steady-state levels after 24-48 h in light. In contrast, mRNA accumulation for the GapC gene shows a completely different kinetic pattern, accumulating much faster than that of GapA and GapB. These results suggest that expression of GapC and GapA/B genes are controlled by different light regulated mechanisms and nuclear run-on analyses suggest that these effects are primarily due to increased transcription.