2005 Volume 22 Issue 1 Pages 39-45
The nonmevalonate pathway produces isopentenyl diphosphate (IPP) in plastids, as does the mevalonate pathway present in the cytosol in higher plants. IPP is a precursor of an abundant array of isoprenoids, including pigments essential for photosynthesis. Two high-chlorophyll-fluorescence mutants, isp1-1 and isp1-2, in which the ispD gene was partially inactivated, were characterzed. The ispD gene encodes 4-diphosphocytidyl-2-C-methyl-D-erythritol synthase, which functions in the third step of the nonmevalonate pathway in plastids. In mutant seedlings cultured at 50 µmol photons m−2 s−1, the photosynthetic electron transport activity and chlorophyll content were reduced. The phenotype was partially suppressed in seedlings cultured at a relatively high light intensity of 300 µmol photons m−2 s−1. These results suggest that the full activity of the nonmevalonate pathway is essential for photo-acclimation, particularly to low light conditions.