Cloning and light-dependent expression of the gene coding for the P-protein of the glycine decarboxylase complex from peas.

The glycine decarboxylase multienzyme complex (EC 2.1.210) is located in the mitochondrial matrix and catalyzes a key reaction of the photorespiratory C-2 cycle of plants. The light-dependent control of the synthesis of the P-protein of this complex in pea (Pisum sativum cv. Alaska) leaves was studied using a partial (0.7 kb) cDNA clone. The size of the P-protein mRNA detected by this probe was 3.5 kb. When the mRNA hybrid selected by this probe was translated in vitro, a protein that migrated in sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) with an apparent molecular mass of 114 kDa was formed. This protein could be immunoprecipitated with the P-protein-specific antibody. The mass of the mature P-protein on SDS-PAGE is 100 kDa. This suggests the presence of a presequence used to direct the protein to the mitochondrial matrix. Analysis of the concentration of P-protein mRNA showed an approximately 5-fold increase in the abundance of this transcript in light-grown as compared to dark-grown pea seedlings. The time course for the production of P-protein mRNA following exposure of dark-grown peas to white light was compared to that for the H-protein of glycine decarboxylase, the small subunit of ribulose bisphosphate carboxylase/oxygenase. and the chlorophyll alb binding protein. All 4 mRNAs accumulated with similar kinetics where they remained low during the first 3 h of illumination, increased about 5-fold during the next 8 h. and then maintained a steady state over the next 12 h. [ABSTRACT FROM AUTHOR]