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

Abstract

The glycine decarboxylase multienzyme complex (EC 2.1.2.10) 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 a/b 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.