BIOGENESIS PATHWAY OF PINE CHLOROPLAST PROTEINS ENCODED IN THE NUCLEUS - IMPORT OF PINE PROTEINS INTO SPINACH-CHLOROPLASTS

Precursors to small subunits (SSU) of ribulose-1,5-bisphosphate carbox ylase/oxygenase (Rubisco, EC 4.1.1.39) and apoproteins of light-harves ting chlorophyll alb binding protein (LHCPII) in photosystem II were s ynthesized in vitro by expressing pine (Pinus thunbergii Parl.) cDNA c lones encoding these proteins. The precursors to pine SSU and LHCPII w ere post-translationally transported into spinach chloroplasts, proces sed into mature size, and localized in only stroma and thylakoid membr anes, respectively. The pine SSU was tightly integrated into spinach R ubisco; however, the pine LHCPII was not found in the light-harvesting chlorophyll-protein complex. These results suggest that a common biog enesis pathway of nuclear-encoded chloroplast proteins is present both in gymnosperms and in angiosperms.