Chloroplast differentiation in angiosperm plants depends
on the light-dependent conversion of protochlorophyllide
to chlorophyllide by NADPH:protochlorophyllide
oxidoreductase (PORA; EC 1.6.99.1), a
nuclearly encoded protein. The protein import of the
precursor form of PORA into plastids was shown
previously to strictly depend on the presence of
its substrate protochlorophyllide. PORA seemed to
follow a novel, posttranslationally regulated import
route. Here we demonstrate that the precursor of
PORA from barley is imported into isolated barley
plastids independently of protochlorophyllide. PORA
as well as PORB import is competed for by the precursor
of the small subunit of Rubisco. The data demonstrate
that the PORA precursor uses the general
import pathway into plastids. Furthermore,
Print ISSN: 1431-6730
Volume: 381, 12/2000
Pages: 1263 - 1267