Abstract
Arabidopsis thaliana crumpled leaf (crl) mutants have yellowish green and crumpled leaves, and contain fewer and giant chloroplasts. The CRL gene encodes a novel outer envelope membrane protein of plastids (Asano et al 2004). A. thaliana has a single AtCRL gene whereas the moss Physcomitrella patens has three CRL genes (PpCRL1, PpCRL2, PpCRL3). PpCRL3 seems to be a pseudo gene because of some fatal mutations. In this study, we analyzed the CRL homologous genes of P. patens by targeted gene disruption. First, we obtained some single gene disruptants for each CRL gene. They exhibited similar phenotypes of the wild type. Next, we isolated two lines as the PpCRL1 and 2 double knockout mutant. Both of them showed growth retardation and their cells contain fewer and larger chloroplasts comparing to the wild type. Moreover, AtCRL gene was transferred into the mutant moss. This complementation test showed that some lines display the wild-type phenotype in terms of plant size and chloroplast number and size. These results indicate that CRLs in P. patens play a critical role in determining plant size and chloroplast size similar to CRL in A. thaliana.
