The CRL plastid outer envelope protein supports TOC75-V / OEP80 complex formation in Arabidopsis

Embedded β-barrel proteins in the outer envelope membrane mediate most cellular traffic between the cytoplasm and the plastids. Although TOC75-V/OEP80 has been implicated in the insertion and assembly of β-barrel proteins in the outer envelope membrane of Arabidopsis thaliana , relatively little is known about this process. CRUMPLED LEAF ( CRL ) encodes a protein localizing in the outer envelope membrane, and its loss of function results in pleiotropic defects, including altered plant morphogenesis, growth retardation, suppression of plastid division, and spontaneous light intensity-dependent localized cell death. A suppressor screen conducted on mutagenized crl mutants with ethyl methanesulfonate revealed that a missense mutation in OEP80 suppresses crl ’s pleiotropic defects. Furthermore, we found that the complex formation of OEP80 was compromised in crl . Furthermore, we demonstrated that CRL interacts with OEP80 in vivo and that a portion of CRL is present in protein complexes with the same molecular weight as the OEP80-associated complex. Our results suggest that CRL interacts with OEP80 to regulate its complex formation. CRL has been shown to be involved in plastid protein import; therefore, pleiotropic defects in crl are likely due to the combined effects of decreased plastid protein import and altered membrane integration of β-barrel proteins in the outer envelope membrane. This study sheds light on the mechanisms that allow the integration of β-barrel proteins into the outer envelope membrane of plastids and the significance of this finding for plant cellular processes. ### Competing Interest Statement The authors have declared no competing interest.