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β‐Carboxysomal proteins assemble into highly organized structures in Nicotiana chloroplasts
Author(s) -
Lin Myat T.,
Occhialini Alessandro,
Andralojc P. John,
Devonshire Jean,
Hines Kevin M.,
Parry Martin A. J.,
Hanson Maureen R.
Publication year - 2014
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.12536
Subject(s) - rubisco , chloroplast , photosynthesis , photorespiration , biochemistry , biology , cyanobacteria , nicotiana benthamiana , compartmentalization (fire protection) , microbiology and biotechnology , chemistry , biophysics , gene , genetics , bacteria , enzyme
Summary The photosynthetic efficiency of C 3 plants suffers from the reaction of ribulose 1,5‐bisphosphate carboxylase/oxygenase ( R ubisco) with O 2 instead of CO 2 , leading to the costly process of photorespiration. Increasing the concentration of CO 2 around R ubisco is a strategy used by photosynthetic prokaryotes such as cyanobacteria for more efficient incorporation of inorganic carbon. Engineering the cyanobacterial CO 2 ‐concentrating mechanism, the carboxysome, into chloroplasts is an approach to enhance photosynthesis or to compartmentalize other biochemical reactions to confer new capabilities on transgenic plants. We have chosen to explore the possibility of producing β‐carboxysomes from Synechococcus elongatu s PCC 7942, a model freshwater cyanobacterium. Using the agroinfiltration technique, we have transiently expressed multiple β‐carboxysomal proteins (CcmK2, CcmM, CcmL, CcmO and CcmN) in Nicotiana benthamiana with fusions that target these proteins into chloroplasts, and that provide fluorescent labels for visualizing the resultant structures. By confocal and electron microscopic analysis, we have observed that the shell proteins of the β‐carboxysome are able to assemble in plant chloroplasts into highly organized assemblies resembling empty microcompartments. We demonstrate that a foreign protein can be targeted with a 17‐amino‐acid CcmN peptide to the shell proteins inside chloroplasts. Our experiments establish the feasibility of introducing carboxysomes into chloroplasts for the potential compartmentalization of R ubisco or other proteins.