期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：11
页码：3564-3569
DOI：10.1073/pnas.1420536112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceUsing a translational photosynthesis approach, we successfully increased CO2-assimilation in leaf chloroplasts of the model plant tobacco. Phylogenetic analysis revealed parallel evolutionary linkages between the large (L-) subunit of the CO2-fixing enzyme Rubisco and its molecular chaperone Rubisco accumulation factor 1 (RAF1). We experimentally tested and exploited this correlation using plastome transformation, producing plants that demonstrated the role of RAF1 in L-subunit assembly and resolve the RAF1 quaternary structure as a dimer. We show the increase in Rubisco biogenesis translated to improvements in leaf photosynthesis and growth of the plants. The outcomes have application to the growing interest into identifying and implementing strategies to supercharge photosynthesis to improve crop productivity and stem global food-security concerns. Enabling improvements to crop yield and resource use by enhancing the catalysis of the photosynthetic CO2-fixing enzyme Rubisco has been a longstanding challenge. Efforts toward realization of this goal have been greatly assisted by advances in understanding the complexities of Rubisco's biogenesis in plastids and the development of tailored chloroplast transformation tools. Here we generate transplastomic tobacco genotypes expressing Arabidopsis Rubisco large subunits (AtL), both on their own (producing tobAtL plants) and with a cognate Rubisco accumulation factor 1 (AtRAF1) chaperone (producing tobAtL-R1 plants) that has undergone parallel functional coevolution with AtL. We show AtRAF1 assembles as a dimer and is produced in tobAtL-R1 and Arabidopsis leaves at 10-15 nmol AtRAF1 monomers per square meter. Consistent with a postchaperonin large (L)-subunit assembly role, the AtRAF1 facilitated two to threefold improvements in the amount and biogenesis rate of hybrid L8AS8t Rubisco [comprising AtL and tobacco small (S) subunits] in tobAtL-R1 leaves compared with tobAtL, despite >threefold lower steady-state Rubisco mRNA levels in tobAtL-R1. Accompanying twofold increases in photosynthetic CO2-assimilation rate and plant growth were measured for tobAtL-R1 lines. These findings highlight the importance of ancillary protein complementarity during Rubisco biogenesis in plastids, the possible constraints this has imposed on Rubisco adaptive evolution, and the likely need for such interaction specificity to be considered when optimizing recombinant Rubisco bioengineering in plants.
