Roles of RbcX in carboxysome biosynthesis in the cyanobacterium Synechococcus elongates PCC 7942  (Plant Physiol)

Introduction of the cyanobacterial carboxysome into C₃ crops represents a viable strategy to increase photosynthetic conversion efficiency and boost crop yield.  Key to this challenge is gaining a full understanding of the carboxysome system in cyanobacteria, including how these microcompartments assemble and function. In this manuscript, Huang et al investigated the role of RbcX, one of the chaperones of rubisco.  The authors demonstrated that RbcX was not required for the assembly of rubisco, and surprisingly that rbcX deletion mutants of Synechococcus elongatus PCC 7942 accumulated more, rather than less rubisco.  Furthermore, RbcX predominantly co-localised with rubisco inside both mature and newly synthesised carboxysomes, while rbcX mutants had fewer carboxysomes per cell.  These data indicate that RbcX may serve a crucial role in carboxysome assembly and stability, and will certainly inform future efforts to engineer carboxysomes into C₃ crops.  (Summary by Mike Page) Plant Physiol 10.1104/pp.18.01217