Photosynthetic trichomes contain a specific Rubisco with a modified pH-dependent activity

Rubisco (Ribulose-1,5-biphosphate carboxylase/oxygenase) is the key enzyme in photosynthetic carbon fixation. In C₃ plants, the enzyme is usually found in mesophyll cells and guard cells, but it also can be found in photosynthetic glandular trichomes such as those found in tobacco. Laterre et al. used comparative proteomics to identify proteins specifically expressed in glandular trichomes. One of those they identified is a Rubisco small subunit protein, NtRbcS-T, which clusters with a distinct subset of RbcS subunits identified from other plants with secretory trichomes. Rubisco complexes incorporating the trichome subunits also show biochemical differences, including altered kinetics and pH dependency. The authors propose that this enzyme may be optimized for the distinctive cellular environment of glandular trichomes arising from the production of specialized metabolites. Plant Physiol. 10.​1104/​pp.​17.​00062