The Hidden Face of Rubisco

Area of Science:

• Plant biochemistry
• Molecular evolution
• Photosynthesis research

Background:

• Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is crucial for carbon fixation, comprising large (RbcL) and small (RbcS) subunits.
• Recent findings highlight novel RbcS variants with distinct biochemical properties and tissue-specific expression patterns.

Purpose of the Study:

• To investigate the characteristics and evolutionary significance of unusual RbcS variants found in plant trichomes.
• To understand the implications of these RbcS variants for Rubisco's catalytic efficiency and CO2 affinity.

Main Methods:

• Phylogenetic analysis of RbcS sequences.
• Biochemical characterization of Rubisco activity in relation to CO2 concentration and pH.
• Comparative analysis of RbcS expression in different plant tissues.

Main Results:

• Identified a distinct cluster of RbcS (cluster T) in trichomes, phylogenetically distant from mesophyll/bundle-sheath RbcS (cluster M).
• Rubisco with cluster T RbcS exhibits higher catalytic rates, lower CO2 affinity, and an acidic pH optimum.
• These properties suggest adaptation to high CO2 conditions, potentially for CO2 recycling.

Conclusions:

• Cluster T RbcS represents an ancient lineage, found across diverse plant phyla including pteridophytes and bryophytes.
• These findings reveal novel adaptations in Rubisco function and evolution, particularly in specialized plant tissues.