A ground-breaking study led by Zhou and colleagues (2023) has made significant strides in enhancing the efficiency of the plant Rubisco, a crucial enzyme responsible for photosynthesis, by studying the carboxylation properties of a particular type of red algae. The findings could lead to significant improvements in plant growth, paving the way for potential agricultural innovations.
For years, scientists have aimed to enhance plant Rubisco’s carboxylation capabilities, hoping to mimic the more efficient version of the red algae Griffithsia monilis, known as GmRubisco. The researchers attempt to improve Rubisco has primarily involved unexpected amino acid substitutions away from the enzyme’s catalytic site, which, unfortunately, has often led to unpredictable results, thus hindering rational design attempts.
To address these challenges, Zhou et al. (2023) determined the crystal structure of GmRubisco to a resolution of 1.7 angstroms, identifying three structurally divergent domains relative to the red-type bacterial Rhodobacter sphaeroides Rubisco, referred to as RsRubisco. RsRubisco is distinct in that it can be expressed in Escherichia coli and plants, unlike its algal counterpart.
In a comparative kinetic study involving 11 RsRubisco chimeras, the research team discovered that incorporating specific amino acid substitutions—C329A and A332V—from the GmRubisco’s Loop 6 into RsRubisco resulted in substantial enhancements. The carboxylation rate increased by 60%, the carboxylation efficiency in air improved by 22%, and the specificity of the enzyme for CO2 over O2 rose by 7%.
Most significantly, when the team transformed this RsRubisco Loop 6 mutant into tobacco plants, they observed an enhancement in photosynthesis and growth up to twofold compared to tobacco plants producing the wild-type RsRubisco.
The findings from Zhou et al. demonstrate a promising direction for further research into improving Rubisco’s enzymatic potential. The team’s identifying and testing amino acid grafts from algal Rubisco offers a significant breakthrough in our understanding of Rubisco modification, paving the way towards increased plant productivity, with possible profound impacts on global food security and carbon sequestration efforts. However, it is essential to note that these are early-stage findings, and more research is needed before these techniques can be implemented on a broader scale.
Read more from the study here.