By Stephanie Baum and Andrew Zinin
In efforts to better understand how plant photosynthesis is regulated, scientists are studying how Rubisco activity responds to light. In a new meta-analysis study, a team from the Realizing Increased Photosynthetic Efficiency (RIPE) project at Lancaster University have identified a potential link between photosynthetic pathway type and rates of dark inhibition. The findings are published in the Journal of Experimental Botany.
Rubisco, the most abundant enzyme on Earth, is essential for photosynthesis. It takes carbon dioxide from the atmosphere and creates usable sugar molecules. In many plant species, a nocturnal inhibitor molecule called CA1P builds up in darkness and low light, blocking the activity of Rubisco. In the light, CA1P is broken down and Rubisco activity is restored. This phenomenon is called dark inhibition.
CA1P levels—and consequently, dark inhibition rates—vary widely between plant species, even among closely related ones. Why plants have this on/off switch, and why its prevalence varies so widely across species, has remained poorly understood.
Lancaster University researchers Connor Nehls-Ramos and Assistant Professor Doug Orr set out to explore an evolutionary connection for the wide variation of dark inhibition rates across all flowering plants. A deeper understanding of how and why CA1P regulates Rubisco activity could help inform future efforts to engineer photosynthesis for crops with improved yield and efficiency.
"If we look at this from an evolutionary point of view, we may be able to find certain trends in adaptation across different groups of plants," said Nehls-Ramos. "We have lots of questions about this nocturnal inhibitor. Why would certain plants carry this trait while others have seemingly no dark inhibition? Is dark inhibition a new thing, or is it a carry-over from a more ancient metabolic process? Are these different inhibition levels indicating something more nuanced in chloroplast regulation?"
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