Abstract
Diacylglycerol acyl-transferase (DGAT) and cysteine oleosin (CO) expression confers a novel carbon sink (of encapsulated lipid droplets) in leaves of Lolium perenne and has been shown to increase photosynthesis and biomass. However, the physiological mechanism by which DGAT + CO increases photosynthesis remains unresolved. To evaluate the relationship between sink strength and photosynthesis, we examined fatty acids (FA), water-soluble carbohydrates (WSC), gas exchange parameters and leaf nitrogen for multiple DGAT + CO lines varying in transgene accumulation. To identify the physiological traits which deliver increased photosynthesis, we assessed two important determinants of photosynthetic efficiency, CO2 conductance from atmosphere to chloroplast, and nitrogen partitioning between different photosynthetic and non-photosynthetic pools. We found that DGAT + CO accumulation increased FA at the expense of WSC in leaves of L. perenne and for those lines with a significant reduction in WSC, we also observed an increase in photosynthesis and photosynthetic nitrogen use efficiency. DGAT + CO L. perenne displayed no change in rubisco content or Vcmax but did exhibit a significant increase in specific leaf area (SLA), stomatal and mesophyll conductance, and leaf nitrogen allocated to photosynthetic electron transport. Collectively, we showed that increased carbon demand via DGAT+CO lipid sink accumulation can induce leaf-level changes in L. perenne which deliver increased rates of photosynthesis and growth. Carbon sinks engineered within photosynthetic cells provide a promising new strategy for increasing photosynthesis and crop productivity.
Highlights
Global food security remains one of the most pressing issues of our time
In this study we described three experiments examining the relationships between photosynthesis, leaf N, and an engineered carbon sink in leaves of L. perenne
In experiment 1, we tested whether increasing sink capacity via Diacylglycerol acyl-transferase (DGAT) + cysteine oleosin (CO) accumulation corresponded to increased photosynthesis
Summary
With increasing population and food production needs, enhancing photosynthesis represents a major target for improving crop productivity (Evans and Lawson, 2020). Several bioengineering strategies have targeted improvements in the efficiency of photosynthetic energy conversion and photo-assimilate production, e.g., carbon concentrating mechanisms (Atkinson et al, 2016), C4 rice (Ermakova et al, 2020) and photorespiratory bypasses (Xin et al, 2015). The importance of photo-assimilate utilization to maintain photosynthetic capacity is becoming increasingly apparent (Ainsworth and Bush, 2011; Jansson et al, 2018; Dingkuhn et al, 2020). Increasing the sink capacity of leaves represents a promising strategy to maximize the photosynthetic potential of crops
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
