Engineering Strategies to Boost Crop Productivity by Cutting Respiratory Carbon Loss

Abstract

Roughly half the carbon that crop plants fix by photosynthesis is subsequently lost by respiration. Nonessential respiratory activity leading to unnecessary CO 2 release is unlikely to have been minimized by natural selection or crop breeding, and cutting this large loss could complement and reinforce the currently dominant yield-enhancement strategy of increasing carbon fixation. Until now, however, respiratory carbon losses have generally been overlooked by metabolic engineers and synthetic biologists because specific target genes have been elusive. We argue that recent advances are at last pinpointing individual enzyme and transporter genes that can be engineered to (1) slow unnecessary protein turnover, (2) replace, relocate, or reschedule metabolic activities, (3) suppress futile cycles, and (4) make ion transport more efficient, all of which can reduce respiratory costs. We identify a set of engineering strategies to reduce respiratory carbon loss that are now feasible and model how implementing these strategies singly or in tandem could lead to substantial gains in crop productivity.

Energy costs of salt tolerance in crop plants

“…when the pump is not activated (Pedersen et al, 2018)) would reduce the energy efficiency substantially; it is interesting that cytosolic K + and potentially Na + can have an effect on this (Buch-Pedersen et al, 2006). The identification of molecular components of energetically costly processes can be used to engineer plants for improved yield (Amthor et al, 2019).…”

The importance of thiamine (vitamin B1) in plant health: From crop yield to biofortification

“…Efforts in enhancing crop productivity and yields have largely concentrated on increasing photosynthetic carbon assimilation in the Calvin cycle and transfer of this carbon into storage sinks, such as starchy cereal grains or tubers (64,65). Efforts have also been made to reduce the respiratory losses of plants and their maintenance costs, allowing more resources to be directed into biosynthesis and growth (66). In the context of thiamine, it has recently been proposed that reengineering more stable and nonsuicide versions of thiamine biosynthesis enzymes offers the potential to reduce the energetic costs of thiamine biosynthesis and puts forward ideas of how it could impact crop yield potential (67).…”

Potential For Applying Continuous Directed Evolution To Plant Enzymes

“…Plant and yeast THI4s are suicide enzymes that self-inactivate after a single catalytic cycle because they obtain the sulfur atom needed to form the thiazole product by destroying an active-site cysteine residue. Such THI4s are consequently energetically expensive to operate [3,[33][34][35]. In contrast, certain prokaryotic THI4s are truly catalytic, i.e.…”

“…Extending enzyme life. The unnecessarily short working lives of certain plant enzymes wastes resources[3]. Short life is likely due in part to damage to active site residues by chemically reactive substrates or products or by catalytic misfires[61].A recently introduced metric for enzyme working life -Catalytic-Cycles-till-Replacement (CCR) = [Metabolic flux rate] / [Enzyme replacement rate]helps identify enzymes that are candidates for life-lengthening [61].…”