Synthetic glycolate metabolism pathways stimulate crop growth and productivity in the field

Abstract

Photorespiration is required in C3 plants to metabolize toxic glycolate formed when ribulose-1,5-bisphosphate carboxylase-oxygenase oxygenates rather than carboxylates ribulose-1,5-bisphosphate. Depending on growing temperatures, photorespiration can reduce yields by 20 to 50% in C3 crops. Inspired by earlier work, we installed into tobacco chloroplasts synthetic glycolate metabolic pathways that are thought to be more efficient than the native pathway. Flux through the synthetic pathways was maximized by inhibiting glycolate export from the chloroplast. The synthetic pathways tested improved photosynthetic quantum yield by 20%. Numerous homozygous transgenic lines increased biomass productivity between 19 and 37% in replicated field trials. These results show that engineering alternative glycolate metabolic pathways into crop chloroplasts while inhibiting glycolate export into the native pathway can drive increases in C3 crop yield under agricultural field conditions.

Net photosynthetic CO2 assimilation: more than just CO2 and O2 reduction cycles

“…This value probably changes to higher values when particular circumstances increase the nitrogen demand considerably despite low photorespiration, such as hypoxia (see above). Also, it would be interesting to disentangle the metabolism associated with nitrogen assimilation in genetically modified plants where photorespiration has been bypassed and plant biomass increases (Kebeish et al ., ; South et al ., ).…”

Photosynthesis in the fleeting shadows: an overlooked opportunity for increasing crop productivity?

“…Furthermore, wild ancestors of wheat showed higher A sat values than elite cultivars (Dunstone et al, 1973). Such influential early findings led to skepticism that photosynthesis can be improved in crops, and this view persists for some today, despite evidence that bioengineered increases in steady-state photosynthesis do correspond to significant increases in productivity (K€ ohler et al, 2016;Sinclair et al, 2019;South et al, 2019). Under field conditions, however, the light in a crop canopy is rarely constant.…”

Increasing plant group productivity through latent genetic variation for cooperation

“…Therefore, we refer to this naturally occurring genetic variation as latent variation for cooperation, since contributions to pathogen resistance rather than cooperation might have maintained the minor allele in the population. long term, biotechnological improvements of basic cellular functions including photosynthesis might pave the way to large productivity gains (36), but it is still unclear when and how such endeavors will materialize in improved yields of major crops (but see (37,38)). Others have proposed to re-evaluate whether breeding strategies of the Green Revolution, in particular the exploitation of G-I trade-offs, could be adopted for crops other than the graminoids wheat, rice, and barley, which so far have received most attention (21,23,39).…”