Biology subjects

Rodrigues Gabriel Sales, C.

Publications and source records attributed to Rodrigues Gabriel Sales, C..

4 recordsLinked to original sources

bioRxiv2025

Sub-optimal temperature leads to tighter coupling between photosynthetic electron transport and CO2 assimilation under fluctuating light in maize.

The C4 carbon concentrating pathway promotes high CO2 assimilation rates. To keep C4 photosynthesis energetically efficient, electron transport reactions and downstream biochemistry need to be carefully balanced. Here we use a combination of non-invasive measurements and metabolic profiling to study the efficiency of C4 photosynthesis in maize under two conditions that can lead to decoupling between electron transport and carbon assimilation: fluctuating light and suboptimal temperature. Measurements were performed for three fluctuating light regimes and three temperatures, providing the most detailed study to date of the interaction between fluctuating light and suboptimal temperature on the photosynthetic performance of maize, an important global crop. At room temperature, CO2 assimilation rates were decoupled from photosynthetic electron transport under fluctuating light regimes, in contrast to tight coordination observed under constant light. This decoupling was underpinned by metabolic flexibility and buffering by large pools of C4 transfer metabolites. Surprisingly, at sub-optimal temperatures, CO2 assimilation rates became more tightly coupled to photosynthetic electron transport rates under fluctuating light regimes. This appeared to be caused by strong feedback downregulation of electron transport and a stronger degree of light-saturation of CO2 assimilation at low temperature. Low temperature impacted carbon assimilation rates more strongly than metabolite pools or intercellular metabolite distribution, which could reflect negative effects on diffusional metabolite transfer through plasmodesmata. Altogether, these results show that maize is able to maintain energetic efficiency by buffering light transitions under room temperature, as well as avoid oxidative damage by strongly downregulating electron transfer under short-term exposure to low temperature. One-sentence summaryAnalysis of maize CO2 assimilation under fluctuating light shows significant decoupling from photosynthetic electron transport at room temperature, supported by metabolic flexibility and buffering by large pools of C4 transfer metabolites, but tight coordination is restored under suboptimal temperature due to enhanced feedback regulation of electron transport and a stronger degree of light saturation of CO2 assimilation.

plant biology↗

bioRxiv2025

Faster relaxation of nonphotochemical quenching (NPQ) in C4 than in C3 species

Acceleration of photoprotective non-photochemical quenching (NPQ) responses to changes in light intensity has been suggested as a strategy to enhance crop yield. Despite many key crops utilising C4 photosynthesis, our current understanding of NPQ overwhelmingly comes from C3 species. Using a series of experiments on three phylogenetically controlled C3 and C4 comparisons, we show that NPQ relaxation is faster in C4 species. Temporal analysis of NPQ relaxation in leaves infiltrated with inhibitors to block proton motive force formation or xanthophyll de-epoxidation showed that the faster relaxation observed in C4 species is driven by a greater contribution of energy-dependent quenching (qE) to overall NPQ. We show that the C4-associated enhancement of qE is linked to altered regulation of lumen pH in C4 species, reflecting increases in cyclic electron flow and membrane proton conductivity to meet the increased ATP demands of the C4 pathway. Indeed, in two of the three tested C4 species, NPQ relaxation became significantly slower and statistically indistinguishable from paired C3 species when ATP and NADPH consumption was suppressed by performing measurements in CO2-free air. Altogether, our results suggest that NPQ responses in C4 species may already be optimised to maintain high photosynthetic efficiency in the fluctuating light conditions typically found within C4 canopies. Given the intrinsically faster NPQ in C4 photosynthesis, further acceleration of NPQ may have limited scope to enhance crop photosynthetic efficiency. Significance StatementAcceleration of non-photochemical quenching has been proposed as a means to enhance crop photosynthetic efficiency in C3 species but whether this strategy has potential in C4 species, which include several major crops, remains unclear. We use three phylogenetically paired C3 and C4 species to show that NPQ relaxation is significantly faster in species with the C4 pathway, possibly aiding the maintenance of photosynthetic efficiency in fluctuating light environments. As a result, accelerating the rate of NPQ relaxation in C4 crops may have a more limited scope to enhance photosynthesis.

plant biology↗

bioRxiv2025

Extensive photophysiological variation in wild barley is linked to environmental origin

O_LIIntraspecific variation between crop wild relatives (CWRs) represents a source of untapped genetic diversity for crop improvement. At the same time, improving photosynthesis in crops has the potential to enhance yield. Thus, exploring variation for photophysiology within CWRs is an important, yet underexplored, research area. C_LIO_LIWe describe a common garden experiment where 320 wild barley accessions were grown across two seasons. A photophysiology phenotyping pipeline was employed to quantify >30 traits within this diversity panel. Population genetics, genome-wide association analyses (GWAS) and deep phenotyping were performed to address local adaptation hypotheses. C_LIO_LIHeritable variation was detected across this photophysiological spectrum, with genotype-by-environment (GxE) interactions being prevalent. Evidence for local adaptation was observed in the form of subpopulation differences, signals of selection, and allele frequency variation associated to markers identified via GWAS. Phenotyping of representative accessions across distinct water availabilities highlighted a role for stomatal conductance (gs) in adaptation to dry environments. C_LIO_LIWe identified substantial variation in key photosynthesis-associated traits in a CWR closely related to barley, an economically important crop species. Our results demonstrate that this variation is partially due to local adaptation, where plasticity in gs appears important for maintaining photosynthesis and biomass accumulation in water restricted conditions. C_LI

plant biology↗

bioRxiv2023

Lessons from relatives: C4 photosynthesis enhances CO2 assimilation during the low-light phase of fluctuations.

Despite the global importance of species with C4 photosynthesis, there is a lack of consensus regarding C4 performance under fluctuating light. Contrasting hypotheses and experimental evidence suggest that C4 photosynthesis is either less, or more efficient in fixing carbon under fluctuating light than the ancestral C3 form. Two main issues were identified that may underly the lack of consensus: neglect of evolutionary distance between selected C3 and C4 species and use of contrasting fluctuating light treatments. To circumvent these issues, we compared photosynthetic responses to fluctuating light across three independent phylogenetically controlled comparisons between C3 and C4 species from Alloteropsis, Flaveria, and Cleome genera under 21% and 2% O2. Leaves were subjected to repetitive stepwise changes in light intensity (800 and 100 {micro}mol m-2 s-1 PFD) with three contrasting durations: 6, 30 and 300 seconds. These experiments reconcile the opposing results found across previous studies showing that 1) stimulation of CO2 assimilation in C4 species during the low light phase was both stronger and more sustained than in C3 species; 2) CO2 assimilation patterns during the high light phase were genus-specific rather than impacted by photosynthetic pathway; and 3) the duration of each light step in the fluctuation regime can strongly influence experimental outcomes. One sentence significance statementComparing photosynthesis in three pairs of closely related C3 and C4 species across three fluctuating light regimes showed that C4 photosynthesis has a systematic advantage under the low light phase not related to suppression of photorespiration, while the comparative efficiency under the high light phase was not determined by photosynthetic pathway.

plant biology↗