Biology subjects

Clapero, V.

Publications and source records attributed to Clapero, V..

4 recordsLinked to original sources

bioRxiv2026

Intercellular Concentration Gradients of 3-Phosphoglycerate and Triose-Phosphate Demonstrate Operation of an Energy Shuttle in NAD-Malic Enzyme and Phosphoenolypyruvate Carboxykinase C4 Subtypes

In C4 photosynthesis, incoming CO2 is incorporated in mesophyll cells (MC) into 4-carbon acids that diffuse to bundle sheath cells (BSC) and decarboxylated to generate a high CO2 concentration that suppresses the oxygenation reaction of Rubisco. Decarboxylation can occur by NADP-malic enzyme, (NADP-ME), NAD-malic enzyme (NAD-ME) or phosphoenolpyruvate carboxykinase (PEPCK). NADP-ME generates NADPH in the BSC chloroplast and species that use it as the major route for decarboxylation typically have dimorphic BSC chloroplasts with little or no photosystem II. They operate an energy shuttle: much of the 3-phosphoglycerate formed in the Calvin-Benson cycle diffuses to the MC, enters the chloroplasts and is reduced to triose phosphates that return to the BSC. In species where carboxylation occurs mainly via NAD-ME or PEPCK, BSC chloroplasts possess photosystem II. Indirect evidence indicates they nevertheless have the capacity to operate an energy shuttle. We show here that NAD-ME and PEPCK species possess large pools of 3PGA and triose phosphates and, for two examples of each subtype, opposed concentration gradients of 3-phosphoglycerate and triose phosphates to drive rapid exchange between the BSC and MC. Reasons for and consequences of the widespread operation of the intercellular energy shuttle in C4 plants are discussed. Highlight StatementAn intercellular energy shuttle in which 3-phosphoglycerate moves from the bundle sheath to the mesophyll and triose phosphates return to the bundle sheath is a general feature of C4 photosynthesis.

plant biology↗

bioRxiv2026

Variance in Calvin-Benson cycle intermediate levels between closely-related species in the tomato clade

Published studies have reported species-variance between profiles of Calvin-Benson cycle (CBC) intermediates, not only between C4 species and C3 species, but also within C3 species (Arrivault et al., 2019, Borghi et al. 2019). It was proposed that this variance reflects lineage-dependent changes in the balance between different reactions, or poising, of the CBC. These earlier studies investigated phylogenetically-unrelated C3 species. In the current study, CBC intermediates were profiled in five closely-related species from Solanum sect. lycopersicon subsect. Lycopersicum. The levels of individual CBC intermediates showed many significant differences. In a principal component analysis, whilst three species (Solanum lycopersicum, Solanum cheesmaniae, Solanum neorickii) overlapped, Solanum pimpinellifolium and especially Solanum pennellii grouped separately, and were at opposing ends of the distribution. When combined with published data, whilst the separation between Solanum species was retained, they formed a group that was separated from five other C3 species, as well as two C4 species. It is discussed that the observed variation in CBC metabolites profiles within Solanum, together with their separation from other C3 species, supports the idea that CBC evolution is shaped both by phylogenetic relatedness and lineage-specific adaptation. HighlightVariance of intermediate levels points to poising of the Calvin-Benson cycle varying between closely-related species in the tomato clade Solanum sect. lycopersicon subsect. Lycopersicum

plant biology↗

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↗

bioRxiv2022

The genome sequence of Hirschfeldia incana, a species with high photosynthetic light-use efficiency

Photosynthesis is a biophysical and biochemical process that plays a key role in sustaining plant and human life, being the first step in the production of energy-rich molecules and oxygen in the biosphere. Improving the photosynthetic capacity of agricultural crops is highly desirable to increase their yields. While the core mechanisms of photosynthesis are highly conserved, certainly in higher plants, plants that can maintain a high photosynthetic light-use efficiency at high irradiance are exceptional and may be useful to understand and improve high irradiance photosynthesis of crops. One such exceptional species is Hirschfeldia incana, a member of the well-studied Brassicaceae family that is easy to grow under standard laboratory conditions, providing an excellent resource for studying the genetic and physiological basis of this trait. Here, we present a reference assembly of H. incana and affirm its high photosynthetic efficiency relative to the Brassicaceae species Brassica rapa, Brassica nigra, and Arabidopsis thaliana. We estimate that it diverged from B. rapa and B. nigra 10-11 million years ago and that its genome has diversified from that of the latter two species through large chromosomal rearrangements, species-specific transposon activity, and differential retention of duplicated genes. Genes present at copy numbers different from B. rapa and B. nigra include those involved in photosynthesis and/or abiotic stress, which may mediate the high photosynthetic efficiency of H. incana. We expect the reference assembly of H. incana to be a valuable genomic resource for identifying ways to enhance photosynthetic rates in crop species.

bioinformatics↗