Marine diatoms are key primary producers across diverse habitats in the global ocean. Diatoms rely on a biophysical carbon concentrating mechanism (CCM) to supply high concentrations of CO2around their carboxylating enzyme, RuBisCO. The necessity and energetic cost of the CCM are likely to be highly sensitive to temperature, as temperature impacts CO2concentration, diffusivity, and the kinetics of CCM components. Here, we used membrane inlet mass spectrometry (MIMS) and modeling to capture temperature regulation of the CCM in the diatom
Photosynthetic inefficiencies limit the productivity and sustainability of crop production and the resilience of agriculture to future societal and environmental challenges. Rubisco is a key target for improvement as it plays a central role in carbon fixation during photosynthesis and is remarkably inefficient. Introduction of mutations to the chloroplast‐encoded Rubisco large subunit
- Award ID(s):
- 1642386
- NSF-PAR ID:
- 10453705
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- The Plant Journal
- Volume:
- 106
- Issue:
- 3
- ISSN:
- 0960-7412
- Page Range / eLocation ID:
- p. 876-887
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Phaeodactylum tricornutum (Pt) . We found that enhanced carbon fixation rates byPt at elevated temperatures were accompanied by increased CCM activity capable of maintaining RuBisCO close to CO2saturation but that the mechanism varied. At 10 and 18 °C, diffusion of CO2into the cell, driven byPt ’s ‘chloroplast pump’ was the major inorganic carbon source. However, at 18 °C, upregulation of the chloroplast pump enhanced (while retaining the proportion of) both diffusive CO2and active HCO3−uptake into the cytosol, and significantly increased chloroplast HCO3−concentrations. In contrast, at 25 °C, compared to 18 °C, the chloroplast pump had only a slight increase in activity. While diffusive uptake of CO2into the cell remained constant, active HCO3−uptake across the cell membrane increased resulting inPt depending equally on both CO2and HCO3−as inorganic carbon sources. Despite changes in the CCM, the overall rate of active carbon transport remained double that of carbon fixation across all temperatures tested. The implication of the energetic cost of thePt CCM in response to increasing temperatures was discussed. -
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Summary Photosynthesis in C3 plants is limited by features of the carbon‐fixing enzyme Rubisco, which exhibits a low turnover rate and can react with O2instead of
CO 2, leading to photorespiration. In cyanobacteria, bacterial microcompartments, known as carboxysomes, improve the efficiency of photosynthesis by concentratingCO 2near the enzyme Rubisco. Cyanobacterial Rubisco enzymes are faster than those of C3 plants, though they have lower specificity towardCO 2than the land plant enzyme. Replacement of land plant Rubisco by faster bacterial variants with lowerCO 2specificity will improve photosynthesis only if a microcompartment capable of concentratingCO 2can also be installed into the chloroplast. We review current information about cyanobacterial microcompartments and carbon‐concentrating mechanisms, plant transformation strategies, replacement of Rubisco in a model C3 plant with cyanobacterial Rubisco and progress toward synthesizing a carboxysome in chloroplasts. -
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Summary The transition from pollinator‐mediated outbreeding to selfing has occurred many times in angiosperms. This is generally accompanied by a reduction in traits attracting pollinators, including reduced emission of floral scent. In
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Introgression can produce novel genetic variation in organisms that hybridize. Sympatric species pairs in the carnivorous plant genus
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Higher order mutants defective in CLP or PREP proteins were generated and analyzed by quantitative proteomics and N‐terminal proteomics (terminal amine isotopic labeling of substrates (TAILS)).
Strong synergistic interactions were observed between the CLP protease system (
clpr1‐2 ,clpr2‐1 ,clpc1‐1 ,clpt1 ,clpt2) and both PREP homologs (prep1 ,prep2 ) resulting in embryo lethality or growth and developmental phenotypes. Synergistic interactions were observed even when only one of the PREP proteins was lacking, suggesting that PREP1 and PREP2 have divergent substrates. Proteome phenotypes were driven by the loss of CLP protease capacity, with little impact from the PREP peptidases. Chloroplast N‐terminal proteomess howed that many nuclear encoded chloroplast proteins have alternatively processed N‐termini inprep1prep2 ,clpt1clpt2 andprep1prep2clpt1clpt2 .Loss of chloroplast protease capacity interferes with stromal processing peptidase (SPP) activity due to folding stress and low levels of accumulated cleaved cTP fragments. PREP1,2 proteolysis of cleaved cTPs is complemented by unknown proteases. A model for CLP and PREP activity within a hierarchical chloroplast proteolysis network is proposed.
