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<p>Due to low availability of CO<sub>2</sub> in aquatic environment, microalgae have evolved a CO<sub>2</sub> concentrating mechanism (CCM). It has long been thought that operation of CCM would suppress photorespiration by increasing the CO<sub>2</sub> concentration at the Rubisco active site, but experimental evidence is scarce. To better explore the function of photorespiration in algae, we first characterized a <i>Chlamydomonas reinhardtii</i> mutant defected in low-CO<sub>2</sub> inducible 20 (LCI20) and show that LCI20 is a chloroplast-envelope glutamate/malate transporter playing a role in photorespiration. By monitoring growth and glycolate excretion in mutants deficient in either CCM or photorespiration, we conclude that: (<i>i.</i>) CCM induction does not depend on photorespiration, (<i>ii.</i>)&#xa0;glycolate excretion together with glycolate dehydrogenase down-regulation prevents the toxic accumulation of non-metabolized photorespiratory metabolites,&#xa0;and&#xa0;(<i>iii</i>.) photorespiration is active at low CO<sub>2</sub> when the CCM is operational. This work provides a foundation for a better understanding of the carbon cycle in the ocean where significant glycolate concentrations have been found.</p>

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The green algae CO2 concentrating mechanism and photorespiration jointly operate during acclimation to low CO2

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年6月17日

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  • Ousmane Dao,
  • Marie Bertrand,
  • Saleh Alseekh,
  • Florian Veillet,
  • Pascaline Auroy,
  • Phuong-Chi Nguyen,
  • Bertrand Légeret,
  • Virginie Epting,
  • Amélie Morin,
  • Stephan Cuiné,
  • Caroline L. Monteil,
  • Luke C. M. Mackinder,
  • Adrien Burlacot,
  • Anja Krieger-Liszkay,
  • Andreas P. M. Weber,
  • Alisdair R. Fernie,
  • Gilles Peltier,
  • Yonghua Li-Beisson

摘要

Due to low availability of CO2 in aquatic environment, microalgae have evolved a CO2 concentrating mechanism (CCM). It has long been thought that operation of CCM would suppress photorespiration by increasing the CO2 concentration at the Rubisco active site, but experimental evidence is scarce. To better explore the function of photorespiration in algae, we first characterized a Chlamydomonas reinhardtii mutant defected in low-CO2 inducible 20 (LCI20) and show that LCI20 is a chloroplast-envelope glutamate/malate transporter playing a role in photorespiration. By monitoring growth and glycolate excretion in mutants deficient in either CCM or photorespiration, we conclude that: (i.) CCM induction does not depend on photorespiration, (ii.) glycolate excretion together with glycolate dehydrogenase down-regulation prevents the toxic accumulation of non-metabolized photorespiratory metabolites, and (iii.) photorespiration is active at low CO2 when the CCM is operational. This work provides a foundation for a better understanding of the carbon cycle in the ocean where significant glycolate concentrations have been found.