Physiological characterization and light response of the CO₂-concentrating mechanism in the filamentous cyanobacterium Leptolyngbya sp. CPCC 696

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• 作者：Elvin D. de Araujo (1)
  Jason Patel (1)
  Charlotte de Araujo (2)
  Susan P. Rogers (3)
  Steven M. Short (14)
  Douglas A. Campbell (3)
  George S. Espie (12) george.espie@utoronto.ca
• 关键词：Ci pump/leak cycle – ; CO2 ; concentrating mechanism – ; CO2 uptake – ; Cyanobacteria – ; Leptolyngbya – ; Na+ ; dependent HCO3 − ; transport – ; Light response – ; Photoprotection – ; Photosynthesis
• 刊名：Photosynthesis Research
• 出版时间：September 2011
• 出版年：2011
• 期刊代码：20_01668595
• 类别：bus
• 卷：109
• 期：1-3
• 页码：85-101
• 数据来源：sp

摘要

We studied the interactions of the CO₂-concentrating mechanism and variable light in the filamentous cyanobacterium Leptolyngbya sp. CPCC 696 acclimated to low light (15 μmol m−2 s−1 PPFD) and low inorganic carbon (50 μM Ci). Mass spectrometric and polarographic analysis revealed that mediated CO₂ uptake along with both active Na+-independent and Na+-dependent HCO₃ − transport, likely through Na+/HCO₃ − symport, were employed to concentrate Ci internally. Combined transport of CO₂ and HCO₃ − required about 30 kJ mol−1 of energy from photosynthetic electron transport to support an intracellular Ci accumulation 550-fold greater than the external Ci. Initially, Leptolyngbya rapidly induced oxygen evolution and Ci transport to reach 40–50%of maximum values by 50 μmol m−2 s−1 PPFD. Thereafter, photosynthesis and Ci transport increased gradually to saturation around 1,800 μmol m−2 s−1 PPFD. Leptolyngbya showed a low intrinsic susceptibility to photoinhibition of oxygen evolution up to PPFD of 3,000 μmol m−2 s−1. Intracellular Ci accumulation showed a lag under low light but then peaked at about 500 μmol photons m−2 s−1 and remained high thereafter. Ci influx was accompanied by a simultaneous, light-dependent, outward flux of CO₂ and by internal CO₂/HCO₃ − cycling. The high-affinity and high-capacity CCM of Leptolyngbya responded dynamically to fluctuating PPFD and used excitation energy in excess of the needs of CO₂ fixation by increasing Ci transport, accumulation and Ci cycling. This capacity may allow Leptolyngbya to tolerate periodic exposure to excess high light by consuming electron equivalents and keeping PSII open.