Juggling Lightning: How Chlorella ohadii handles extreme energy inputs without damage

Isaac Kedem, Yuval Milrad, Aaron Kaplan*, Iftach Yacoby

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

The green alga Chlorella ohadii was isolated from a desert biological soil crust, one of the harshest environments on Earth. When grown under optimal laboratory settings it shows the fastest growth rate ever reported for a photosynthetic eukaryote and a complete resistance to photodamage even under unnaturally high light intensities. Here we examined the energy distribution along the photosynthetic pathway under four light and carbon regimes. This was performed using various methodologies such as membrane inlet mass spectrometer with stable O2 isotopes, variable fluorescence, electrochromic shift and fluorescence assessment of NADPH level, as well as the use of specific inhibitors. We show that the preceding illumination and CO2 level during growth strongly affect the energy dissipation strategies employed by the cell. For example, plastid terminal oxidase (PTOX) plays an important role in energy dissipation, particularly in high light- and low-CO2-grown cells. Of particular note is the reliance on PSII cyclic electron flow as an effective and flexible dissipation mechanism in all conditions tested. The energy management observed here may be unique to C. ohadii, as it is the only known organism to cope with such conditions. However, the strategies demonstrated may provide an insight into the processes necessary for photosynthesis under high-light conditions.

Original languageEnglish
Pages (from-to)329-344
Number of pages16
JournalPhotosynthesis Research
Volume147
Issue number3
DOIs
StatePublished - Mar 2021

Funding

FundersFunder number
Israeli Ministry for Science and Technology
Israel Science Foundation

    Keywords

    • BSC
    • Energy dissipation
    • Fluorescence
    • High illumination
    • Oxygen evolution
    • PTOX

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