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

Kedem, Isaac; Milrad, Yuval; Yacoby, Iftach

doi:10.1007/s11120-020-00809-9

Cited by 14 publications

(10 citation statements)

References 74 publications

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“…Shade is scarce in this dry and arid landscape and to avoid PI, an alga inhabiting this ecosystem must be well‐adapted to the extremely intense light of the bright summer days (Hagemann et al., 2015; Hagemann et al., 2017). Previous studies revealed several such adaptation characteristics, including the shortest generation time of a photosynthetic eukaryote (Treves et al., 2016; Treves et al., 2017) a possible protective PSII‐cyclic electron flow and multiphasic growth governed by metabolic shifts (Ananyev et al., 2017; Kedem, Milrad, et al., 2021; Treves et al., 2017; Treves et al., 2020; Treves et al., 2022). We have previously shown how C. ohadii takes several known PI resistance mechanisms to the extreme.…”

Section: Introductionmentioning

confidence: 99%

A desert Chlorella sp. that thrives at extreme high‐light intensities using a unique photoinhibition protection mechanism

et al. 2023

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While light is the driving force of photosynthesis, excessive light can be harmful. Photoinhibition is one of the key processes that limit photosynthetic productivity. A well-defined mechanism that protects from photoinhibition has been described. Chlorella ohadii is a green micro-alga, isolated from biological desert soil crusts, which thrives under extreme high light (HL). Here, we show that this alga evolved unique protection mechanisms distinct from those of the green alga Chlamydomonas reinhardtii or plants. When grown under extreme HL, a drastic reduction in the size of light harvesting antennae occurs, resulting in the presence of core photosystem II, devoid of outer and inner antennas. This is accompanied by a massive accumulation of protective carotenoids and proteins that scavenge harmful radicals. At the same time, several elements central to photoinhibition protection in C. reinhardtii, such as psbS, light harvesting complex stress-related, photosystem II protein phosphorylation and state transitions are entirely absent or were barely detected. In addition, a carotenoid biosynthesis-related protein accumulates in the thylakoid membranes of HL cells and may function in sensing HL and protecting the cell from photoinhibition. Taken together, a unique photoinhibition protection mechanism evolved in C. ohadii, enabling the species to thrive under extreme-light intensities where other photosynthetic organisms fail to survive.

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Section: Introductionmentioning

confidence: 99%

A desert Chlorella sp. that thrives at extreme high‐light intensities using a unique photoinhibition protection mechanism

et al. 2023

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“…Another possibility of O 2 ‐independent photoproduction of ATP is cyclic electron flow around PSII, which might also decrease O 2 production by competing for absorbed photons. However, it is still not established whether such electron flow is coupled to pumping H + into the thylakoid lumen (Ananyev et al 2017; Kedem et al 2021). ATP synthesis coupled to PSI cyclic electron transport could, in the light, replace ATP production by fermentation under anoxia in the photic zone (Gfeller and Gibbs 1984).…”

Section: How Phytoplankton Deal With Low O2 Conditionsmentioning

confidence: 99%

Do phytoplankton require oxygen to survive? A hypothesis and model synthesis from oxygen minimum zones

Wong

Raven

Aldunate

et al. 2023

Limnology & Oceanography

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It is commonly known that phytoplankton have a pivotal role in marine biogeochemistry and ecosystems as carbon fixers and oxygen producers, but their response to deoxygenation has scarcely been studied. Nonetheless, in the major oceanic oxygen minimum zones (OMZs), all surface phytoplankton groups, regardless of size, disappear and are replaced by unique cyanobacteria lineages below the oxycline. To develop reasonable hypotheses to explain this pattern, we conduct a review of available information on OMZ phytoplankton, and we re-analyze previously published data (flow cytometric and hydrographic) on vertical structure of phytoplankton communities in relation to light and O 2 levels. We also review the physical constraints on O 2 acquisition as well as O 2 -dependent metabolisms in phototrophs. These considerations, along with estimates of the photosynthetic capacity of phytoplankton along OMZ depth profiles using published data, suggest that top-down grazing, respiratory demand, and irradiance are insufficient to fully explain the vertical structure observed in the upper, more sunlit portions of OMZs. Photorespiration and water-water cycles are O 2 -dependent pathways with low O 2 affinities. Although their metabolic roles are still poorly understood, a hypothetical dependence on such pathways by the phytoplankton adapted to the oxic ocean might explain vertical patterns in OMZs and results of laboratory experiments. This can be represented in a simple model in which the requirement for photorespiration in surface phytoplankton and O 2 -inhibition of OMZ lineages reproduces the observed vertical fluorescence profiles and the replacement of phytoplankton adapted to O 2 by lineages restricted to the most O 2 -deficient waters. A high O 2 requirement by modern phytoplankton would suggest a positive feedback that intensifies trends in OMZ extent and ocean oxygenation or deoxygenation, both in Earth's past and in response to current climate change.Deoxygenation in oceans is a growing phenomenon associated with anthropogenic climate change with several interacting causes that include changes in circulation and mixing, decreased solubility of oxygen (O 2 ) as temperature increases, and possibly biogeochemical changes (Ito et al., 2017;Schmidtko et al. 2017;Oschlies et al. 2018). The first evidence of a decline in dissolved O 2 was recorded in the 1980s (Horak et al. 2016;Ito et al. 2017). Oxygen minimum zones (OMZs) are naturally occurring zones where O 2 in sub-surface waters drops below a threshold that varies among authors but is

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“…Bonnanfant reported that Chlorella vulgaris managed short burst of high light (10 s or less) by quickening QA regeneration (22). Furthermore, Kedem recently exposed the role of PTOX (Plastid Terminal OXidase, an enzyme reverting PQH 2 to PQ in the waterwater cycle) in the mechanisms deployed by a Chlorella species to cope with high light (31). Hence, intense conversion of PQH 2 to PQ regenerates the QA pool, mechanically increasing the needed turnovers to reach saturation, delay- This unusual behavior raised the question of a potential malfunctioning of the reaction centers.…”

Section: Pigment Contentsmentioning

confidence: 99%

“…Three studies seem to point out that this type of cultivation is possible. They were conducted on wellstirred optically dense cultures under 3000, 7000, and 8000 µmolPhotonPAR/m 2 /s respectively (31)(32)(33). In these cases, the combination of the light gradient inside of the culture and the constant mixing supposedly induced an adequate perceived light pattern allowing the cells to grow.…”

Section: Introductionmentioning

confidence: 99%

Chlorella vulgaris cultivation under super high light intensity: An application of the flashing light effect

Pozzobon¹

2022

Algal Research

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

Cited by 14 publications

References 74 publications

A desert Chlorella sp. that thrives at extreme high‐light intensities using a unique photoinhibition protection mechanism

A desert Chlorella sp. that thrives at extreme high‐light intensities using a unique photoinhibition protection mechanism

Do phytoplankton require oxygen to survive? A hypothesis and model synthesis from oxygen minimum zones

Chlorella vulgaris cultivation under super high light intensity: An application of the flashing light effect

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