The mechanisms whereby the green alga Chlorella ohadii, isolated from desert soil crust, exhibits unparalleled photodamage resistance

Haim Treves, Hagai Raanan, Isaac Kedem, Omer Murik, Nir Keren, Hagit Zer, Simon M. Berkowicz, Mario Giordano, Alessandra Norici, Yoram Shotland, Itzhak Ohad, Aaron Kaplan

Research output: Contribution to journalArticlepeer-review

Abstract

Excess illumination damages the photosynthetic apparatus with severe implications with regard to plant productivity. Unlike model organisms, the growth of Chlorella ohadii, isolated from desert soil crust, remains unchanged and photosynthetic O2 evolution increases, even when exposed to irradiation twice that of maximal sunlight. Spectroscopic, biochemical and molecular approaches were applied to uncover the mechanisms involved. D1 protein in photosystem II (PSII) is barely degraded, even when exposed to antibiotics that prevent its replenishment. Measurements of various PSII parameters indicate that this complex functions differently from that in model organisms and suggest that C. ohadii activates a nonradiative electron recombination route which minimizes singlet oxygen formation and the resulting photoinhibition. The light-harvesting antenna is very small and carotene composition is hardly affected by excess illumination. Instead of succumbing to photodamage, C. ohadii activates additional means to dissipate excess light energy. It undergoes major structural, compositional and physiological changes, leading to a large rise in photosynthetic rate, lipids and carbohydrate content and inorganic carbon cycling. The ability of C. ohadii to avoid photodamage relies on a modified function of PSII and the dissipation of excess reductants downstream of the photosynthetic reaction centers. The biotechnological potential as a gene source for crop plant improvement is self-evident.

Original languageEnglish
Pages (from-to)1229-1243
Number of pages15
JournalNew Phytologist
Volume210
Issue number4
DOIs
StatePublished - 1 Jun 2016
Externally publishedYes

Keywords

  • Algae
  • CO-concentrating mechanism
  • Photoinhibition
  • Photosynthesis
  • Stress

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