Structural re-arrangements of the thylakoid membranes are required for the activation of the Plastid Terminal Oxidase (PTOX) as a safety valve for photoprotection
Ontology highlight
ABSTRACT:
INSTRUMENT(S): Illumina HiSeq 4000
ORGANISM(S): Eutrema salsugineum
SUBMITTER: Leo Zeef
PROVIDER: E-MTAB-12913 | biostudies-arrayexpress |
REPOSITORIES: biostudies-arrayexpress
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Project description:Light is the driving force of photosynthesis. However, excessive light can be harmful. Photoinhibition, or lightinduced photodamage, is one of the key processes limiting photosynthesis. When the absorbed light exceeds the amount that can be dissipated by photosynthetic electron flow and other processes, damaging radicals are formed that mostly inactivate photosystem II (PSII). A welldefined mechanism that protects the photosynthetic apparatus from photoinhibition has been described in the model green alga Chlamydomonas reinhardtii and plants. Chlorella ohadii is a green microalga, isolated from biological desert soil crusts, that thrives under extreme high light (HL) in which other organisms do not survive. Here, we show that this alga evolved unique protection mechanisms distinct from those of C. reinhardtii and plants. When grown under extreme HL, significant structural changes were noted in the C. ohadii thylakoids, including a drastic reduction in the antennae and the formation of stripped core PSII, lacking its outer and inner antennae. 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, the stressrelated light harvesting complex (LHCSR), PSII protein phosphorylation and statetransitions are entirely absent or were barely detected in C. ohadii. A carotenoid biosynthesis related protein (CBR) is largely accumulated in the LHCII remains of HL cells and in the absence of psbS and LHCSR can function in sensing the HL and protecting from PI. Taken together, a unique photoinhibition protection mechanism evolved in C. ohadii, enabling the species to thrive under extremelight intensities where other photosynthetic organisms fail to survive.
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