03572nas a2200301   4500008004100000245010000041210006900141260001200210300001100222490000800233520264300241653002302884653001002907653002002917653002202937653002602959653001902985653001603004100002603020700002103046700002303067700001403090700002603104700002303130700001603153700002903169856007203198       2022                        eng d00aPhotosynthetic adaptation to polar life: Energy balance, photoprotection and genetic redundancy0 aPhotosynthetic adaptation to polar life Energy balance photoprot  c01/2022  a1535570 v2683 a<p>The persistent low temperature that characterize polar habitats combined with the requirement for light for all photoautotrophs creates a conundrum. The absorption of too much light at low temperature can cause an energy imbalance that decreases photosynthetic performance that has a negative impact on growth and can affect long-term survival. The goal of this review is to survey the mechanism(s) by which polar photoautotrophs maintain cellular energy balance, that is, photostasis to overcome the potential for cellular energy imbalance in their low temperature environments. Photopsychrophiles are photosynthetic organisms that are obligately adapted to low temperature (0-15 &deg;C) but usually die at higher temperatures (&ge;20 &deg;C). In contrast, photopsychrotolerant species can usually tolerate and survive a broad range of temperatures (5-40 &deg;C). First, we summarize the basic concepts of excess excitation energy, energy balance, photoprotection and photostasis and their importance to survival in polar habitats. Second, we compare the photoprotective mechanisms that underlie photostasis and survival in aquatic cyanobacteria and green algae as well as terrestrial Antarctic and Arctic plants. We show that polar photopsychrophilic and photopsychrotolerant organisms attain energy balance at low temperature either through a regulated reduction in the efficiency of light absorption or through enhanced capacity to consume photosynthetic electrons by the induction of O<sub>2</sub>&nbsp;as an alternative electron acceptor. Finally, we compare the published genomes of three photopsychrophilic and one photopsychrotolerant alga with five mesophilic green algae including the model green alga, <em>Chlamydomonas reinhardtii</em>. We relate our genomic analyses to photoprotective mechanisms that contribute to the potential attainment of photostasis. Finally, we discuss how the observed genomic redundancy in photopsychrophilic genomes may confer energy balance, photoprotection and resilience to their harsh polar environment. Primary production in aquatic, Antarctic and Arctic environments is dependent on diverse algal and cyanobacterial communities. Although mosses and lichens dominate the Antarctic terrestrial landscape, only two extant angiosperms exist in the Antarctic. The identification of a single &lsquo;molecular key&rsquo; to unravel adaptation of photopsychrophily and photopsychrotolerance remains elusive. Since these photoautotrophs represent excellent biomarkers to assess the impact of global warming on polar ecosystems, increased study of these polar photoautotrophs remains essential.</p>10agenomic redundancy10alight10aphotoprotection10aphotopsychrophily10aphotopsychrotolerance10aPhotosynthesis10atemperature1 aHüner, Norman, P. A.1 aSmith, David, R.1 aCvetkovska, Marina1 aZhang, Xi1 aIvanov, Alexander, G.1 aSzyszka-Mroz, Beth1 aKalra, Isha1 aMorgan-Kiss, Rachael, M.  uhttps://www.sciencedirect.com/science/article/pii/S017616172100196600640nas a2200157   4500008004100000245011400041210006900155300001200224490000700236100002400243700002600267700002100293700002300314700002400337856012100361       1998                        eng d00aStructure and composition of the photochemical apparatus of the Antarctic green alga Chlamydomonas subcaudata0 aStructure and composition of the photochemical apparatus of the   a303-3140 v561 aMorgan, Rachael, M.1 aIvanov, Alexander, G.1 aPriscu, John, C.1 aMaxwell, Denis, P.1 aHuner, Norman, P.A.  uhttps://mcm.lternet.edu/content/structure-and-composition-photochemical-apparatus-antarctic-green-alga-chlamydomonas