02098nas a2200265 4500008004100000022001400041245010400055210006900159260001200228300001200240490000800252520131200260653001601572653001501588653001801603653002501621653002101646653001301667653002201680100001601702700001401718700001401732700002901746856005701775 2023 eng d a0166-859500aHigh salt-induced PSI-supercomplex is associated with high CEF and attenuation of state transitions0 aHigh saltinduced PSIsupercomplex is associated with high CEF and c09/2023 a65 - 840 v1573 a

While PSI-driven cyclic electron flow (CEF) and assembly of thylakoid supercomplexes have been described in model organisms like Chlamydomonas reinhardtii, open questions remain regarding their contributions to survival under long-term stress. The Antarctic halophyte, C. priscuii UWO241 (UWO241), possesses constitutive high CEF rates and a stable PSI-supercomplex as a consequence of adaptation to permanent low temperatures and high salinity. To understand whether CEF represents a broader acclimation strategy to short- and long-term stress, we compared high salt acclimation between the halotolerant UWO241, the salt-sensitive model, C. reinhardtii, and a moderately halotolerant Antarctic green alga, C. sp. ICE-MDV (ICE-MDV). CEF was activated under high salt and associated with increased non-photochemical quenching in all three Chlamydomonas species. Furthermore, high salt-acclimated cells of either strain formed a PSI-supercomplex, while state transition capacity was attenuated. How the CEF-associated PSI-supercomplex interferes with state transition response is not yet known. We present a model for interaction between PSI-supercomplex formation, state transitions, and the important role of CEF for survival during long-term exposure to high salt.

10aacclimation10aAntarctica10aChlamydomonas10aCyclic electron flow10aPSI-supercomplex10asalinity10astate transitions1 aKalra, Isha1 aWang, Xin1 aZhang, Ru1 aMorgan-Kiss, Rachael, M. uhttps://link.springer.com/10.1007/s11120-023-01032-y02015nas a2200217 4500008004100000245016100041210006900202260001200271490000700283520122000290653001501510653001801525653002301543653003901566653001601605653003001621100002301651700002901674700002401703856007001727 2020 eng d00aGlycerol is an osmoprotectant in two Antarctic Chlamydomonas species from an ice-covered saline lake and is synthesized by an unusual bidomain enzyme0 aGlycerol is an osmoprotectant in two Antarctic IChlamydomonasI s c08/20200 v113 a

Glycerol, a compatible solute, has previously been found to act as an osmoprotectant in some marine Chlamydomonas species and several species of Dunaliella from hypersaline ponds. Recently, Chlamydomonas reinhardtii and Dunaliella salina were shown to make glycerol with an unusual bidomain enzyme, which appears to be unique to algae, that contains a phosphoserine phosphatase and glycerol-3-phosphate dehydrogenase. Here we report that two psychrophilic species of Chlamydomonas (C. spp. UWO241 and ICE-MDV) from Lake Bonney, Antarctica also produce high levels of glycerol to survive in the lake’s saline waters. Glycerol concentration increased linearly with salinity and at 1.3 M NaCl, exceeded 400 mM in C. sp. UWO241, the more salt-tolerant strain. We also show that both species expressed several isoforms of the bidomain enzyme. An analysis of one of the isoforms of C. sp. UWO241 showed that it was strongly upregulated by NaCl and is thus the likely source of glycerol. These results reveal another adaptation of the Lake Bonney Chlamydomonas species that allow them to survive in an extreme polar environment.

10aAntarctica10aChlamydomonas10aglycerol synthesis10aglycerol-3-phosphate dehydrogenase10aLake Bonney10aphosphoserine phosphatase1 aRaymond, James, A.1 aMorgan-Kiss, Rachael, M.1 aStahl-Rommel, Sarah uhttps://www.frontiersin.org/articles/10.3389/fpls.2020.01259/full