title: Arctic Micromonas uses protein pools and non-photochemical quenching to cope with temperature restrictions on Photosystem II protein turnover.
abstract: Micromonas strains of small prasinophyte green algae are found throughout the world's oceans, exploiting widely different niches. We grew arctic and temperate strains of Micromonas and compared their susceptibilities to photoinactivation of Photosystem II, their counteracting Photosystem II repair capacities, their Photosystem II content, and their induction and relaxation of non-photochemical quenching. In the arctic strain Micromonas NCMA 2099, the cellular content of active Photosystem II represents only about 50 % of total Photosystem II protein, as a slow rate constant for clearance of PsbA protein limits instantaneous repair. In contrast, the temperate strain NCMA 1646 shows a faster clearance of PsbA protein which allows it to maintain active Photosystem II content equivalent to total Photosystem II protein. Under growth at 2 °C, the arctic Micromonas maintains a constitutive induction of xanthophyll deepoxidation, shown by second-derivative whole-cell spectra, which supports strong induction of non-photochemical quenching under low to moderate light, even if xanthophyll cycling is blocked. This non-photochemical quenching, however, relaxes during subsequent darkness with kinetics nearly comparable to the temperate Micromonas NCMA 1646, thereby limiting the opportunity cost of sustained downregulation of PSII function after a decrease in light.
authors.affiliation: Department of Chemistry & Biochemistry, Mount Allison University, 63B York St., Sackville, NB, E4L3M7, Canada.|Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, CAS, Guangzhou, 510160, China.
authors.forename: Guangyan
authors.initials: G
authors.lastname: Ni
authors.affiliation: Department of Chemistry & Biochemistry, Mount Allison University, 63B York St., Sackville, NB, E4L3M7, Canada.
authors.forename: Gabrielle
authors.initials: G
authors.lastname: Zimbalatti
authors.affiliation: Department of Chemistry & Biochemistry, Mount Allison University, 63B York St., Sackville, NB, E4L3M7, Canada.
authors.forename: Cole D
authors.initials: CD
authors.lastname: Murphy
authors.affiliation: Michigan Technological University, Houghton, MI, 49931, USA.
authors.forename: Audrey B
authors.initials: AB
authors.lastname: Barnett
authors.affiliation: Department of Chemistry & Biochemistry, Mount Allison University, 63B York St., Sackville, NB, E4L3M7, Canada.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Arsenault
authors.affiliation: Department of Chemistry & Biochemistry, Mount Allison University, 63B York St., Sackville, NB, E4L3M7, Canada.|Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, CAS, Guangzhou, 510301, China.
authors.forename: Gang
authors.initials: G
authors.lastname: Li
authors.affiliation: Department of Chemistry & Biochemistry, Mount Allison University, 63B York St., Sackville, NB, E4L3M7, Canada.
authors.forename: Amanda M
authors.initials: AM
authors.lastname: Cockshutt
authors.affiliation: Department of Chemistry & Biochemistry, Mount Allison University, 63B York St., Sackville, NB, E4L3M7, Canada. dcampbell@mta.ca.
authors.forename: Douglas A
authors.identifier: http://orcid.org/0000-0001-8996-5463
authors.initials: DA
authors.lastname: Campbell
mesh_terms: D001110:Arctic Regions; D000460:Chlorophyta / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism*; D013696:Temperature
chemical_list: D045332:Photosystem II Protein Complex; D010940:Plant Proteins
keywords: Photoinactivation; Photosystem II; Prasinophyte; Xanthophyll cycle