Format

Send to

Choose Destination
Photosynth Res. 2019 Feb 7. doi: 10.1007/s11120-019-00621-0. [Epub ahead of print]

The Antarctic psychrophiles Chlamydomonas spp. UWO241 and ICE-MDV exhibit differential restructuring of photosystem I in response to iron.

Author information

1
Department of Microbiology, Miami University, 700 E High St., 32 Pearson Hall, Oxford, OH, 45056, USA.
2
Land Resources and Environmental Sciences, Montana State University, Bozeman, MT, USA.
3
Department of Microbiology, Miami University, 700 E High St., 32 Pearson Hall, Oxford, OH, 45056, USA. morganr2@miamioh.edu.

Abstract

Chlamydomonas sp. UWO241 is a psychrophilic alga isolated from the deep photic zone of a perennially ice-covered Antarctic lake (east lobe Lake Bonney, ELB). Past studies have shown that C. sp. UWO241 exhibits constitutive downregulation of photosystem I (PSI) and high rates of PSI-associated cyclic electron flow (CEF). Iron levels in ELB are in the nanomolar range leading us to hypothesize that the unusual PSI phenotype of C. sp. UWO241 could be a response to chronic Fe-deficiency. We studied the impact of Fe availability in C. sp. UWO241, a mesophile, C. reinhardtii SAG11-32c, as well as a psychrophile isolated from the shallow photic zone of ELB, Chlamydomonas sp. ICE-MDV. Under Fe-deficiency, PsaA abundance and levels of photooxidizable P700 (ΔA820/A820) were reduced in both psychrophiles relative to the mesophile. Upon increasing Fe, C. sp. ICE-MDV and C. reinhardtii exhibited restoration of PSI function, while C. sp. UWO241 exhibited only moderate changes in PSI activity and lacked almost all LHCI proteins. Relative to Fe-excess conditions (200 µM Fe2+), C. sp. UWO241 grown in 18 µM Fe2+ exhibited downregulation of light harvesting and photosystem core proteins, as well as upregulation of a bestrophin-like anion channel protein and two CEF-associated proteins (NdsS, PGL1). Key enzymes of starch synthesis and shikimate biosynthesis were also upregulated. We conclude that in response to variable Fe availability, the psychrophile C. sp. UWO241 exhibits physiological plasticity which includes restructuring of the photochemical apparatus, increased PSI-associated CEF, and shifts in downstream carbon metabolism toward storage carbon and secondary stress metabolites.

KEYWORDS:

Antarctica; Cyclic electron flow; Iron; Photosystem I; Psychrophile

PMID:
30729447
DOI:
10.1007/s11120-019-00621-0

Supplemental Content

Full text links

Icon for Springer
Loading ...
Support Center