1
|
Gabr A, Zournas A, Stephens TG, Dismukes GC, Bhattacharya D. Evidence for a robust photosystem II in the photosynthetic amoeba Paulinella. THE NEW PHYTOLOGIST 2022; 234:934-945. [PMID: 35211975 DOI: 10.1111/nph.18052] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Accepted: 02/06/2022] [Indexed: 06/14/2023]
Abstract
Paulinella represents the only known case of an independent primary plastid endosymbiosis, outside Archaeplastida, that occurred c. 120 (million years ago) Ma. These photoautotrophs grow very slowly in replete culture medium with a doubling time of 6-7 d at optimal low light, and are highly sensitive to photodamage under moderate light levels. We used genomic and biophysical methods to investigate the extreme slow growth rate and light sensitivity of Paulinella, which are key to photosymbiont integration. All photosystem II (PSII) genes except psb28-2 and all cytochrome b6 f complex genes except petM and petL are present in Paulinella micropora KR01 (hereafter, KR01). Biophysical measurements of the water oxidation complex, variable chlorophyll fluorescence, and photosynthesis-irradiance curves show no obvious evidence of PSII impairment. Analysis of photoacclimation under high-light suggests that although KR01 can perform charge separation, it lacks photoprotection mechanisms present in cyanobacteria. We hypothesize that Paulinella species are restricted to low light environments because they are deficient in mitigating the formation of reactive oxygen species formed within the photosystems under peak solar intensities. The finding that many photoprotection genes have been lost or transferred to the host-genome during endosymbiont genome reduction, and may lack light-regulation, is consistent with this hypothesis.
Collapse
Affiliation(s)
- Arwa Gabr
- Graduate Program in Molecular Bioscience and Program in Microbiology and Molecular Genetics, Rutgers University, Nelson Lab-604 Allison Road, Piscataway, NJ, 08854, USA
| | - Apostolos Zournas
- Graduate Program in Chemical and Biochemical Engineering, Rutgers University, 98 Brett Road, Piscataway, NJ, 08854, USA
- The Waksman Institute, Rutgers University, 190 Frelinghuysen Road, Piscataway, NJ, 08854, USA
| | - Timothy G Stephens
- Department of Biochemistry and Microbiology, Rutgers University, Lipman Drive, New Brunswick, NJ, 08901, USA
| | - G Charles Dismukes
- The Waksman Institute, Rutgers University, 190 Frelinghuysen Road, Piscataway, NJ, 08854, USA
- Department of Chemistry and Chemical Biology, Rutgers University, 123 Bevier Road, Piscataway, NJ, 08854, USA
| | - Debashish Bhattacharya
- Department of Biochemistry and Microbiology, Rutgers University, Lipman Drive, New Brunswick, NJ, 08901, USA
| |
Collapse
|
2
|
Stephens TG, Gabr A, Calatrava V, Grossman AR, Bhattacharya D. Why is primary endosymbiosis so rare? THE NEW PHYTOLOGIST 2021; 231:1693-1699. [PMID: 34018613 PMCID: PMC8711089 DOI: 10.1111/nph.17478] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Accepted: 05/05/2021] [Indexed: 05/05/2023]
Abstract
Endosymbiosis is a relationship between two organisms wherein one cell resides inside the other. This affiliation, when stable and beneficial for the 'host' cell, can result in massive genetic innovation with the foremost examples being the evolution of eukaryotic organelles, the mitochondria and plastids. Despite its critical evolutionary role, there is limited knowledge about how endosymbiosis is initially established and how host-endosymbiont biology is integrated. Here, we explore this issue, using as our model the rhizarian amoeba Paulinella, which represents an independent case of primary plastid origin that occurred c. 120 million yr ago. We propose the 'chassis and engine' model that provides a theoretical framework for understanding primary plastid endosymbiosis, potentially explaining why it is so rare.
Collapse
Affiliation(s)
- Timothy G. Stephens
- Department of Biochemistry and Microbiology, Rutgers University, New Brunswick, NJ 08901, USA
| | - Arwa Gabr
- Graduate Program in Molecular Bioscience and Program in Microbiology and Molecular Genetics, Rutgers University, Piscataway, NJ 08854, USA
| | - Victoria Calatrava
- Department of Plant Biology, The Carnegie Institution, Stanford, CA 94305, USA
| | - Arthur R. Grossman
- Department of Plant Biology, The Carnegie Institution, Stanford, CA 94305, USA
| | - Debashish Bhattacharya
- Department of Biochemistry and Microbiology, Rutgers University, New Brunswick, NJ 08901, USA
| |
Collapse
|