Abstract
BackgroundThe ice alga Chlamydomonas sp. ICE-L is the main contributor to primary productivity in Antarctic sea ice ecosystems and is well adapted to the extremely harsh environment. However, the adaptive mechanism of Chlamydomonas sp. ICE-L to sea-ice environment remains unclear. To study the adaptive strategies in Chlamydomonas sp. ICE-L, we investigated the molecular evolution of chloroplast photosynthetic genes that are essential for the accumulation of carbohydrate and energy living in Antarctic sea ice.ResultsThe 60 chloroplast protein-coding genes of Chlamydomonas sp. ICE-L were obtained, and the branch-site test detected significant signatures of positive selection on atpB, psaB, and rbcL genes in Chlamydomonas sp. ICE-L associated with the photosynthetic machinery. These positively selected genes were further identified as being under convergent evolution between Chlamydomonas sp. ICE-L and the halotolerant alga Dunaliella salina.ConclusionsOur study provides evidence that the phototrophic component of Chlamydomonas sp. ICE-L exhibits adaptive evolution under extreme environment. The positive Darwinian selection operates on the chloroplast protein-coding genes of Antarctic ice algae adapted to extreme environment following functional-specific and lineages-specific patterns. In addition, three positively selected genes with convergent substitutions in Chlamydomonas sp. ICE-L were identified, and the adaptive modifications in these genes were in functionally important regions of the proteins. Our study provides a foundation for future experiments on the biochemical and physiological impacts of photosynthetic genes in green algae.
Highlights
Our analyses revealed signatures of positive selection and convergent evolution among the chloroplast proteincoding genes of Antarctic ice algae, supporting the notion that the adaptation to extreme environments in algae are associated with the altered patterns of selection on chloroplast proteins
The goal of our study is to explore the role of positive selection in the adaptive patterns of Antarctic sea ice algae, four selected algae adapted to extreme environments are used to perform the selection analyses
ICE-L are related to extreme environmental adaptation, four algae living in extreme environments were selected for comparative evolutionary analyses
Summary
The Antarctic sea ice is an important constituent of the polar extreme environments, and it comprises a system of concentrated brine channels under low temperature, high salinity and low light conditions [2]. Survival in this harsh environment demands complex adaptations in physiology and metabolism. Comparative genomic analyses of three model organisms (Arabidopsis thaliana, Chlamydomonas reinhardtii and Thermosynechococcus elongatus) indicate that 48 chloroplast genes fall into two broad groups: 29 genes for the photosynthetic apparatus; 19 genes for components of the chloroplast genetic system These 29 chloroplast genes encode five photosynthetic complexes: photosystem I (PSI), photosystem II (PSII), Cytochrome b6f (Cytb6f ), ATP synthesis and Rubisco. The rbcL gene encoding Rubisco in many plants adapted to extreme environments shows various amino acid substitutions in Rubisco that influence abiotic stress responses [14]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
