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Clade-Specific Quantitative Analysis of Photosynthetic Gene Expression in Prochlorococcus.

Fernández-Pinos MC, Casado M, Caballero G, Zinser ER, Dachs J, Piña B - PLoS ONE (2015)

Bottom Line: After optimizing sample collection methodology, we analyzed a total of 62 stations from the Malaspina 2010 circumnavigation (including Atlantic, Pacific and Indian Oceans) at three different depths.Sequence and quantitative analyses of the corresponding amplicons showed the presence of high-light (HL) and low-light (LL) Prochlorococcus clades in essentially all 182 samples, with a largely uniform stratification of LL and HL sequences.Synechococcus cross-amplifications were detected by the taxon-specific melting temperatures of the amplicons.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Chemistry, IDAEA-CSIC, Barcelona, Catalonia, Spain.

ABSTRACT
Newly designed primers targeting rbcL (CO2 fixation), psbA (photosystem II) and rnpB (reference) genes were used in qRT-PCR assays to assess the photosynthetic capability of natural communities of Prochlorococcus, the most abundant photosynthetic organism on Earth and a major contributor to primary production in oligotrophic oceans. After optimizing sample collection methodology, we analyzed a total of 62 stations from the Malaspina 2010 circumnavigation (including Atlantic, Pacific and Indian Oceans) at three different depths. Sequence and quantitative analyses of the corresponding amplicons showed the presence of high-light (HL) and low-light (LL) Prochlorococcus clades in essentially all 182 samples, with a largely uniform stratification of LL and HL sequences. Synechococcus cross-amplifications were detected by the taxon-specific melting temperatures of the amplicons. Laboratory exposure of Prochlorococcus MED4 (HL) and MIT9313 (LL) strains to organic pollutants (PAHs and organochlorine compounds) showed a decrease of rbcL transcript abundances, and of the rbcL to psbA ratios for both strains. We propose this technique as a convenient assay to evaluate effects of environmental stressors, including pollution, on the oceanic Prochlorococcus photosynthetic function.

No MeSH data available.


Related in: MedlinePlus

Graphic representation of the different temporal responses of MED4 (green circles) and MIT9313 (blue triangles) to pollutants.Results from PAH and OClP treatments are pooled together. Significant differences in mRNA abundance between treated and untreated cultures are marked with asterisks (*, p<0.05; **, p<0.01). Whiskers indicate 95% confidence limits.
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pone.0133207.g005: Graphic representation of the different temporal responses of MED4 (green circles) and MIT9313 (blue triangles) to pollutants.Results from PAH and OClP treatments are pooled together. Significant differences in mRNA abundance between treated and untreated cultures are marked with asterisks (*, p<0.05; **, p<0.01). Whiskers indicate 95% confidence limits.

Mentions: Exposure of experimental Prochlorococcus MED4 and MIT9313 cultures to either PAHs or OClP mixtures did not affect significantly growth rates or chlorophyll contents (S5 and S6 Tables). However, treated cultures showed a decrease of the rbcL mRNA levels relative to control cultures, an effect not observed for psbA (Table 6). Combining data for all treatments, rbcL mRNA levels were reduced by 20% relative to the reference gene, a moderate, but significant decrease (Table 6). These data suggest that pollutants may alter the relative expression of photosynthetic genes, an effect likely to be added to the influence of other natural effectors we observed in the natural oceanic populations sampled at different depths (Fig 2). The analysis of the influence of different parameters on the effects of pollutants in rbcL expression (3-way ANOVA) indicated “time of exposure” as the only single factor with significant between-subject effects, as well as an interaction between “time of exposure” and “strain” (Table 6). These interactions can be visualized in Fig 5, which shows a decrease of the rbcL expression and of the rbcL/psbA ratio only after 24 hours of treatment for MIT9313, whereas for MED4 both values decreased during the first 0.5 h of exposure, recovering afterwards. While these results should be regarded only as indicative, they suggest that different Prochlorococcus strains may have different susceptibilities to organic pollutants, and that their temporal response to them may also differ.


Clade-Specific Quantitative Analysis of Photosynthetic Gene Expression in Prochlorococcus.

Fernández-Pinos MC, Casado M, Caballero G, Zinser ER, Dachs J, Piña B - PLoS ONE (2015)

Graphic representation of the different temporal responses of MED4 (green circles) and MIT9313 (blue triangles) to pollutants.Results from PAH and OClP treatments are pooled together. Significant differences in mRNA abundance between treated and untreated cultures are marked with asterisks (*, p<0.05; **, p<0.01). Whiskers indicate 95% confidence limits.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4526520&req=5

pone.0133207.g005: Graphic representation of the different temporal responses of MED4 (green circles) and MIT9313 (blue triangles) to pollutants.Results from PAH and OClP treatments are pooled together. Significant differences in mRNA abundance between treated and untreated cultures are marked with asterisks (*, p<0.05; **, p<0.01). Whiskers indicate 95% confidence limits.
Mentions: Exposure of experimental Prochlorococcus MED4 and MIT9313 cultures to either PAHs or OClP mixtures did not affect significantly growth rates or chlorophyll contents (S5 and S6 Tables). However, treated cultures showed a decrease of the rbcL mRNA levels relative to control cultures, an effect not observed for psbA (Table 6). Combining data for all treatments, rbcL mRNA levels were reduced by 20% relative to the reference gene, a moderate, but significant decrease (Table 6). These data suggest that pollutants may alter the relative expression of photosynthetic genes, an effect likely to be added to the influence of other natural effectors we observed in the natural oceanic populations sampled at different depths (Fig 2). The analysis of the influence of different parameters on the effects of pollutants in rbcL expression (3-way ANOVA) indicated “time of exposure” as the only single factor with significant between-subject effects, as well as an interaction between “time of exposure” and “strain” (Table 6). These interactions can be visualized in Fig 5, which shows a decrease of the rbcL expression and of the rbcL/psbA ratio only after 24 hours of treatment for MIT9313, whereas for MED4 both values decreased during the first 0.5 h of exposure, recovering afterwards. While these results should be regarded only as indicative, they suggest that different Prochlorococcus strains may have different susceptibilities to organic pollutants, and that their temporal response to them may also differ.

Bottom Line: After optimizing sample collection methodology, we analyzed a total of 62 stations from the Malaspina 2010 circumnavigation (including Atlantic, Pacific and Indian Oceans) at three different depths.Sequence and quantitative analyses of the corresponding amplicons showed the presence of high-light (HL) and low-light (LL) Prochlorococcus clades in essentially all 182 samples, with a largely uniform stratification of LL and HL sequences.Synechococcus cross-amplifications were detected by the taxon-specific melting temperatures of the amplicons.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Chemistry, IDAEA-CSIC, Barcelona, Catalonia, Spain.

ABSTRACT
Newly designed primers targeting rbcL (CO2 fixation), psbA (photosystem II) and rnpB (reference) genes were used in qRT-PCR assays to assess the photosynthetic capability of natural communities of Prochlorococcus, the most abundant photosynthetic organism on Earth and a major contributor to primary production in oligotrophic oceans. After optimizing sample collection methodology, we analyzed a total of 62 stations from the Malaspina 2010 circumnavigation (including Atlantic, Pacific and Indian Oceans) at three different depths. Sequence and quantitative analyses of the corresponding amplicons showed the presence of high-light (HL) and low-light (LL) Prochlorococcus clades in essentially all 182 samples, with a largely uniform stratification of LL and HL sequences. Synechococcus cross-amplifications were detected by the taxon-specific melting temperatures of the amplicons. Laboratory exposure of Prochlorococcus MED4 (HL) and MIT9313 (LL) strains to organic pollutants (PAHs and organochlorine compounds) showed a decrease of rbcL transcript abundances, and of the rbcL to psbA ratios for both strains. We propose this technique as a convenient assay to evaluate effects of environmental stressors, including pollution, on the oceanic Prochlorococcus photosynthetic function.

No MeSH data available.


Related in: MedlinePlus