High‐affinity nitrate transporters are considered to be the major transporter system for nitrate uptake in diatoms. In the diatom genus
The salinity gradient separating marine and freshwater environments represents a major ecological divide for microbiota, yet the mechanisms by which marine microbes have adapted to and ultimately diversified in freshwater environments are poorly understood. Here, we take advantage of a natural evolutionary experiment: the colonization of the brackish Baltic Sea by the ancestrally marine diatom Skeletonema marinoi. To understand how diatoms respond to low salinity, we characterized transcriptomic responses of acclimated S. marinoi grown in a common garden. Our experiment included eight strains from source populations spanning the Baltic Sea salinity cline. Gene expression analysis revealed that low salinities induced changes in the cellular metabolism of S. marinoi, including upregulation of photosynthesis and storage compound biosynthesis, increased nutrient demand, and a complex response to oxidative stress. However, the strain effect overshadowed the salinity effect, as strains differed significantly in their response, both regarding the strength and the strategy (direction of gene expression) of their response. The high degree of intraspecific variation in gene expression observed here highlights an important but often overlooked source of biological variation associated with how diatoms respond to environmental change.
more » « less- Award ID(s):
- 1651087
- NSF-PAR ID:
- 10368055
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- The ISME Journal
- Volume:
- 16
- Issue:
- 7
- ISSN:
- 1751-7362
- Format(s):
- Medium: X Size: p. 1776-1787
- Size(s):
- ["p. 1776-1787"]
- Sponsoring Org:
- National Science Foundation
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Skeletonema , three forms of genes encoding high‐affinity nitrate transporters (NRT 2NRT 2Skeletonema species:S. dohrnii ,S. menzelii, andS. marinoi . Primers were developed for eachNRT 2RT ‐PCR was performed. For eachNRT 2Skeletonema species had similar transcriptional patterns. The transcript levels ofNRT 2:1NRT 2:2NRT 2:3NRT 2Skeletonema . The differentialNRT 2 -
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High‐affinity nitrate transporters are considered to be the major transporter system for nitrate uptake in diatoms. In the diatom genus Skeletonema, three forms of genes encoding high‐affinity nitrate transporters (NRT2) were newly identified from transcriptomes generated as part of the marine microbial eukaryote transcriptome sequencing project. To examine the expression of each form of NRT2 under different nitrogen environments, laboratory experiments were conducted under nitrate‐sufficient, ammonium‐sufficient, and nitrate‐limited conditions using three ecologically important Skeletonema species: S. dohrnii, S. menzelii, and S. marinoi. Primers were developed for each NRT2 form and species and Q‐RT‐PCR was performed. For each NRT2 form, the three Skeletonema species had similar transcriptional patterns. The transcript levels of NRT2:1 were significantly elevated under nitrogen‐limited conditions, but strongly repressed in the presence of ammonium. The transcript levels of NRT2:2 were also repressed by ammonium, but increased 5‐ to 10‐fold under nitrate‐sufficient and nitrogen‐limited conditions. Finally, the transcript levels of NRT2:3 did not vary significantly under various nitrogen conditions, and behaved more like a constitutively expressed gene. Based on the observed transcript variation among NRT2 forms, we propose a revised model describing nitrate uptake kinetics regulated by multiple forms of nitrate transporter genes in response to various nitrogen conditions in Skeletonema. The differential NRT2 transcriptional responses among species suggest that species‐specific adaptive strategies exist within this genus to cope with environmental changes.more » « less
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