Gill transcriptome response to changes in environmental calcium in the green spotted puffer fish.
BACKGROUND
Calcium ion is tightly regulated in body fluids and for euryhaline fish, which are exposed to rapid changes in environmental [Ca2+], homeostasis is especially challenging. The gill is the main organ of active calcium uptake and therefore plays a crucial role in the maintenance of calcium ion homeostasis. To study the molecular basis of the short-term responses to changing calcium availability, the whole gill transcriptome obtained by Super Serial Analysis of Gene Expression (SuperSAGE) of the euryhaline teleost green spotted puffer fish, Tetraodon nigroviridis, exposed to water with altered [Ca2+] was analysed.


RESULTS
Transfer of T. nigroviridis from 10 ppt water salinity containing 2.9 mM Ca2+ to high (10 mM Ca2+ ) and low (0.01 mM Ca2+) calcium water of similar salinity for 2-12 h resulted in 1,339 differentially expressed SuperSAGE tags (26-bp transcript identifiers) in gills. Of these 869 tags (65%) were mapped to T. nigroviridis cDNAs or genomic DNA and 497 (57%) were assigned to known proteins. Thirteen percent of the genes matched multiple tags indicating alternative RNA transcripts. The main enriched gene ontology groups belong to Ca2+ signaling/homeostasis but also muscle contraction, cytoskeleton, energy production/homeostasis and tissue remodeling. K-means clustering identified co-expressed transcripts with distinct patterns in response to water [Ca2+] and exposure time.


CONCLUSIONS
The generated transcript expression patterns provide a framework of novel water calcium-responsive genes in the gill during the initial response after transfer to different [Ca2+]. This molecular response entails initial perception of alterations, activation of signaling networks and effectors and suggests active remodeling of cytoskeletal proteins during the initial acclimation process. Genes related to energy production and energy homeostasis are also up-regulated, probably reflecting the increased energetic needs of the acclimation response. This study is the first genome-wide transcriptome analysis of fish gills and is an important resource for future research on the short-term mechanisms involved in the gill acclimation responses to environmental Ca2+ changes and osmoregulation.
Pinto
Patrícia Is
PI
Centro de Ciências do Mar, CIMAR-Laboratório Associado, University of Algarve, Campus de Gambelas, 8005-139 Faro, Portugal. acanario@ualg.pt
Matsumura
Hideo
H
Thorne
Michael As
MA
Power
Deborah M
DM
Terauchi
Ryohei
R
Reinhardt
Richard
R
Canário
Adelino Vm
AV
D000818:Animals; D002118:Calcium / Q000097:blood / Q000494:pharmacology*; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism; D016000:Cluster Analysis; D004247:DNA / Q000235:genetics; D030541:Databases, Genetic; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics; D004777:Environment; D020224:Expressed Sequence Tags; D029941:Fish Proteins / Q000235:genetics / Q000378:metabolism; D020869:Gene Expression Profiling; D015723:Gene Library; D005880:Gills / Q000187:drug effects* / Q000378:metabolism*; D058977:Molecular Sequence Annotation; D010858:Pigmentation / Q000187:drug effects / Q000235:genetics*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D023721:Tetraodontiformes / Q000097:blood / Q000235:genetics*; D013997:Time Factors; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics; D014867:Water / Q000737:chemistry
D015220:Calcium Channels; D029941:Fish Proteins; D012333:RNA, Messenger; D014867:Water; D004247:DNA; D002118:Calcium