title: Effects of cadmium exposure on sea urchin development assessed by SSH and RT-qPCR: metallothionein genes and their differential induction.
abstract: In order to study the defense strategies activated by Paracentrotus lividus embryos in response to sub-lethal doses of CdCl2, we compared the induced transcripts to that of control embryos by suppression subtractive hybridization technique. We isolated five metallothionein (MT) cDNAs and other genes related to detoxification, to signaling pathway components, to oxidative, reductive and conjugative biotransformation, to RNA maturation and protein synthesis. RT-qPCR analysis revealed that two of the five P. lividus MT (PlMT7 and PlMT8) genes appeared to be constitutively expressed and upregulated following cadmium treatment, whereas the other three genes (PlMT4, PlMT5, PlMT6) are specifically switched-on in response to cadmium treatment. Moreover, we found that this transcriptional induction is concentration dependent and that the cadmium concentration threshold for the gene activation is distinct for every gene. RT-qPCR experiments showed in fact that, among induced genes, PlMT5 gene is activated at a very low cadmium concentration (0.1 μM) whereas PlMT4 and PlMT6 are activated at intermediate doses (1-10 μM). Differently, PlMT7 and PlMT8 genes increase significantly their expression only in embryos treated with the highest dose (100 μM CdCl2). We found also that, in response to a lethal dose of cadmium (1 μM), only PlMT5 and PlMT6 mRNA levels increased further. These data suggest a hierarchical and orchestrated response of the P. lividus embryo to overcome differential environmental stressors that could interfere with a normal development.
authors.affiliation: Dipartimento di Scienze e Tecnologie Molecolari e Biomolecolari, Università di Palermo, viale delle Scienze, Ed. 16, 90128, Palermo, Italy. maria.ragusa@unipa.it
authors.forename: Maria Antonietta
authors.initials: MA
authors.lastname: Ragusa
authors.forename: Salvatore
authors.initials: S
authors.lastname: Costa
authors.forename: Marco
authors.initials: M
authors.lastname: Gianguzza
authors.forename: Maria Carmela
authors.initials: MC
authors.lastname: Roccheri
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Gianguzza
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002104:Cadmium / Q000633:toxicity*; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D008668:Metallothionein / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization / Q000379:methods; D010802:Phylogeny; D060888:Real-Time Polymerase Chain Reaction; D012617:Sea Urchins / Q000187:drug effects* / Q000196:embryology / Q000235:genetics*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
chemical_list: D002104:Cadmium; D008668:Metallothionein