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The diatom-derived aldehyde decadienal affects life cycle transition in the ascidian Ciona intestinalis through nitric oxide/ERK signalling.

Castellano I, Ercolesi E, Romano G, Ianora A, Palumbo A - Open Biol (2015)

Bottom Line: PUAs, including 2,4-trans-decadienal (DD), induce deleterious effects on embryonic and larval development of several planktonic and benthic organisms.DD affects redox balance by reducing total glutathione and NO levels.By biochemical and quantitative gene expression analysis, we identify the NO-signalling network affected by DD, including the upregulation of ERK phosphatase mkp1 and consequent reduction of ERK phosphorylation, with final changes in the expression of downstream ERK target genes.

View Article: PubMed Central - PubMed

Affiliation: Stazione Zoologica Anton Dohrn, Villa Comunale, 80121 Naples, Italy.

ABSTRACT
Polyunsaturated aldehydes (PUAs) are fatty-acid-derived metabolites produced by some microalgae, including different diatom species. PUAs are mainly produced as a wound-activated defence mechanism against microalgal predators or released from senescent cells at the end of a bloom. PUAs, including 2,4-trans-decadienal (DD), induce deleterious effects on embryonic and larval development of several planktonic and benthic organisms. Here, we report on the effects of DD on larval development and metamorphosis of the ascidian Ciona intestinalis. Ciona larval development is regulated by the cross-talking of different molecular events, including nitric oxide (NO) production, ERK activation and caspase 3-dependent apoptosis. We report that treatment with DD at the competence larval stage results in a delay in metamorphosis. DD affects redox balance by reducing total glutathione and NO levels. By biochemical and quantitative gene expression analysis, we identify the NO-signalling network affected by DD, including the upregulation of ERK phosphatase mkp1 and consequent reduction of ERK phosphorylation, with final changes in the expression of downstream ERK target genes. Overall, these results give new insights into the molecular pathways induced in marine organisms after exposure to PUAs during larval development, demonstrating that this aldehyde affects key checkpoints of larval transition from the vegetative to the reproductive life stage.

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Related in: MedlinePlus

Gene regulation in response to decadienal (DD) treatment at different times of larval development. Histograms show the differences in expression levels of analysed genes, according to real-time qPCR. Middle larvae incubated with 0.5 μg ml−1 DD were collected after 2, 4 and 6 h. Data are reported as fold differences compared to the control (larvae in seawater without DD; mean ± s.d.). Fold differences equal to or greater than ±2 were considered significant.
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RSOB140182F3: Gene regulation in response to decadienal (DD) treatment at different times of larval development. Histograms show the differences in expression levels of analysed genes, according to real-time qPCR. Middle larvae incubated with 0.5 μg ml−1 DD were collected after 2, 4 and 6 h. Data are reported as fold differences compared to the control (larvae in seawater without DD; mean ± s.d.). Fold differences equal to or greater than ±2 were considered significant.

Mentions: We have previously demonstrated that the endogenous modulation of NO levels in Ciona larvae affects the rate of metamorphosis [29]. In order to understand if NO mediates the response of the larvae to the toxin, we measured NO levels in Ciona larvae treated with the sublethal concentration of 0.5 µg ml−1 DD. NO levels significantly decreased after different times of DD treatment (figure 2). To understand if the change in NO levels was related to the fine regulation of redox homeostasis in response to DD, we first analysed the expression patterns of some genes involved in redox homeostasis. These genes were identified by in silico analysis of the Ciona genome and are reported in table 1. These genes include those coding for manganese superoxide dismutase (Mn-SOD), a key enzyme involved in the scavenging of reactive oxygen species [36,37], NO synthase (NOS), responsible for NO synthesis [26,38], two enzymes responsible for GSH synthesis, the glutamate–cysteine ligase regulatory subunit (gclm) and GSH synthase (gss) [32,33], glutaredoxin-1 (glrx) involved in GSH reduction [32,33], gamma-glutamyl tranpeptidase (ggt) involved in GSH metabolism and recycling [39,40], and GSH S-transferase (gstm), which catalyses the conjugation of GSH to xenobiotic substrates for detoxification [32,33]. The relative expression of all these genes was followed by real-time qPCR experiments, after treating middle larvae (20–21 hpf) with 0.5 µg ml−1 DD (figure 3) and collecting them after 2, 4 and 6 h of treatment. The expression of gclm and ggt progressively increased at all hours tested, whereas the expression of the other genes, including NOS, was unaffected. These results prompted us to measure total GSH levels in larvae treated with DD. A significant reduction in total GSH levels was observed after 2 h treatment (figure 4), whereas thereafter, GSH levels were comparable to the controls.Figure 2.


The diatom-derived aldehyde decadienal affects life cycle transition in the ascidian Ciona intestinalis through nitric oxide/ERK signalling.

Castellano I, Ercolesi E, Romano G, Ianora A, Palumbo A - Open Biol (2015)

Gene regulation in response to decadienal (DD) treatment at different times of larval development. Histograms show the differences in expression levels of analysed genes, according to real-time qPCR. Middle larvae incubated with 0.5 μg ml−1 DD were collected after 2, 4 and 6 h. Data are reported as fold differences compared to the control (larvae in seawater without DD; mean ± s.d.). Fold differences equal to or greater than ±2 were considered significant.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4389792&req=5

RSOB140182F3: Gene regulation in response to decadienal (DD) treatment at different times of larval development. Histograms show the differences in expression levels of analysed genes, according to real-time qPCR. Middle larvae incubated with 0.5 μg ml−1 DD were collected after 2, 4 and 6 h. Data are reported as fold differences compared to the control (larvae in seawater without DD; mean ± s.d.). Fold differences equal to or greater than ±2 were considered significant.
Mentions: We have previously demonstrated that the endogenous modulation of NO levels in Ciona larvae affects the rate of metamorphosis [29]. In order to understand if NO mediates the response of the larvae to the toxin, we measured NO levels in Ciona larvae treated with the sublethal concentration of 0.5 µg ml−1 DD. NO levels significantly decreased after different times of DD treatment (figure 2). To understand if the change in NO levels was related to the fine regulation of redox homeostasis in response to DD, we first analysed the expression patterns of some genes involved in redox homeostasis. These genes were identified by in silico analysis of the Ciona genome and are reported in table 1. These genes include those coding for manganese superoxide dismutase (Mn-SOD), a key enzyme involved in the scavenging of reactive oxygen species [36,37], NO synthase (NOS), responsible for NO synthesis [26,38], two enzymes responsible for GSH synthesis, the glutamate–cysteine ligase regulatory subunit (gclm) and GSH synthase (gss) [32,33], glutaredoxin-1 (glrx) involved in GSH reduction [32,33], gamma-glutamyl tranpeptidase (ggt) involved in GSH metabolism and recycling [39,40], and GSH S-transferase (gstm), which catalyses the conjugation of GSH to xenobiotic substrates for detoxification [32,33]. The relative expression of all these genes was followed by real-time qPCR experiments, after treating middle larvae (20–21 hpf) with 0.5 µg ml−1 DD (figure 3) and collecting them after 2, 4 and 6 h of treatment. The expression of gclm and ggt progressively increased at all hours tested, whereas the expression of the other genes, including NOS, was unaffected. These results prompted us to measure total GSH levels in larvae treated with DD. A significant reduction in total GSH levels was observed after 2 h treatment (figure 4), whereas thereafter, GSH levels were comparable to the controls.Figure 2.

Bottom Line: PUAs, including 2,4-trans-decadienal (DD), induce deleterious effects on embryonic and larval development of several planktonic and benthic organisms.DD affects redox balance by reducing total glutathione and NO levels.By biochemical and quantitative gene expression analysis, we identify the NO-signalling network affected by DD, including the upregulation of ERK phosphatase mkp1 and consequent reduction of ERK phosphorylation, with final changes in the expression of downstream ERK target genes.

View Article: PubMed Central - PubMed

Affiliation: Stazione Zoologica Anton Dohrn, Villa Comunale, 80121 Naples, Italy.

ABSTRACT
Polyunsaturated aldehydes (PUAs) are fatty-acid-derived metabolites produced by some microalgae, including different diatom species. PUAs are mainly produced as a wound-activated defence mechanism against microalgal predators or released from senescent cells at the end of a bloom. PUAs, including 2,4-trans-decadienal (DD), induce deleterious effects on embryonic and larval development of several planktonic and benthic organisms. Here, we report on the effects of DD on larval development and metamorphosis of the ascidian Ciona intestinalis. Ciona larval development is regulated by the cross-talking of different molecular events, including nitric oxide (NO) production, ERK activation and caspase 3-dependent apoptosis. We report that treatment with DD at the competence larval stage results in a delay in metamorphosis. DD affects redox balance by reducing total glutathione and NO levels. By biochemical and quantitative gene expression analysis, we identify the NO-signalling network affected by DD, including the upregulation of ERK phosphatase mkp1 and consequent reduction of ERK phosphorylation, with final changes in the expression of downstream ERK target genes. Overall, these results give new insights into the molecular pathways induced in marine organisms after exposure to PUAs during larval development, demonstrating that this aldehyde affects key checkpoints of larval transition from the vegetative to the reproductive life stage.

Show MeSH
Related in: MedlinePlus