Unknown,Transcriptomics,Genomics,Proteomics

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Widespread transcriptional changes preempt the critical pelagic-benthic transition in the vetigastropod Haliotis asinina

ABSTRACT: Larval settlement and metamorphosis is a vital transition period for marine invertebrates and can have far-reaching effects on the ecology and evolution of a species. To explore the molecular mechanisms of this critical process in a non-model organism, the tropical abalone Haliotis asinina, we employed cDNA microarray methods. By comparing gene expression profiles through mid to late larval development and metamorphosis, we identified 144 genes as likely candidates for a role in competence and/or metamorphosis. Gene characterization showed that ~60% of these were significantly similar to previously described genes from other taxa, while ~40% had no significant similarities to any known genes. A high 49.3% of genes were gastropod- or abalone-specific, but none appear to be Lophotrochozoan-specific, despite the fact that metamorphosis is thought to have had a separate origin in this group. Based on temporal expression profiles, the differentially expressed larval and postlarval genes can be clustered into 5 categories that reveal there are strikingly different transcriptional patterns occurring during this phase of development. Some classes of gene activation are contingent upon exogenous cues and correlate with the initiation of settlement and metamorphosis. Importantly, there is also extensive gene activity associated with the endogenous attainment of competence, which occurs prior to, and independent of, the exogenous induction of settlement. Our results show that as the haliotid veliger larva matures, it requires the coordinated regulation of temporally different batteries of genes involved in a wide range of physiological and developmental processes associated with colonisation of the benthos. Although the signalling pathways operating at metamorphosis may be conserved across the animal kingdom, it appears they are regulating the expression of novel genes specific to abalone, gastropods and molluscs during H. asinina metamorphosis. Keywords: timecourse; metamorphosis; marine ecology Each microarray slide contained a different combination of 2 of the 9 developmental stages used in the experiment (66 hpf, 78 hpf, 90 hpf, 108 hpf, 120 hpf, 144 hpf, 12 hpi, 24 hpi, 48 hpi). Each developmental stage was subjected to 4 hybridisations â amounting to 4 technical replicates per stage - in a loop design (Churchill 2002; Oleksiak et al. 2002). This design led to raw data consisting of 72 measurements - 9 stages with 8 replicates (including 2 replicates per chip) - for each of 5541 spots.

ORGANISM(S): Haliotis asinina

SUBMITTER: Elizabeth Williams

PROVIDER: E-GEOD-13039 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:In zebrafish, vitellogenic oocytes can incorporate significant amounts of 17β-estradiol released from nearby granulosa cells according to a first-order kinetics, since the steroid low polarity ensures high permeability and affinity for yolk lipids. Estrogen bioactivity is likely, because the maternal mRNA for the estrogen receptor-β2 (ers2a) is highly expressed in ovulated oocytes. This transcript is available for translation in the embryo until its sharp decline from 4 to 8 hours post-fertilization (hpf), being replaced by low levels of zygotic ers2a mRNA from 24 hpf to hatching at 48 hpf, as determined by qRT-PCR. Estrogen receptors-α and -β1 are only expressed zygotically at low levels from 24 hpf onwards. To test the functional role of maternal ers2a mRNA, 1- or 2-cell embryos were injected with 10.3 ng each of morpholino to knockdown translation (MO2-ers2a) of both maternal and zygotic ers2a transcripts, missplicing morpholino (MO3-ers2a) to block post-transcriptionally the zygotic transcript alone, and a nonspecific morpholino (MO-control) as a control. Treatment with MO2-ers2a caused severe malformations in 63% of 1-5 dpf larvae, as compared to 10-11% in those treated with MO3-ers2a and MO2-control. Defects included body growth delay and curved shape, abnormal brain and splanchnocranium development, enlarged and hemorrhagic pericardial cavity, uninflated swim bladder and rudimentary caudal fin with aberrant circular motion. Affected larvae could survive for only 12-14 days. Co-injection of an anti-p53 MO failed to rescue the MO2-ers2a-phenotypes, eliminating the possibility of off-target effects. Pangenomic microarray analysis revealed that 240 and 219 significantly expressed transcripts were up- and down-regulated, respectively, by maternal Ers2a protein deficiency in 8-hpf MO2-ers2a-embryos. Also at 48 hpf, 162 and 120 presumably zygotic transcripts were up- and down-regulated, respectively, but only 18 were in common with each of the 8-hpf sets. Whole-mount in situ hybridization revealed an intensified expression of the genes six3.1 and emx1 in MO2-ers2a-embryos at 24-48 hpf, as compared to controls. These findings suggest the involvement of maternal ers2a mRNA in the epigenetic programming of zebrafish development. MO2-ers2a morphants were compared with MO-control at 8 hpf and 48 hpf. MO2-ers2a is a morpholinos selected to knockdown translation of ers2a mRNA

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Widespread transcriptional changes preempt the critical pelagic-benthic transition in the vetigastropod Haliotis asinina

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