Project description:Using standard morphometric methods and gene expression profiling with a DNA microarray, we explored the impacts of high CO2 conditions on development of the sea urchin, Lytechinus pictus, a pelagic larvae that forms a calcium carbonate endoskeleton. Larvae were raised from fertilization to pluteus stage in seawater with elevated CO2 conditions based upon IPCC emissions scenarios B1 (540ppm CO2) and A1FI (970ppm CO2).
Project description:Using standard morphometric methods and gene expression profiling with a DNA microarray, we explored the impacts of high CO2 conditions on development of the sea urchin, Lytechinus pictus, a pelagic larvae that forms a calcium carbonate endoskeleton. Larvae were raised from fertilization to pluteus stage in seawater with elevated CO2 conditions based upon IPCC emissions scenarios B1 (540ppm CO2) and A1FI (970ppm CO2). Larval L. pictus were cultured in seawater treated with three different concentrations of CO2. We aerated water in culture chambers with air that had been mixed to different CO2 concentrations chosen from IPCC predictions of future atmospheric CO2 levels (28). The B1 scenario, one of the most optimistic, predicts a stabilization of atmospheric CO2 levels at ~540 ppm by 2100, and the A1F1 scenario, which, reflecting a more âbusiness as usualâ scenario, predicts atmospheric CO2 levels of ~970 ppm by 2100. Compressed air (~380 ppm CO2) was used as a control condition. The culture chambers were 20 L buckets medified to allow aeration bubbles of the experimental gas to mix with and gently stir the culture water without contacting the larvae. Replacement seawater (0.35 μm filtered) was added at a constant rate of 0.5 L hr-1. Water pH of each chamber was monitored daily using a Radiometer Analytical PHM240 pH meter. Adult L. pictus were maintained in flowing seawater at ambient temperature (~15-18 ºC) and fed kelp until use. Spawning was induced by coelomic injection of 0.5 M KCl, and eggs were collected in 0.35 μm-filtered seawater. Eggs from 5 females were combined in approximately equal concentrations. Sperm from a single male was collected in the same way, diluted with filtered seawater and added to the egg mixture; thus, all the larvae are half-siblings. Immediately following fertilization, embryos were split into 12 culture chambers providing four replicates of the three CO2 treatments. At the 48 hour time point, a sample of 40,000 larvae was removed from each of the 8 cultures in the 380 and 970 ppm treatments and stored in1 mL Trizol at -80 ºC for later RNA analysis. The larval cDNA samples from each treatment were competitively hybridized on each microarray following a balanced incomplete block design (BIBD) with respect to the assignment of treatments to arrays. In this way, differential expression between all pairs of treatments is estimated with equal precision. Although dye swaps of technical replicates were not used, treatment and dye effects are orthogonal to one another, i.e. treatment effects can be estimated independently of dye effects.
Project description:Here we present LC-MS/MS proteomic datasets of Heliocidaris erythrogramma, Heliocidaris tuberculata, and Lytechinus variegatus eggs and larvae. We find dramatic proteomic differences likely associated with life history evolution and between developmental stages. This study provides a complimentary dataset to previous transcriptomic analyses of the same three sea urchin species.
Project description:Using scRNA-seq coupled with computational approaches, we studied transcriptional changes in cell states of sea urchin embryos during development to the larval stage. Eighteen closely spaced time points were taken during the first 24 hours of development of Lytechinus variegatus (Lv). Developmental trajectories were constructed using Waddington-OT, a computational approach to "stitch" together developmental timepoints. Skeletogenic and primordial germ cell trajectories diverged early in cleavage. Ectodermal progenitors were distinct from other lineages by sixth cleavage, though a small percentage of ectoderm cells briefly co-expressed endoderm markers indicating an early ecto-endoderm cell state, likely in cells originating from the equatorial region of the egg. Endomesoderm cells originated at 6th cleavage also and this state persisted for more than two cleavages, then diverged into distinct endoderm and mesoderm fates asynchronously, with some cells retaining an intermediate specification status until gastrulation. 79 of 80 genes (99%) examined, and included in published developmental gene regulatory networks (dGRNs), are present in the Lv-scRNA-seq dataset, and expressed in the correct lineages in which the dGRN circuits operate.