Ultraviolet radiation (UVR) has a wide range of damaging effects including tissue damage, DNA mutation, and lifespan reduction in aquatic organisms. Some pigmented zooplankton have demonstrated increased resistance to UVR. Pigmented bdelloid rotifers occur in rock pools located in El Paso Co., TX. In this habitat, bdelloids are exposed to an average UVB intensities of 355µW/cm2 during the summer months, and often experience desiccation. They are capable of surviving long periods of desiccation in a UVR-resistant, dormant stage(xerosome). As cellular damage from UVR occurs, certain genes may be up/downregulated to prevent further damage. We hypothesized that increased expression will be detected in genes that aid in repairing UVR induced damage, and that this expression will be UVR dose-dependent. Gene expression was quantified using RNASeq. RNA was extracted using a modified Trizol protocol after a 2hr UVR exposure at four doses (n=5): 0 (control), 130 (low), 370 (mid) or 500 (high) µW/cm2. RNA was then sequenced on an Illumina NextSeq500 and analyzed using the Trinity pipeline. Transcripts were identified from using Blast2Go. Expression of UVR responsive genes was compiled, normalized, and displayed as a heat map. Venn diagrams will be used to highlight the overlap genes up- or down-regulated among treatments.
Results/Conclusions
Transcripts from all exposure treatments were used to create a preliminary de novo transcriptome. More than 62,000 unique transcripts were expressed in bdelloids during the experiment. The three UVR treatments were compared to the control to determine which genes were differentially expressed following UVR exposure. Over 290 of the genes identified were related to UVR response. These genes include: glutathione, glutathione peroxidase, glutathione reductase, glutathione S-transferase; as well as, superoxide dismutase, cytosolic abundant heat soluble, mitochondrial abundant heat soluble, secreted abundant heat soluble, and ultraviolet damage endonuclease, to name a few. More transcripts were upregulated in UVR treatments as compared to the control. A dose-dependent pattern was not observed in the preliminary analyses; however, some clusters of genes are differentially expressed among treatments. Results obtained in this study will enhance our understanding of which bdelloid genes respond to varying levels of UVR induced damage. These data will also create a framework for constructing a general transcriptome for bdelloid rotifers.