Project description:Prymnesium parvum is regarded as one of the most notorious harmful algal bloom (HAB) species worldwide. In recent years, it has frequently formed toxic blooms in coastal and brackish waters of America, Europe, Australia, Africa and Asia, causing large-scale mortalities of wild and cultured fish and other gill-breathing animals. In the last decade, blooms of P. parvum have expanded to inland fresh waters in the USA, presumably due to changes in environmental conditions. The aim of the experiment was to establish the gill transcriptomic responses to P. parvum in rainbow trout. We used 2 different concentrations of P. parvum and identified fish with low and moderate responses to the algae. Based on the dose of and the fish response, fish were classified into 4 groups with high exposure/moderate response (HM), high exposure/low response (HL), low exposure/low response (LL) and control group (C) with no exposure/no response. Gene expression profiling of the gill tissue was performed using a microarray platform developed and validated for rainbow trout.
Project description:<p>Harmful algal blooms (HABs) of the toxic haptophyte <em>Prymnesium parvum</em> are a recurrent problem in many inland and estuarine waters around the world. Strains of <em>P. parvum</em> vary in the toxins they produce and in other physiological traits associated with HABs, but the genetic basis for this variation is unknown. To investigate genome diversity in this morphospecies, we generated genome assemblies for 15 phylogenetically and geographically diverse strains of <em>P. parvum</em> including Hi-C guided, near-chromosome level assemblies for 2 strains. Comparative analysis revealed considerable DNA content variation between strains, ranging from 115 to 845 Mbp. Strains included haploids, diploids and polyploids, but not all differences in DNA content were due to variation in genome copy number. Haploid genome size between strains of different chemotypes differed by as much as 243 Mbp. Syntenic and phylogenetic analyses indicate that UTEX 2797, a common laboratory strain from Texas, is a hybrid that retains 2 phylogenetically distinct haplotypes. Investigation of gene families variably present across strains identified several functional categories associated with metabolic and genome size variation in <em>P. parvum</em> including genes for the biosynthesis of toxic metabolites and proliferation of transposable elements. Together, our results indicate that <em>P. parvum</em> is comprised of multiple cryptic species. These genomes provide a robust phylogenetic and genomic framework for investigations into the eco-physiological consequences of the intra- and inter-specific genetic variation present in <em>P. parvum</em> and demonstrate the need for similar resources for other HAB-forming morphospecies.</p>
