Establishing genome sequencing and assembly for non-model and emerging model organisms: a brief guide.

Reference genome assemblies are the basis for comprehensive genomic analyses and comparisons. Due to declining sequencing costs and growing computational power, genome projects are now feasible in smaller labs. De novo genome sequencing for non-model or emerging model organisms requires knowledge about genome size and techniques for extracting high molecular weight DNA. Next to quality, the amount of DNA obtained from single individuals is crucial, especially, when dealing with small organisms. While long-read sequencing technologies are the methods of choice for creating high quality genome assemblies, pure short-read assemblies might bear most of the coding parts of a genome but are usually much more fragmented and do not well resolve repeat elements or structural variants. Several genome initiatives produce more and more non-model organism genomes and provide rules for standards in genome sequencing and assembly. However, sometimes the organism of choice is not part of such an initiative or does not meet its standards. Therefore, if the scientific question can be answered with a genome of low contiguity in intergenic parts, missing the high standards of chromosome scale assembly should not prevent publication. This review describes how to set up an animal genome sequencing project in the lab, how to estimate costs and resources, and how to deal with suboptimal conditions. Thus, we aim to suggest optimal strategies for genome sequencing that fulfil the needs according to specific research questions, e.g. "How are species related to each other based on whole genomes?" (phylogenomics), "How do genomes of populations within a species differ?" (population genomics), "Are differences between populations relevant for conservation?" (conservation genomics), "Which selection pressure is acting on certain genes?" (identification of genes under selection), "Did repeats expand or contract recently?" (repeat dynamics).