Chromosome-Scale Assembly of the Poplar Genome Sequence

The sequencing of the Populus genome is a watershed event for woody perennial research, but the fragmentary nature of the sequenceassembly will inhibit comparative and functional genomics efforts. A chromosome-level assembly would enhance the exceptionalopportunities for comparative genomics between Populus and other model angiosperms with drastically different growth habits and lifehistories, including Arabidopsis and Medicago. The Populus genome has been sequenced to a 8.1X depth, and an initial draft assemblyhas yielded 1028 sequence scaffolds larger than 37 kb and containing 90% of the euchromatic genome. We propose to 1.) use geneticmapping to assemble sequence scaffolds into chromosomal scaffolds, and 2.) use fluorescent in situ hybridization (FISH) to confirmthe assembly and determine chromosomal locations of centromeres, telomeres, and large repeat elements. The resources created fromthe proposed work will support future functional and comparative genomics studies by arranging all genes in Populus into linearassemblies, thus fostering studies of genome evolution, assessments of conserved synteny, and determinations of gene orthology. Thiswill lead to enhanced mechanistic understanding of the processes of adaptation and carbon fixation, thus furthering DOE'sprogrammatic goals of carbon sequestration, phytoremediation, and mitigation of the impacts of climatic change.