Format: ORAL

Shengchen Shan1,Bing Yang2,3,Douglas E. Soltis1,4,5

1 Florida Museum of Natural History, University of Florida, Gainesville, USA 2 Division of Plant Sciences, University of Missouri, Columbia, USA 3 Donald Danforth Plant Science Center, St. Louis, USA 4 Department of Biology, University of Florida, Gainesville, USA 5 Genetics Institute, University of Florida, Gainesville, USA

Dynamic genomic changes following polyploidy (i.e., whole-genome duplication; WGD) may contribute to the success of polyploids. At the gene level in allopolyploids, changes include retention of both parental gene copies, function/expression divergence between the two parental copies, and loss/silencing of one parental copy. However, the rules governing these processes remain unclear, limited largely by the absence of study in organisms that best exemplify the earliest stages of WGD. Diploid and polyploid Tragopogon (Asteraceae) represent an excellent natural system to study the immediate consequences following polyploidy. Allotetraploid T. miscellus and T. mirus are 90-100 years old. Functional studies of genes with different retention patterns in young Tragopogon polyploids can be used to elucidate the genetic factors underlying the success of WGD. To accomplish this, we report here on our development and optimization of tissue culture, Agrobacterium-mediated transformation, and a genome editing system in Tragopogon. Using CRISPR/Cas9, we successfully knocked out PDS (encoding phytoene desaturase in carotenoid synthesis) and also DFR (encoding dihydroflavonol 4-reductase in anthocyanin production) in diploid and polyploid Tragopogon. The experiments produced mutants with the expected phenotypes, i.e., albino plants and plants without anthocyanins, respectively. In addition, the CRISPR-mediated genome editing system exhibited high efficiency: in the tetraploid mutants, modifications of all four alleles of the target gene were identified in the T0 generation. With this exceptional toolkit in place, we have proposed functional studies of 12 Tragopogon genes controlling pivotal traits and having specific retention patterns following polyploidy. By following CRISPR-mediated changes in gene retention following WGD, we will examine genes and complex phenotypes associated with meiosis, flower/inflorescence development, and stress response. This established genome editing platform permits functional studies in the evolutionary model system Tragopogon, contributing to a better understanding of the genetic consequences following WGD and the success of polyploids.