DISSERTATION RESEARCH: Systematics, host-specificity, and genome evolution of holoparasitic plants: A case study in Orobanche (Orobanchaceae)

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

Parasitism is a unique life history strategy that has evolved independently dozens of times in plants, animals, and other organisms. Due to its high biodiversity and a good understanding of its mode of parasitism, the non-photosynthetic parasitic plant genus Orobanche provides a remarkable opportunity for understanding the unique macro- and microevolutionary consequences of parasitism in a phylogenetic framework. Recent work has identified both evolutionary and genetic consequences, including numerous host specific lineages as well as host-to-parasite horizontal gene transfer. This research will use genomic-scale sequencing of new-world Orobanche and field studies across North America to develop the following: (1) a fine-scale understanding of tempo and mode of genome evolution in parasitic plants, (2) a better understanding of host-breadth, and (3) abiotic and biotic habitat characteristics, with a taxonomic revision to follow. In addition to advancing the fields of evolutionary biology and ecology, an improved understanding of host specificity and parasite genomics may be of use in combating several species of Orobanche that cause severe agricultural damage to tomato, sunflower, and other crops in Europe, Asia, and the Americas. One graduate and several undergraduate students will receive training in laboratory and museum research techniques, and will have the opportunity to present the results at regional and national meetings. Specifically, we will use a genome skimming approach, coupled with field studies across North America to study (1) fine-scale tempo and mode of plastid and mitochondrial evolution in new-world Orobanche, (2) host-breadth of numerous lineages, (3) abiotic and biotic habitat characteristics to better understand distributions, and (4) diagnosable features of lineages, leading directly to taxonomic revision. Out of several genome reduction techniques available, genome-skimming (whole-genome shotgun sequencing) will provide the most cost-effective way to
capture the high-copy fraction of genomic DNA, including the
nuclear ribosomal cistron, plastome, and mitogenome, even from degraded material such as that found on herbarium sheets.