About This Project

Joshua trees are perhaps the strangest plants in the world. Their long, spindly branches form twisted candelabras that have become an iconic image of the western American landscape. Ecological modeling suggests that global warming could drive Joshua trees to extinction. We propose to sequence the Joshua tree genome. This powerful research tool will help identify genes that have allowed Joshua trees to adapt to desert environments, and which could help them survive climate change.

Ask the Scientists

What is the context of this research?

A keystone species of the Mojave Desert, Joshua trees provide habitat for many other species, and there are numerous state and National Parks dedicated to their preservation. Unfortunately, ecological modeling suggests that, due to global warming, many populations are likely to go extinct.

Recent advances in DNA sequencing technology have made it possible to cheaply and efficiently generate genome sequence data. This makes it possible to explore the genetic bases of many features in many different organisms. We will use the Joshua tree genome to identify genes that allow Joshua trees to survive extreme environments. This will inform management strategies to help Joshua tree populations persist in the the face of climate change.

What is the significance of this project?

The Mojave Desert contains the hottest and driest regions of North America. To survive in these inhospitable environments, Joshua trees have developed many physiological adaptations. Sequencing the Joshua tree genome will reveal the genetic basis of these adaptations, and identify strains that may allow Joshua trees to adapt to climate change.

Also, Joshua trees rely on yucca moths for pollination. The moths actively pollinate the trees and lay eggs in the flowers. The eggs become caterpillars that eat some of the seeds. So, the trees pay for pollination by sacrificing seeds to the moths’ larvae. Joshua tree flowers are adapted to promote pollination while limiting the number of seeds that get eaten. Sequencing the genome will identify genes involved in coevolution with yucca moths.

What are the goals of the project?

This project is the first stage in an effort to completely sequence the Joshua tree genome. Ultimately we hope to produce a completed, assembled and annotated reference genome sequence. This phase of the project will involve shotgun sequencing on an Illumina HiSeq platform. This process will produce about 700 million snippets of DNA sequence data. These data will provide useful baseline information about the Joshua tree genome, such as the total amount of genetic variation (heterozygosity), and how much of the genome is composed of large repetitive regions. The data will also be used to complement sequencing to be generated in the next phases of the project, which will involve PacBio sequencing, BioNano optical mapping, and reference based annotation using RNA-seq.