An international team of scientists has for the first time mapped the entire genome of the jojoba plant (Simmondsia chinensis).
The jojoba (Simmondsia chinensis) in King Canyon Wash, Saguaro National Park West, Arizona, the United States. Image credit: Katja Schulz / CC BY 2.0.
Jojoba is a dioecious desert shrub native to the Sonoran desert and Baja California regions of North America.
Its seeds contain a liquid wax similar to spermwhale oil (spermaceti) in composition with properties that have numerous cosmetic and industrial uses.
“Jojoba is the only plant to store wax in its seeds. Such a vegetable oil has heretofore been unavailable,” said co-author Dr. Eberhard Munz, a researcher in the Leibniz-Institute of Plant Genetics and Crop Plant Research.
“The liquid wax is usually referred to as jojoba oil. Jojoba oil possesses several advantages over sperm whale oil and is widely used in pharmacy, cosmetics and hair care products.”
“We have microscopic glands in our skin that secrets sebum (waxy matter). Jojoba oil is believed to play the role of sebum. As we age, the glands produce less and less sebum, which results in dry skin and hair.”
“Native Americans used jojoba wax to lubricate skin, whereas Europeans relied on sperm whale products,” added co-author Dr. Ljudmilla Borisjuk, also from the Leibniz-Institute of Plant Genetics and Crop Plant Research.
“As jojoba seeds can accumulate up to 60% seed oil with more than 95% wax esters with no observable germination effects, there is likely much to be learned about how jojoba seeds synthesize, package, and mobilize waxes.”
The scientists extracted and sequenced high-quality genomic DNA from leaves of 3-month-old jojoba plant.
They found that the jojoba genome contains 887 million base pairs of DNA, including 23,490 protein-coding genes.
“Phylogenetic analysis revealed that the jojoba genome is a relatively ancient Astrid genome that has undergone minimal rearrangements, where 1,253 gene families are substantially expanded and 1,783 families are contracted in the jojoba genome compared with other plant genomes,” they said.
“Of the 23,490 jojoba predicted proteins, 18,471 are clustered into 12,486 families, and of these, 9,876 families are shared by five genomes: jojoba, the thale cress (Arabidopsis thaliana), the beet (Beta vulgaris), the physic nut (Jatropha curcas), and the castor bean (Ricinus communis).”
The team also found that jojoba plant diverged from the grape (Vitis vinifera), the cacao tree (Theobroma cacao), and the peach (Prunus persica) approximately 100 million years ago.
“Overall, our results provide a reference-quality genome for jojoba that facilitates the placement of this minimally studied plant species into evolutionary context,” the authors said.
“In addition, these genomic resources enabled insights into a previously unrecognized heterogeneity of neutral lipid synthesis and storage in jojoba seeds.”
“These resources will be valuable to others interested in the utilization of this species as an oilseed crop and will also fill important knowledge gaps for this taxonomically isolated dioecious species and its life history and adaptations.”
The results were published in the journal Science Advances.
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Drew Sturtevant et al. 2020. The genome of jojoba (Simmondsia chinensis): A taxonomically isolated species that directs wax ester accumulation in its seeds. Science Advances 6 (11): eaay3240; doi: 10.1126/sciadv.aay3240
