Lavenders defensive properties explored
Lavender is instantly recognisable with its heady scent and distinctive purple flowers. The plant is cultivated as an ornamental, for use as a culinary herb, and commercially for the production of essential oils that have numerous cosmetic and medicinal applications. Now, new research published in the Journal Plant Molecular Biology is exploring the plant's ability to create natural pesticides.
The research was led by Soheil Mahmoud, an associate professor of biology at the University of British Columbia. Soheil conducts research on organic compounds found in plants and has a specific interest in lavender. While lavender is known for its strong scent, and the plant's oils are said to have a healing, or soothing benefit, Mahmoud says lavender has much more to offer.
"Lavender has proven to be very good at protecting itself through production of antimicrobial and anti-fungal biochemical compounds," says Mahmoud. "One of our goals is to identify molecules that are involved in this natural self-defence."
Using a research field at UBC's Okanagan campus, Mahmoud and his research group are attempting to identify, characterise and clone the specific genes that control the defensive properties of lavender. If this is indeed possible, Mahmoud suggests this may have significant environmental implications.
Lavenders produce essential oils, he explains, and these consist mainly of organic compounds, including a potent antimicrobial and insecticidal monoterpene named 3-carene. In the latest research, the team of scientists isolated and functionally characterised the gene - methyl jasmonate (MeJA) responsive monoterpene synthase (Li3CARS) - responsible for 3-carene synthesis in the hybrid Lavandula x intermedia. The gene was cloned into an E.coli expression vector and was demonstrated to preferentially convert Geranyl diphosphate – a precursor of monoterpenes – into 3-carene. Neryl phosphate was also demonstrated to be an accepted precursor although levels of 3-carene production were 10-fold less.
The team then carried out a transcriptional analysis of leaf and flower tissue, finding Li3CARS to be expressed at much higher levels in leaves compared to flowers. Furthermore, expression of the gene was upregulated when the plant was treated with Methyl Jasmonate – a defensive compound produced in response to biotic and abiotic stress. Together the results suggest an important role for Li3CARSin plant defence.
Traditionally, chemical herbicides or pesticides have been used to control fungal growth or pests like insects. But Mahmoud says this method is becoming less and less desirable as many of the pests and fungi have become resilient to the chemicals used, and as consumers prefer food that is untreated or treated with "natural" pesticides.
"We've become much more health conscious," he says. "There are healthier options instead of spraying chemicals on plants; we just need to explore these. Aromatic plants like lavenders could provide suitable alternatives to chemical-based insecticides"
Subscribers to Horticultural Science can access more research on how natural products from lavender can be used in crop protection. For example, using the search string "lavandula" AND "essential oils" AND ("fungicides" OR "pesticides" OR "insecticides") returns over 100 results, a selection is given in the further reading.
Reference
Adal AM, Sarker LS, Lemke AD, Mahmoud SS, 2017. Isolation and functional characterization of a methyl jasmonate-responsive 3-carene synthase from Lavandula x intermedia. Plant Molecular Biology; 93 (6): 641 DOI: 10.1007/s11103-017-0588-6