Bog myrtle key to sustainable ethylene inhibition

BY ANTHONY KING | 10 APRIL 2024

Collaborative research between Syngenta, UCL and Royal Holloway reveals benefits of Myrica gale.

The bog myrtle (Myrica gale), a hardy shrub growing on European wetlands, has a trick up its sleeve. It exudes a chemical from its fruits and leaves that inhibits seed germination and growth in a range of plant species. Now, research has revealed this chemical, myrigalone A (MyA), is a potent inhibitor of ethylene biosynthesis (Plant Communications, doi: 10.1016/j.xplc.2024.100846).

Ethylene is the key to fruit ripening, but the chemical also has many other effects in plants, such as encouraging root and shoot growth. Inhibiting ethylene production could increase crop survival during drought, block the germination of weeds or slow flower ageing.

The researchers used a special social amoeba, Dictyostelium discoideum, to investigate the bog myrtle chemical. ‘When we treat amoeba with the compound, it blocks ethylene production,’ says Robin Williams at Royal Holloway University of London, who led the team, which included researchers at UCL and Syngenta. The amoeba could no longer produce a fruiting body.

The compound also blocked the germination of rye, wheat and barley seeds in lab experiments. The team investigated its mechanism by creating a library of mutant amoeba and growing them with MyA.

‘In one of these mutants, the target of the chemical will have been deleted, the protein not made, and that mutant is able to grow in the presence of myrigalone A,’ says Williams. This revealed the target as an enzyme – 1-aminocyclopropane-1-carboxylic acid oxidase (ACO) – crucial for synthesising ethylene in plants. In silico modelling predicted that MyA directly binds to the active site of the ACO enzmye.

MyA is around 100 times more potent than established ethylene biosynthesis inhibitors. Tapping an online database, Williams and colleagues discovered a compound that could bind in the same place but was 5000-fold more potent than a commonly used ethylene inhibitor, 2-aminoisobutyric acid.

The new ethylene inhibitor could trigger crop plants to close their stomata in drought situations, reducing water loss through their leaves and enhancing survival. ‘We are looking for industrial and research partners,’ Williams says, ‘to take the next steps and validate that these compounds work in the field.’

‘There is a desire to better control ethylene biosynthesis and responses to improve crop production and postharvest storage,’ notes Brad Binder, a plant biochemist at the University of Tennessee, Knoxville.

Binder imagines several possible uses for a potent ethylene inhibitor. ‘One might be to prolong cut flower life so that the petals don’t fall off as quickly,’ he says. ‘Another would be to reduce germination of weeds prior to planting.’

‘Much more research is needed to explore the applications,’ Binder adds, including exploring off-target effects and human health and environmental effects.