This is a story about being lured to a death and how researchers take advantage of it:
The slender, brown moth with a checkered pattern on its back has a mission. She must find a good place to lay her eggs. This should not be that difficult. There are plenty of yellow flowering winter cress growing like weeds on the roadside. The plants lure the fertile diamondback moth to them with a special substance that stimulates her to lay her eggs in them.
But it is a death trap. The bait and the death trap are unique chemical properties of winter cress. These properties can be exploited in the fight against insect infestation in crops, whereby the use of pesticides can be reduced.
Researchers from Aarhus University and University of Copenhagen have taken a step in this direction. They have helped to map the genome of winter cress (Barbarea vulgaris) and found specific genes involved in the alluring and deadly substances.
– Knowledge of the genome of Barbarea vulgaris can lead to a better understanding of the mechanisms of ecological biochemistry beneficial for the breeding of crops with resistance, says Senior Scientist Torben Asp, Department of Molecular Biology and Genetics, Aarhus University.
Diamondback moth and agricultural crops
Back to the ill-fated moth. She lays her eggs on the underside of a winter cress leaf and flies away in good faith. Some time later, the larvae hatch. They gorge themselves on the leaf and thrive – for a little while. The poison from the plant builds up in the larvae, and eventually it becomes too much for them and they die. Life on the winter cress was a blind alley.
What happened was that the winter cress produces specific glucosinolates and saponins. Glucosinolates stimulate the spawning in the diamondback moth, while saponins are so toxic to the larvae that they die. But what does this have to do with agricultural crops?
Diamondback moths lay their eggs not only on winter cress, but the entire family of cruciferous plants, including important crops such as canola, mustard, and cabbage. Here insect larvae do great damage. The insects can be controlled with insecticides, but with time, they develop resistance against the insecticides. Therefore, there is a need to find other ways to combat the diamondback moth, and this is where the winter cress comes into the picture.
– Barbarea vulgaris is interesting because it is resistant to the diamondback moth due to its unique content of glucosinolates and saponins, says professor Søren Bak from the Department of Plant and Environmental Sciences, University of Copenhagen.
The smooth and the hairy
There are two subspecies of winter cress, though – a smooth (G) and a hairy (P). The two subspecies of B. vulgaris have different glucosinolate and saponine profiles. The smooth winter cress is the one that is resistant to diamondback moth and certain flea beetles. The plants contain the chemical substances glucobarbarine, cellobiosyl-oleanolic acid and cellobiosyl-hederagenin. The hairy type contains the chemical substance glucosibarin, and is not resistant to the diamondback moth and flea beetles.
The researchers have now sequenced the genome for the G-type and reviewed the mapping of the genome of the P-type. By comparing the two subspecies of B. vulgaris, they localised the genes that affect the glucosinolates and saponins.
– With a mapping of the B. vulgaris genome, we can gain a better understanding of the production of the specialised metabolites leading to disease and resistance to insects generally, and of the evolutionary events leading to the loss of resistance to a specific insect, as well as a changed glucosinolate profile in the biochemically innovative P-type, says Torben Asp, and continues:
– With glucosinolate and saponin profiles that are unique in the economically important family of the Brassicaceae plants, the Barbarea family is extremely interesting to use as a model for the studies of how plants and insects have evolved concurrently with each other in their arms race, and for research in the evolution of plant defences, and what drives it on the ecological, chemical and molecular level. The B. vulgaris genome gives us a valuable genomic resource for the production of rare or unique metabolites with ecological effects.
Source: Aarhus University