When plants get under stress – be it due to heat, dryness or insect eating – they produce diverse chemical compounds for their protection. One of these compounds is the fleeting organic molecule isoprene. So far, however, his role was insufficiently understood. A study now shows that isoprene helps the plants to ward off predators. In addition, it boosts the production of the plant hormone jasmonic acid, which makes leaves for insects inedible. From the research of the researchers, the findings open up new opportunities for pest control.
Time damage to crops ensures year for year that between 20 and 40 percent of the harvests are lost. The economic losses are around $ 70 billion worldwide. The problem is exacerbated by global warming, because the higher temperatures accelerate the metabolism of the insects. Despite ecological and health concerns, more and more insecticides are therefore used. “In order to ensure global nutritional security, it is crucial to find or develop plants with increased pest resistance,” explains a team around Abira Sahu from the Michigan State University.
Natural protection strategy
In search of new approaches to crop protection, Sahu and their colleagues have taken a look at the natural defense strategies of the plants. “Many plants release a fleeting organic molecule called Isoprene, which increases the resistance to various environmental pollution,” reports the research team. It is already known that isoprene protects against abiotic stress factors such as heat, dryness and ozone. Trees such as oaks, poplars and spruces therefore release isoprene, especially at high temperatures. So far, however, it was unclear to what extent the substance also plays a role in biological pest defense.
In order to clarify this question, the researchers used tobacco plants that do not produce an isoprene, as well as modified tobacco plants, which are able to release this fleeting hydrocarbon connection thanks to a genetic addition. For their experiment, the researching caterpillars of the tobacco swarmer opened on both types of tobacco plants. In addition, they examined the extent to which the two plant groups were affected by white flies, another widespread type of plant pest.
Reduced insect feed
The result: “Tobacco swarm caterpillars, which were raised on isoprene-free tobacco plants, showed growth compared to their conspecifics on the control tobacco plants,” reports the team. If the caterpillars had the free choice between tobacco plants with and without isoprene, they preferred the plants without this fleeting substance. Although they also crawled over the plants with isoprene, they avoided eating their leaves. A similar result was shown in the white flying. “The number of white flies on the isoprene-free tobacco plants was significantly lower,” report Sahu and her colleagues.
In order to track down the underlying mechanisms, the researchers analyzed the genetic activity of tobacco plants under the influence of isoprene. They found that this hydrocarbon compound highly regulated the genes for natural defenses of the plants. The plants produced the plant hormone jasmonic acid under the influence of isoprene, which is known to deter insects. If the leaves were mechanically injured, both the release of isoprene and the production of jasmonic acid increased. Even in the event of non-stressed plants, the researchers were able to trigger this reaction by using the plants with isoprene.
Weighing between growth and defense
The researchers indicate that depending on the environmental conditions, it is important for the plants to find a suitable compromise between growth and defense. Because the production of defensive substances such as isoprene and jasmonic acid is energy -consuming and the more resources the plant uses, the less it can be in its growth. In fact, it was also evident in the experiment that the isoprene-free tobacco plants grew less than the non-modified tobacco plants. However, the stronger the threat from feed insects, the more this investment is worthwhile.
From the researcher’s point of view, the findings could help develop new strategies for crop protection. “If useful plants are enabled to produce isoprene by genetic modifications to defend themselves against pests, the dependence on chemical pesticides could be reduced,” writes the research team. “This could promote sustainable agriculture and secure economic stability to farmers.”
Source: Abira Sahu (Michigan State University, USA) et al., Science Advances, Doi: 10.1126/sciadv.adu4637