In case of threats plants cannot run away but they do have a defence comparable to the humane immune system. This plant immune system helps them to fight off for example microorganism attacks. By so-called defence priming the plant immune system can be trained to memorize threats and act more effective against them in future. Solid knowledge about this mechanism is still scattered. A group of UPSC researchers lead by Benedicte Albrectsen tried the first systematic approach and published a meta-analysis on defence priming in plants focusing on thale cress.
How the plant immune system memory works is not yet fully understood but it is known that different molecular mechanisms act. The whole process is triggered by external stimuli, so-called priming agents. Priming agents can be living organisms, like microorganism and arthropods or chemical compounds, like vitamins and plant hormones. These triggers can induce the priming process in all kind of plant tissues and developmental stages. During the so-called priming phase, the plant gets stimulated by a priming agent in absence of actual threats. It accumulates compounds that later play a role in the defence. The primed status is durable, does not decrease the plants fitness and can be even passed on to the next generation.
Defence priming is a known phenomenon but for applying it widely in agriculture further knowledge is needed. In the current study the researchers analysed more than 240 studies on thale cress (Arabidopsis thaliana). The group tried to find patterns in plant responses to stress and identify possible relationships between priming agents and antagonists, like pathogens or herbivores. With their analysis they clearly show that defence priming enables the plant to withstand subsequent danger better than un-primed conspecifics. It helps the plant to defend itself faster and more effective the next time the same stress occurs.
The elaborate data comparison also allowed the researchers to identify potential players in the priming challenge. “We present a list of potential priming agents that we suggest could improve plant resistance properties in the future”, explains Benedicte Albrectsen. “The list includes microorganisms and organic chemical compounds with varied effect”. They showed that several compounds, like fungi and vitamins act as strong priming agents in thale cress whereas the influence of herbivores on the priming effect seems rather week.
This publication supports the theory that defence priming has an effect. It emphasizes that on the long run it can be used to enhance thread-resilience also in crops. The current agricultural systems are facing severe challenges including increasing demands, higher costs, and a changing climate. Defence priming has the potential for raising crop productivity with little environmental risk and this could help to move towards a more sustainable agriculture.
The work was recently published in Scientific Reports:
Westman SM, Kloth KJ, Hanson J, Ohlsson AB & Albrectsen BR (2019). Defence priming in Arabidopsis – a Meta-Analysis. 9:133309 (doi.org/10.1038/s41598-019-49811-9)
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