Plant resistance to aphids to reduce virus epidemics

No antiviral molecules exist in agriculture, and until recently it was thought that plants had no immune system enabling them to fight viruses. This idea has changed recently with the discovery of genetic systems in plants that can be activated by aphids and be effective against viruses.

Since 2013, plant-aphid interactions have been integrated into the Triggered Immunity Model, a model developed since the 1990s for pathogen-plant interactions. This model describes the molecular dialogue between pathogens and plants, which is initiated in the intercellular space colonized by the pathogen and then inside the cells to which the pathogen inject 'effectors'. Recognition of these effectors by NLR (nucleotide binding/leucine rich repeat domains) proteins triggers plant defenses. This plant resistance system has been described in particular for viruses. Genes encoding NLR proteins conferring resistance to aphids have been formally identified in tomato (Mi), melon (Vat) and wheat (Adn).

Figure taken from Boissot 2023 (Current Opinion in Insect Science, 56, 1011008. hal-03972031v1)

Virus immunity triggered by aphids An effector introduced into a cell by aphid salivation is recognized by an NLR-type protein. This recognition triggers local cell death, blocking the replication and movement of viruses introduced at the same time as the effector. This recognition also triggers callose deposits in the apoplast, reducing access to the phloem and therefore the rate of virus transmission by sap-feeding insects

In field trials, the Vat gene was shown to effectively reduce epidemics of certain melon viruses, in particular those for which Aphis gossypii is the main vector.