Deathly Scents

The perfume 1 - how to sooth killer algae

Plant immunity is composed of two layers - an evolutionary ancient basal immunity, and a specialised immunity. The specialised immunity is very efficient and resulted from a long evolutionary race of arms between pathogen and host plant. The current diseases of our cultivated grape that was domesticated in Europe were introduced only in the second half of the 19th century. In evolutionary terms, 150 years are too short to lead to a specialised immunity. We have therefore collected wild grapes from all over the world and searched for other forms of immunity against Downy Mildew. This pathogen is not really a fungus, but rather a parasitic alga that penetrates through the stomata and grows - untouched from any fungicides - inside the leaf. Searching for new targets we were successful: wild grapes from East Asia use a perfume - nonanal. This volatile compound normally is emitted from stomata and helps the zoospores of the pathogen to track the stomata for rapid penetration. When this "mouth odour" of grapevine is secreted all over the leaf surface, the misguided zoospores fail to infect the leaf (broadcast in the Deutschlandfunk on this topic). Also the Wild European Grape seems to employ this strategy.

The perfume 2 - how to drive cells into suicide

During her Ph.D. project Sahar Akaberi discovered that the enzyme hydroperoxylyase can activate programmed cell death. The product of this enzyme, the scent compound cis-Hexenal activates a suicide programme. The biological function of this kamikaze strategy has to be seen in the defence against pathogens that are specialised to turn the infected host cell into a Zombie. We work now together with Dr. Oliver Trapp, Julius-Kühn-Institute in Siebeldingen for a CRISPR-Cas strategy to know down this gene to test, how this will change the response to pathogens.