Solanoeclepin A Characterization of a rhizosphere communication molecule in tomato and potato

Solanoeclepin A (SolA) is a metabolite that was isolated from the root exudate of 700 potato plants some 30 years ago and was shown to be an active hatching factor for the plant root endoparasitic Potato Cyst Nematode (PCN). Since this initial discovery it has been mostly silent about SolA and nothing became known about its biosynthetic pathway or possible other roles of this molecule within the plant and/or the rhizosphere. In her thesis, Alessandra Guerrieri studies a number of approaches with the objective to shed more light on this elusive molecule. This starts with the development of a highly sensitive analytical method which allowed her to detect SolA in the root exudate of single plants. With this method she demonstrates the presence of SolA in the root exudate of a range of different Solanaceae species, including tomato and wild relatives, as well as a substantial number of wild potato species. In the latter she finds an indication for the existence of an alternative hatching factor, tentatively coined solanoeclepin B. To be able to investigate potential biosynthetic gene candidates she subsequently develops systemic Virus Induced Gene Silencing (VIGS). She shows that she can efficiently knock down the expression of genes in the roots of tomato using a TRV vector, and that she can change the root exudate composition with constructs targeting genes essential for root triterpenoid/steroid metabolism. Moreover, she shows that this results in changes in the microbiome. Finally, her analytical method also enabled her to investigate the effect of environmental conditions on SolA production and she demonstrates that nitrogen deficiency and the presence of a microbiome greatly increase the SolA concentration in the root exudate. This effect she subsequently uses in a large omics approach in which she combines transcriptomics, metabolomics and microbiome metabarcoding to come up with gene candidates for SolA biosynthesis.