Defense compounds on the move

According to the optimal defense theory, plants accumulate defense compounds to the highest level in those tissues with the highest fitness value while other tissues are often the site of production. Thus, we know that defense compounds are mobile. Moreover, due to their high metabolic cost plants appear to reuse defense compounds by remobilizing and transporting them to new storage tissues. An important prerequisite for studying mobility of a given metabolite is to know both where the metabolite is de novo biosynthesized and where it is stored at the cellular and subcellular level.  

What are the genes and processes involved in transport of defense compounds? How are they controlled to deliver the right amount of defense compounds to the correct location at the correct time during plant development? We address these questions using the glucosinolate defense compounds,in the model plant Arabidopsis. We know that glucosinolates first accumulate in green leaves and roots, then in reproductive organs such as flowers and lastly in seeds. In addition, Arabidopsis root exudes glucosinolates to the rhizosphere. Thus, we know that glucosinolates are very mobile.

Towards our goal of understanding glucosinolate mobility from source to sink our first aim is to identify the specific cell types involved. Evidence suggests that glucosinolates are produced in specific cell types embedded in the vasculature and stored in laticifer-like S-cells along the vasculature and the leaf margin. Currently, we are identifying glucosinolate-producing cells in Arabidopsis plants using transgenic lines with fluorophore-tagged biosynthetic enzymes and characterizing these cells with correlative transmission electron microscopy.

At the subcellular level, we are investigating how the glucosinolates are translocated from the ER-associated production site to storage in the S-cells. Does short distance glucosinolate transport from cell to cell include transporter proteins or plasmodesmata?

Ultimately, we want to unravel the mechanism behind S-cell accumulation, root exudation and seed loading using single cell metabolite analyses, TEM, grafting and bioimaging approaches, single seed analyses from segregating populations, and root exudation assays.



Contact persons

Barbara Ann Halkier
+45 353-33342

Associate Professor
Hussam H. Nour-Eldin
+45 353-698
Alexander Schulz
+45 353-33350
Deyang Xu

Assist. professor
Deyang Xu
+45 353-33555