Research area 2

Prolonged sulfate deficiency causes severe growth retardation and is of relevance for crop production. Partitioning of flux can take place at several branch points in sulfur metabolism and depends on the environmental challenge, e.g. nutrient limitation, high light or herbivore defense. We are interested in the organismal response to limitation of soil resources such as water and nutrients. Sulfur deficiency and water deficit share the acclimation response of growth arrest of the shoot while maintaining root growth to allow for foraging for new resources. We could show that this massive shift of biomass allocation from shoot to root is governed by the central sensor kinase complex Target of Rapamycin (TOR). Analysis of this fundamental eukaryotic sensor kinase in Arabidopsis under sulfate starvation conditions revealed of differential TOR complex activity in shoots and roots. Surprisingly, sulfur availability is not transmitted directly to TOR but by the so-called glucose-TOR axis. Lowered TOR complex activity goes along with enhanced autophagy in the shoot to generate sucrose for transport to the root. This helps to maintain TOR complex activity, suppress autophagy and activate the root apical meristem. These findings help to explain one of the fundamental acclamatory traits in plants to major soil resource deficiencies.