DynaMo Mini Symposium on plant transport biology

We are pleased to invite to a DynaMo mini Symposium on plant transport biology with

Alain Gojon, Integrative Biology Institute for Plants, Montpellier, France &
John M. Ward, University of Minnesota, USA.

Alain Gojon:

Transceptor-mediated nitrate signaling in Arabidopsis
Nitrate is both a nutrient and a signal molecule in plants. Increasing evidence indicates that part of the nitrate sensing by the plant is ensured by plasma membrane nitrate carriers that fulfill a dual transport/signaling function, thus defining a new class of proteins called transceptors. I will present data suggesting that the CHL1/NRT1.1/NPF6.3 transporter plays a pivotal role in governing several physiological and developmental responses to nitrate in Arabidopsis thaliana. In particular, CHL1/NRT1.1/NPF6.3 regulates lateral root development by transforming changes in external nitrate concentration into changes in auxin gradients in lateral root primordia, due to its unique capacity to perform nitrate-regulated auxin transport facilitation. Furthermore, point mutations in CHL1/NRT1.1/NPF6.3 show that this protein triggers different responses to nitrate through separate mechanisms, and that different forms of the protein (e.g., phosphorylated or not) have distinct signaling roles.

John M. Ward:

Investigating substrate specificity of plant sucrose transporters (SUTs) and amino acid transporters (AAPs)
In plants, sucrose transporters (SUTs) and amino acid transporters (AAPs) are encoded by small gene families. In my lab we are focused on studying the structural basis for differences in substrate specificity between transporters within these families. We found that type II SUTs are more selective for sucrose compared to type I SUTs. We found that type I SUTs will transport coumarin glucosides, such as esculin, which are highly fluorescent, and this is useful for high-throughput transport assays. We used esculin uptake as a screen to select yeast expressing mutated SUTs and identified four amino acid positions important for substrate specificity in SUTs. Esculin is also a useful probe to study phloem loading in plants. Our work on substrate specificity of AAPs is at an early stage. We noticed that the ability to transport basic amino acids was lost at two different times during the evolution of AAPs and we are investigating the structural basis for this.

Everybody is velcome!