A Systematic Look at the Mechanism of RNA Transport

Project leader: PD Dr. Manfred Heinlein

Project Team members: Dr. Annette Niehl

CNRS project website: http://www.ibmp.cnrs.fr/

Plants have a difficult life: Unlike animals and humans, they cannot run away for shelter. In order to survive under the challenge of various biotic and abiotic environmental, plants have evolved the ability to mount specific defense reactions. Interestingly, these reactions may not be restricted to exposed cells but also may occur in distant, non-exposed cells. Moreover, these systemic reactions may involve the systemic degradation of specific RNA molecules (systemic RNA silencing), indicating the ability of plants to exchange sequence-specific information between cells.

In fact, plant cells exchange informational RNA macromolecules through cytoplasmic bridges in the cell wall known as plasmodesmata. Together with the phloem sieve elements in the vascular veins and stems, the system of these highly regulated cell wall channels forms the structural basis for a symplastic communication network by which plants coordinate their cellular activities at a level above that of an individual cell.

In order to get insight into the molecular mechanism of RNA transport, our group investigates the cellular mechanism by which Tobacco mosaic virus (TMV) targets its RNA genome (vRNA) from sites of replication to plasmodesmata to achieve intercellular spread. Movement of vRNA is thought to occur in the form of a ribonucleoprotein (vRNP) complex and depends on a virus-encoded movement protein (MP) that serves as our convenient probe to isolate and characterize components of the intercellular RNA transport pathway.

We believe that the results of our studies will provide important insights into the mechanisms of intercellular communication in plants and the ways by which viruses hijack these mechanisms. Our findings are likely to have broad implications for our understanding beyond plants.

The pivotal role of RNA transport in animal systems and humans, for example, in the establishment of systemic RNA interference (C.elegans), during development (e.g. studies in Drosophila, Xenopus) or in the mediation of synapse-specific plasticity to neurons (e.g. in Aplysia), is well documented. By using the advantage of plants as a genetic system and also as a system amenable for studying RNA transport at the systemic level, we aim at providing information of general importance with regard to the establishment of cell polarity, RNA-mediated signaling, cell differentiation, and cell behaviour.