Role of the PP2 phloem protein in interorgan communication and long distance trafficking of proteins

Abstract: Phloem proteins 2 (PP2) are one of the most abundant proteins in the phloem sap. PP2s present a characteristic lectin activity, binding to proteins and RNAs and are transported from cell-to cell. Moreover, PP2 are associated to the specific P-proteins present in the sieve elements. The physiological function of these proteins is however poorly understood. Their lectin activity as well as their protein- and RNA-binding properties are though to undergo chaperon effects over long distances on macromolecules trafficking. Also PP2 have been proposed to act, together with the P-proteins, on the regulation of phloem sap stream. We previously characterized the PP2 family in Arabidopsis based on amino acid sequence similarities. The main member of this family, PP2-A1, is specifically expressed in the phloem companion cell-sieve element complexes. Deregulation of PP2-A1 gene led to alterations of development, architecture and growth. This is thought to reflect either a defect in long distance trafficking of signal molecules, or an alteration of general phloem sap flow. The objectives of the PhD project are to further describe the contribution of PP2s to long distance translocation and signalling through the phloem.

PhD subject IJPB 2011 from research group Phloem, transport and signalisation