Arabidopsis phospholipase Dδ as an initiator of cytoskeleton-mediated signalling to fundamental cellular processes

Abstract

Phospholipase D (PLD), in combination with the cytoskeleton, plays a key role in plant signal transduction. One isotype of the multigene Arabidopsis PLD family, AtPLDδ, has been implicated in binding microtubules, although the molecular details of the mechanism and identities of potential interaction partners are unclear. We constructed a GFP-AtPLDδ reporter gene, stably transformed it into an Arabidopsis suspension cell line, and used epitope-tagged affinity pull-down assays to isolate a complex of co-purifying proteins. Mass spectrometry analysis of the complex revealed a set of proteins including β-tubulin, actin 7, HSP70, clathrin heavy chain, ATP synthase subunits, and a band 7–4/flotillin homologue. Sequence alignments with defined tubulin- and actin-binding regions from human HsPLD2 revealed highly homologous regions in all 12 AtPLD isotypes, suggesting direct interactions of AtPLDδ with tubulin and actin, while interactions with the remaining partners are likely to be mediated by the cytoskeleton. We propose that AtPLDδ acts through a complex of cytoskeletal and partner proteins to modulate fundamental cellular processes such as cytoskeletal rearrangements, vesicular trafficking, assembly of Golgi apparatus, mitosis and cytokinesis.