<i>In vivo</i> interaction between <i>at</i>Toc33 and <i>at</i>Toc159 GTP-binding domains demonstrated in a plant split-ubiquitin system

The GTPases <i>at</i>Toc33 and <i>at</i>Toc159 are pre-protein receptor components of the translocon complex at the outer chloroplast membrane in <i>Arabidopsis</i>. Despite their participation in the same complex <i>in vivo</i>;, evidence for their interaction is still lacking. Here, a split-ubiquitin system is engineered for use in plants, and the <i>in vivo</i>; interaction of the Toc GTPases in <i>Arabidopsis</i> and tobacco protoplasts is shown. Using the same method, the self-interaction of the peroxisomal membrane protein <i>at</i>Pex11e is demonstrated. The finding suggests a more general suitability of the split-ubiquitin system as a plant <i>in vivo</i>; interaction assay.