Lay summary

ATP-binding cassette (ABC)proteins are ubiquitously found in prokaryotes and eukaryotes. Theycatalyze the primary active transport of a multitude of substrates, such asglutathionated compounds, alkaloids, terpenoids, lipids, heavy metals andpeptides. Recent progress on plant ABCtransporters demonstrates that they transport substrates, which have not beendescribed in other organisms such as auxins and abscisic acid (ABA), as well asthe main storage compound for phosphate, , phytate), which also acts as asignalling compound6phosphate (InsPkisinositol hexa.

In the present project wewill address two questions related to ABC transporters with the aim toelucidate the role of these transporters in plant hormone transport and signaling

transport. 6 compartmentationaffects hormone levels and how interacting partners modulate InsP6 transport affects auxin and/or ethylene levels.Based on these results we will investigate how InsP6transport affectsguard cell functioning. We identified interacting partners and got first indicationsthat impaired InsP6 transporter. Sofar it is unknown, how altered vacuolar InsP6 andauxin. Recently we showed that AtABCC5 is an InsP2+(A) Loss-of-functionmutants for AtABCC5 are impaired in their response to ABA, Ca

(B) In the second projectwe are interested to identify and characterize a strigolactone transporter. Strigolactonesare involved in two diverse processes, mycorrhization and shoot branching. Wefound that the Petunia Phpdr1 mutants are impaired in mycorrhization andexhibit increased shoot branching, indicating that this ABC transporter couldbe involved inĀ  export of strigolactone formstrigolactone-producing cells. In the frame of the present project we envisageto further characterize the transport activity, the localization and thefunction of PhPDR1 in mycorrhization and shoot branching.