A novel CUL3 substrate-adaptor is physically associated to the small GTPase ARFA1

RIVERO, CLAUDIO; ZANETTI, MARÍA EUGENIA; BLANCO, FLAVIO

Cordoba

Congreso; XXXII Reunión Argentina XVI Congreso Latinoamericano de Fisiología Vegetal; 2018

We have previously shown that the monomeric GTPase ARFA1 is involved in vesicular trafficking processes associated with root growth and the symbiosis between legumes and nitrogen-fixing bacteria. A yeast two-hybrid screening using ARFA1 as bait identified 15 positive clones. Five of them correspond to FIP2, a protein with a BTB/POZ domain that forms a complex with the Ubiquitin ligase E3 CUL3 acting as a substrate-specific adaptor. Bimolecular fluorescence complementation assays in Nicotiana benthamiana leaves confirmed the interaction and revealed that occurs mainly in the plasma membrane. FIP2 was able to interact with both a constitutive active and a dominant negative version of ARFA1, suggesting that GTP activation of ARFA1 is not required for the interaction. FIP2 is ubiquitously expressed in different tissues, including different nodule zones, showing an expression pattern similar to ARF1. ARFA1 and FIP2 mRNA levels or their association to the translational machinery are not modified during the symbiotic interaction. Currently, we are conducting a reverse genetic approach in Medicago truncatula plants to elucidate the role of FIP2 in nodule symbiosis.