ARFA1 and its interacting protein FIP2 mediate bacterial infection and the formation of nitrogen fixing nodules in Medicago truncatula

EYLENSTEIN, ANDRES; BLANCO, FLAVIO A.; TRAUBENIK, SOLEDAD; RIVERO, CLAUDIO; ZANETTI, MARÍA EUGENIA

Modalidad Virtual

Congreso; Plant Biology 2020 Worldwide Summit; 2020

American Society of Plant Biology

Legume plants have the capacity to fix atmospheric nitrogen by establishing an endosymbiotic interaction with soil bacteria known as rhizobia, which results in the formation of nitrogen fixing nodules. Bacteria are internalized trough a tightly regulated process that requires membrane remodeling and vesicle trafficking leading to the formation of a tubular structure referred to as infection thread. The ARF family of monomeric GTPase mediates vesicle budding in a wide number of biological processes. Our studies have focused on the role of a member of the ARF family, ARFA1, during the root nodule symbiosis in Medicago truncatula. Overexpression of constitutively active or dominant negative mutant versions of ARFA1 affected root development and bacterial infection. Supporting the role of ARFA1 in bacterial infection, immunolocalization assays showed that ARFA1 localized around infection threads. A yeast two hybrid screening using ARFA1 as a bait identified FIP2, a protein with a BTB/POZ domain that acts as a substrate-specific adaptor of the Ubiquitin ligase E3 CUL3. The interaction occurs both in the cytoplasm and in punctuate structures, in an independent manner to the ARF1 GTP-association state. Using fluorescent cell markers, we found that this punctuate structures correspond to late endosome vesicles. FIP2 and ARFA1 showed a similar expression pattern in the different nodule zones. Overexpression of FIP2 resulted in an increased number of nodules, indicating a role of FIP2 in nodule organogenesis. All together, these results support a role for ARFA1 and FIP2 in the vesicle trafficking required for bacterial infection and the formation of nitrogen fixing nodules.