Session: Session 2 Presenting Authors at Posters (Evens)
P-434 - Exocyst complex EXO70 subunits and MLO proteins are molecular determinants of polarized secretion in trichomes and during powdery mildew attack
Thursday, July 17, 2025
13:30 - 15:15 Â
Location: Confex Hall 3
Spatial & temporal resolution of the interaction interface
University Professor RWTH Aachen University Aachen, Nordrhein-Westfalen, Germany
The advantage of cellular specialization over generalist functions spurred the development of multicellularity. This evolutionary leap did not occur once but at least three times independently in the ancestors of animals, fungi, and plants. Central to this specialization is cell differentiation, which relies on establishing cell polarity. Cell polarity is maintained through polarized secretion—the asymmetric distribution of cellular components. In plants, the molecular basis for polarized secretion is largely enigmatic. We recently identified members of the conserved EXO70 and MLO protein families as key molecular determinants of polarized secretion. For example, Arabidopsis thaliana trichomes deprived of the relevant EXO70 and MLO isoforms show the same defects in polarized callose deposition and develop intriguingly similar cell wall fingerprints during FTIR spectroscopy. Moreover, combined mutants lacking these isoforms exhibit a synergistically reduced susceptibility to powdery mildew penetration. Building on these observations, we mapped the clade-specific interaction network of EXO70 and MLO proteins using luciferase complementation and yeast two-hybrid assays and determined the distinct localization of fluorophore-labeled isoforms. Our findings suggest isform-specific roles for EXO70 and MLO proteins in polarized secretion. We will further exploit this data to trace the evolutionary trajectory of EXO70 and MLO divergence by sequence-structure-function analyses.
