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Poster

Session: Session 1 Presenting Authors at Posters (Odds)

P-347 - An effector that HIPP-hops? Functional and structural characterisation of a novel fungal effector-host target complex at plasmodesmata

Monday, July 14, 2025
13:30 - 15:15  
Location: Confex Hall 3
Subcellular dynamics and signaling in host-microbe interactions

Across diverse pathosystems, host proteins with heavy metal-associated (HMA) domains have been repeatedly identified as binding partners of pathogen effectors, as well as determinants of infection success. However, the endogenous functions of these HMA proteins, especially in the context of plant defence, are not well understood. As a novel case study, we discovered an effector named ChEC108 from the anthracnose fungus Colletotrichum higginsianum, which targets a tandem HMA domain-containing protein from Arabidopsis thaliana, HIPP6. In Arabidopsis leaves, ChEC108 and HIPP6 exhibit striking plasmodesmal localisation, and ChEC108 exploits these membrane-lined channels to move between plant cells. X-ray crystallographic structures revealed that ChEC108 is capable of binding either of the HIPP6 HMA domains via a near-identical mechanism, involving co-ordination of a metal ion at the binding interface. Metal binding residues of the HIPP6 HMA domains are critical for both plasmodesmal localisation and ChEC108 binding, but ChEC108 targets plasmodesmata and moves cell-to-cell even in the absence of HIPP6. Although numerous HMA proteins have been previously implicated as susceptibility factors, our data suggest that, akin to an immune receptor, HIPP6 may positively regulate defence signalling upon ChEC108 binding. Together, these findings have uncovered potential new roles for HMA proteins in plasmodesmata-localised signalling during fungal infection.