Skip to main content
ISMPMI Congress 2025 Main banner
Icon Legend
This session is not in your schedule.
This session is in your schedule. Click again to remove it.

Poster

Session: Session 2 Presenting Authors at Posters (Evens)

P-414 - Humidity-triggered ABA depletion shapes plant-bacteria competition for leaf water

Thursday, July 17, 2025
13:30 - 15:15  
Location: Confex Hall 3
Plant Regulation of biotic and abiotic stress – trade-offs

The bacterial phytopathogen Pseudomonas syringae pv. tomato (Pst) DC3000 induces water-soaked lesions in the leaf apoplast under high humidity, facilitating infection. However, how plants regulate their resistance to bacterial infection in response to humidity remains largely unclear. Here, we demonstrate that abscisic acid (ABA)-catabolizing enzyme ABA 8’-hydroxylase, encoded by CYP707A3, plays a critical role in this resistance in Arabidopsis thaliana. Elevated humidity induces CYP707A3 expression, which is crucial for reducing ABA levels and promoting stomatal opening, thereby limiting bacterial water-soaking and infection following leaf invasion. High humidity also increases cytosolic Ca2+ levels through the Ca2+ channels CNGC2 and CNGC4, with partial involvement of CNGC9, leading to the activation of the calmodulin-binding transcription activator CAMTA3, which drives CYP707A3 induction. However, Pst DC3000 counteracts this defense response through type III secretion effectors, such as AvrPtoB, facilitating water-soaking. These findings provide insights into the mechanisms underlying the competition between plants and bacteria for leaf water under elevated humidity.