Pathogenic Bacteria Target Plant Plasmodesmata to Colonize and Invade Surrounding Tissues.

Area of Science:

• Plant pathology
• Molecular plant-microbe interactions
• Cellular communication

Background:

• Multicellular organisms rely on intercellular communication for homeostasis.
• Plasmodesmata (PD) are crucial for plant cell-to-cell communication.
• Plants typically close PD during immune responses to pathogens.

Purpose of the Study:

• To investigate the role of the bacterial effector protein HopO1-1 in modulating plant plasmodesmata function.
• To understand how HopO1-1 contributes to the spread of *Pseudomonas syringae* infection in plants.

Main Methods:

• Investigated the effect of HopO1-1 expression on molecular flux through plasmodesmata in Arabidopsis.
• Assessed the requirement of HopO1-1 catalytic activity for PD modulation.
• Examined the physical interaction between HopO1-1 and PD-located proteins (PDLP7, PDLP5).

Main Results:

• HopO1-1 is essential for the local spread of *Pseudomonas syringae*.
• HopO1-1 expression enhances PD-dependent molecular flux between plant cells.
• HopO1-1's catalytic activity is necessary for PD regulation.
• HopO1-1 interacts with and destabilizes PDLP7 and potentially PDLP5, proteins involved in bacterial immunity.

Conclusions:

• Pathogenic bacteria can manipulate host intercellular communication via effector proteins.
• HopO1-1 facilitates bacterial infection by enhancing plasmodesmata function.
• Targeting PDLP proteins is a strategy used by pathogens to overcome plant defenses.