T6SS in plant pathogens: unique mechanisms in complex hosts.

Area of Science:

• Microbiology
• Bacterial Pathogenesis
• Plant-Microbe Interactions

Background:

• Type VI secretion systems (T6SSs) are bacterial macromolecular machines for effector delivery.
• Initially studied in human pathogens, T6SSs are now recognized for interbacterial competition, including in plant environments.
• Genes for T6SSs are prevalent in Gram-negative bacteria, particularly Proteobacteria, which include major plant pathogens.

Purpose of the Study:

• To review the known functions of T6SSs in phytopathogens.
• To discuss T6SS deployment against plant hosts and other organisms.
• To identify knowledge gaps regarding T6SS effector activity against plant cells.

Main Methods:

• Literature review of T6SSs in phytopathogens.
• Analysis of T6SS gene distribution in plant-associated bacteria.
• Synthesis of current understanding of T6SS effector functions.

Main Results:

• T6SSs are widely distributed in phytopathogenic bacteria, often encoded by multiple gene clusters.
• Phytopathogenic bacteria utilize T6SSs for interbacterial competition and colonization.
• Specific T6SS effectors like phospholipases and peptidases have characterized targets in non-plant interactions.

Conclusions:

• T6SSs are versatile tools for bacterial pathogens, including those affecting plants.
• Plant pathogens employ T6SSs for diverse roles during infection.
• Further research is crucial to elucidate the specific mechanisms and targets of T6SS effectors against plant cells.