Methyl3-indolyacetate produced by a gut bacterium of the tephritid gall fly is implicated in controlling Crofton weed by reducing its lignin synthesis

Area of Science:

• Plant-insect interactions
• Microbial ecology
• Biocontrol agents

Background:

• Eupatorium adenophorum is an invasive plant causing ecological and economic damage.
• The interaction between E. adenophorum, its insect P. utilis, and the insect's gut microbiota is complex.
• Understanding these interactions can lead to novel biocontrol methods.

Purpose of the Study:

• To investigate the tripartite interaction between E. adenophorum, P. utilis, and P. utilis's enteric microbiota.
• To identify microbial compounds with herbicidal activity against E. adenophorum.
• To explore the potential of these compounds as bioherbicides.

Main Methods:

• Isolation and identification of gut-associated bacteria from P. utilis larvae.
• Bioactivity-guided characterization of phytotoxins.
• Assessment of herbicidal activity on E. adenophorum seed germination and plant development.
• Histological and transcriptomic analyses to elucidate the mechanism of action.
• Enzymatic assays to measure lignin content.

Main Results:

• Kluyvera ascorbata SZLYS-22 was isolated from P. utilis larvae, exhibiting herbicidal activity.
• Methyl indole-3-acetate (MeIAA) was identified as the primary phytotoxin, causing germination inhibition and morphological aberrations.
• MeIAA induced cytological disorganization in vascular tissues and down-regulated key genes in the phenylpropanoid pathway, reducing lignin.
• Transcriptomic data revealed compensatory C4H expression, insufficient to maintain lignification.

Conclusions:

• MeIAA is a novel bioherbicide that disrupts lignocellulosic integrity by modulating plant pathways.
• The study highlights the role of insect-associated microbiota in plant-insect interactions and biocontrol.
• Findings provide a basis for developing microbiome-informed biocontrol strategies against invasive E. adenophorum.