Trichoderma swollenin activates AtABCB5-dependent auxin efflux to promote plant development

Area of Science:

• Plant-microbe interactions
• Molecular plant pathology
• Fungal effector biology

Background:

• The beneficial fungus Trichoderma enhances plant growth and stress tolerance via unknown mechanisms.
• Understanding these mechanisms is crucial for developing effective agricultural applications.

Purpose of the Study:

• To elucidate the molecular mechanisms by which Trichoderma harzianum promotes plant growth.
• To identify the specific fungal components and plant targets involved in this interaction.

Main Methods:

• Investigated the role of Trichoderma harzianum swollenin (ThSWO) in root colonization and plant growth promotion.
• Utilized protein localization studies and biochemical assays to characterize ThSWO-plant interactions.
• Employed structure-guided mutagenesis to analyze the functional consequences of ThSWO binding to the AtABCB5 transporter.

Main Results:

• ThSWO facilitates root colonization and plant growth promotion.
• ThSWO interacts with the plant ABC transporter AtABCB5, enhancing its function as an auxin efflux carrier.
• ThSWO binding induces phosphorylation of AtABCB5, increasing indole-3-acetic acid (IAA) efflux and triggering downstream auxin responses.

Conclusions:

• A fungal effector (ThSWO) co-opts host auxin transport machinery to promote plant development.
• This interaction involves ThSWO binding to and modulating the activity of the AtABCB5 transporter.
• Findings provide a molecular basis for Trichoderma-mediated plant growth promotion with implications for crop improvement strategies.