Structure-function analysis reveals Trichoderma virens Tsp1 to be a novel fungal effector protein modulating plant...

Area of Science:

• Plant-fungal interactions
• Molecular biology
• Structural biology

Background:

• Trichoderma virens forms symbiotic relationships with plants, providing defense in exchange for nutrients.
• The Tsp1 protein from T. virens was identified as upregulated during maize root colonization.
• Tsp1 is conserved in Ascomycota fungi, but its function and structure were previously unknown.

Purpose of the Study:

• To elucidate the structure and function of the Tsp1 protein from Trichoderma virens.
• To investigate the role of Tsp1 in plant-fungal interactions and plant defense mechanisms.

Main Methods:

• Recombinant Tsp1 protein expression and purification.
• X-ray crystallography for structure determination (1.25 Å resolution) from two crystal forms using Se-SAD.
• DALI-based structural comparison with known fungal effector proteins.
• Plant defense assays and RT-qPCR analysis to assess Tsp1's effect on plant susceptibility.

Main Results:

• The crystal structure of Tsp1 revealed a beta-barrel fold, forming dimers in both crystalline and solution states.
• Structural analysis showed similarity to known fungal effectors Alt a1 and PevD1, suggesting Tsp1 belongs to a novel effector family.
• Tsp1 was found to induce salicylic acid-mediated susceptibility in maize plants.
• Maize plants treated with Tsp1 exhibited increased susceptibility to the necrotrophic pathogen Cochliobolus heterostrophus.

Conclusions:

• Tsp1 represents a novel family of fungal effector proteins with a conserved beta-barrel structure.
• Tsp1 plays a role in modulating plant defense pathways, specifically by inducing salicylic acid responses.
• This interaction enhances plant susceptibility to pathogens, highlighting a new mechanism in fungal pathogenesis.