Stress-Driven Transposable Element De-repression Dynamics and Virulence Evolution in a Fungal Pathogen.

Area of Science:

• Genomics
• Molecular Biology
• Plant Pathology

Background:

• Transposable elements (TEs) drive genome evolution and influence host gene expression.
• Stress conditions, like pathogen infection, can induce TE activity, but regulatory mechanisms remain unclear.
• Plant pathogens offer models to study stress-induced TE de-repression and its role in virulence.

Purpose of the Study:

• To investigate TE de-repression dynamics in Zymoseptoria tritici under different stress conditions.
• To understand the contribution of TE expression to pathogen virulence.
• To explore the influence of genomic context and genetic background on TE activity.

Main Methods:

• Analysis of TE expression landscape in four Zymoseptoria tritici strains.
• Experimental exposure to nutrient starvation and host infection stress.
• Examination of the Avr3D1 effector locus and nearby TE insertions.

Main Results:

• Nutrient starvation and host infection induced distinct sets of TEs, contrary to expectations.
• Miniature inverted-repeat TEs and long terminal repeat-Gypsy elements showed condition-specific de-repression.
• Genomic context and strain-specific genetic background were key predictors of TE de-repression.
• Proximity to TEs affected host gene expression, and genomic defenses against TEs were often ineffective.
• TE insertions near the Avr3D1 effector locus likely reduced its expression and virulence.

Conclusions:

• TE responsiveness to stress exhibits significant intraspecific variation in Zymoseptoria tritici.
• This variation in TE control across genetic backgrounds and locations has direct consequences for pathogen virulence.
• Understanding TE dynamics is crucial for dissecting pathogen evolution and host-pathogen interactions.