A fungal powdery mildew pathogen induces extensive local and marginal systemic changes in the Arabidopsis thaliana...

Area of Science:

• Plant pathology
• Microbiome research
• Plant-microbe interactions

Background:

• Powdery mildew is a significant foliar disease caused by ascomycete fungi.
• The impact of powdery mildew on host-associated microbial communities, both locally and systemically, is not well understood.

Purpose of the Study:

• To investigate how powdery mildew (Golovinomyces orontii) colonization affects resident microbial communities in Arabidopsis thaliana.
• To differentiate between local (foliar) and systemic (root) effects on fungal and bacterial communities.

Main Methods:

• Infection experiments using Arabidopsis thaliana in natural soil and gnotobiotic systems.
• Introduction of powdery mildew into plants with pre-established synthetic bacterial communities (SynComs) derived from leaf or root microbes.
• Analysis of fungal and bacterial community structure in both foliar and root tissues post-infection.

Main Results:

• Golovinomyces orontii outcompeted resident leaf fungi, but root fungal communities remained stable.
• Significant shifts were observed in foliar bacterial communities, while root bacterial communities showed minor changes.
• Pre-colonization with leaf-derived SynComs led to similar foliar bacterial shifts, whereas root-derived SynComs were resilient to foliar infection.
• Fungal infection doubled the leaf bacterial load, independent of the leaf SynCom's presence.

Conclusions:

• Powdery mildew infection predominantly influences microbial communities in the local plant tissue (leaves).
• Changes in source-sink relationships and host immune status are potential drivers of these microbial shifts.
• Root microbial communities exhibit resilience to foliar powdery mildew infection.