The microbe-free plant: fact or artifact?

Area of Science:

• Microbiology
• Plant Science
• Ecology

Background:

• Plants are consistently associated with diverse microbial communities, both above and below ground.
• These plant-associated microbes include mycorrhizal fungi, Rhizobia, bacteria, and endophytes, forming a critical part of the plant's biology.
• A microbe-free plant is an exception, not the rule, highlighting the ubiquity of plant-microbe interactions.

Purpose of the Study:

• To emphasize the importance of plant-microbe interactions in plant biology, ecology, and evolution.
• To challenge the conventional view of microbe-free plants as the 'normal' state in research.
• To advocate for new research approaches that consider the full spectrum of plant-microbe associations.

Main Methods:

• Reviewing the roles of various plant-associated microbes (endophytes, epiphytes, rhizosphere bacteria, etc.).
• Analyzing the direct and indirect mechanisms by which microbes affect plant parameters like nutrition, growth, and stress resistance.
• Proposing cultivation-independent screening methods (e.g., direct PCR) for assessing microbial diversity in wild plants.

Main Results:

• Plant-associated microbes significantly impact plant nutrition, growth, stress resistance, survival, and distribution.
• The outcome of plant-microbe interactions is context-dependent, varying with environmental conditions.
• Considering microbe-free plants as controls can hinder research on phenotypic plasticity, ecological outcomes, and plant evolution.

Conclusions:

• A paradigm shift is needed to view plants as holobionts, integrating microbial influences into fundamental research.
• Future research should utilize cultivation-independent methods to study microbial diversity in wild plants.
• Experimental studies should investigate host-endophyte interactions across diverse conditions and biological levels to understand the mutualism-parasitism continuum.