Plant no-contact communication: Synchronizing soil microbiota with the neighbor
The production of volatile substances caused by biotic and abiotic stimuli of plants is known to affect surrounding plants. Volatile compounds in plants act as signals that transmit their own information to surrounding plants.
Plants live in one place from the moment they germinate to the day they die. So, are plants aware of their surroundings? In recent years, research has been actively conducted to show that plants survive by interacting with microorganisms in the surrounding environment including the soil. So, do plants communicate with other plants? One answer to that is the observation that biotic and abiotic stimulation of plants results in the production of volatile substances that affect neighboring plants. Volatile compounds produced by one plant act as signals to transmit information to neighboring plants and reconstructing their rhizosphere microbiota.
Accumulating evidence from numerous studies has revealed that the rhizosphere microbial community changes in response to changes in the host plant's immunity. Nevertheless, little is known about how microbial communities directly help plants emit volatiles.
During my career, I have mainly been engaged in studying microbial ecology and communities of plant rhizosphere as a postdoctoral researcher under the guidance of Dr. Choong-Min Ryu, who was the first person to reveal the role played by bacterial volatile compounds (BVCs) in plant growth and immunity. This provided me with a new perspective on the volatiles that mediates interactions between plants, which can be classified into two groups, BVCs and microbe-induced plant volatiles (MIPVs).
Initially, we wanted to find the answer to a simple question: Will a change in the rhizosphere microbial community initiated by the treatment of a single plant with a growth-promoting bacterium (PGPR) change the rhizosphere microbial community of neighboring plants through the emission of plant volatile signals? To answer this, we build novel experimental equipment in collaboration with Dr. GC Song (a co-author in these studies) that allows spatial separation between two plant groups using plastic acrylic boxes. Dr. GC Song and I were long-time friends, and we had great fun while designing the equipment and working on this project together.
We sequenced the genomes of rhizosphere microbial communities of spatially isolated tomato plants to determine whether there were any differences between the rhizosphere microbiota community of PGPR-treated plants and those of untreated plants. Surprisingly, we found that the rhizosphere microbiota of the spatially separated plants was synchronized. Our results suggested that the microbial communities of plant rhizospheres can transmit information not only through signal transmission between organs in the emitter plant but also to neighboring plants through air-borne volatiles.
This meant that microbial information can be communicated from one plant to another without them having to be in close contact, in much the same way as animals communicate over large distances via odors. By manipulating this volatile-mediated dialogue between plants, it should be possible to develop new forms of biological control in agriculture. For example, by virtue of this type of manipulation, a beneficial microbiome could be spread throughout an area of farmland by simply inoculating one plant with a locally beneficial microbe.
How this works between different plant species in nature is unknown. However, if plant volatiles also transmits microbial community information between different plant species, this could lay the foundation for further research into understanding how rhizosphere microbial communities form and interact with plants.
This research was incredibly rewarding not only because it led to the development of completely new types of plant incubators tailored to volatiles and rhizosphere microbes, but also because it threw light on a previously unsuspected form of inter-plant communication. From another perspective, it also helped me to broaden my links within the plant science community and develop interdisciplinary skills such as bioinformatics and instrument analysis.