In a groundbreaking revelation, scientists have unveiled the intricate language of plants, demonstrating how they communicate via volatile organic compounds (VOCs) when faced with threats, a phenomenon first recognized in 1983. This profound discovery sheds light on how plants interpret VOCs as danger signals, prompting them to activate defensive measures. Utilizing innovative equipment and advanced imaging techniques, researchers have pinpointed the specific VOCs responsible and the plant cells that initiate the response. Their findings provide profound insights into the complex communication mechanisms of plants and their resilience in the face of potential harm.
Plant-to-Plant Communication Through Airborne Compounds
Plants emit volatile organic compounds (VOCs) into the atmosphere when subjected to mechanical damage or insect attacks. Unharmed neighboring plants detect these released VOCs as warning signals, triggering preemptive defense responses against imminent threats (Figure 1). This phenomenon of airborne communication among plants through VOCs was first documented in 1983 and has been observed in over 30 different plant species. However, the molecular mechanisms behind VOC perception and defense induction remain enigmatic.
Figure 1: Insects damaged plants release VOCs (dashed arrow), inducing Ca2+ signals (yellow arrowheads) in neighboring plants. Credit: Masatsugu Toyota/Saitama University
Pioneering Visualization of Plant Interactions
Led by Professor Masatsugu Toyota of Saitama University, Japan, the research team has achieved real-time visualization of plant-to-plant communication via VOCs, elucidating how plants assimilate VOCs, instigating calcium (Ca2+)-dependent defense responses against impending threats.
This groundbreaking research is set to be published in the prestigious journal Nature Communications on October 17, 2023. The study was spearheaded by Yuri Aratani, a Ph.D. student, and Takuya Uemura, a postdoctoral researcher, both working under Toyota’s guidance, in collaboration with Professor Kenji Matsui at Yamaguchi University, Japan.
“We designed specialized equipment to channel VOCs released by caterpillar-damaged plants onto intact neighboring plants, coupled with a real-time fluorescent imaging system in natural settings,” explains Toyota. This innovative setup visualized bursts of fluorescence within mustard plants (Arabidopsis thaliana) after exposure to VOCs emanating from insect-damaged plants (Figure 2; Video 1). These plants feature fluorescent protein sensors for intracellular Ca2+, enabling the observation of Ca2+ concentration changes through alterations in fluorescence.
“Intriguingly, aside from insect attacks, VOCs released from manually crushed leaves also induced Ca2+ signals in undamaged neighboring plants,” Toyota notes (Video 2).
Figure 2: Left panel: Equipment for exposing intact Arabidopsis to VOCs emitted by insect-damaged plants (dashed arrow). Right panel: Ca2+ signals (yellow arrowheads, 600 and 1200 s) were induced by VOCs released from insect-damaged plants (dashed arrow). Credit: Masatsugu Toyota/Saitama University
Identification of Crucial VOCs and Their Impact
To discern the specific VOCs responsible for inducing Ca2+ signals in plants, Toyota’s team conducted an investigation into various VOCs known to trigger defense responses in plants. Their research identified two key VOCs, (Z)-3-hexenal (Z-3-HAL) and (E)-2-hexenal (E-2-HAL), both six-carbon aldehydes, as inducers of Ca2+ signals in Arabidopsis (Figure 3; Video 3). These airborne chemicals, characterized by grassy odors, are known as green leaf volatiles (GLVs), emitted by mechanically damaged and herbivore-affected plants.
Video 3: Ca2+ signals were induced by VOCs released from insect-damaged plants. Credit: Masatsugu Toyota/Saitama University
Exposing Arabidopsis to Z-3-HAL and E-2-HAL led to the upregulation of genes associated with defense mechanisms. To elucidate the connection between Ca2+ signals and defense responses, researchers treated Arabidopsis with the Ca2+ channel inhibitor, LaCl3, and the Ca2+ chelating agent, EGTA. These chemicals suppressed both the Ca2+ signals and the activation of defense-related genes, providing compelling evidence that Arabidopsis perceives GLVs and activates defense responses in a Ca2+-dependent manner.
Figure 3: Airborne Z-3-HAL (orange broken line) induced Ca2+ signals (yellow arrowheads, 120 and 370 s) in Arabidopsis leaves. Credit: Masatsugu Toyota/Saitama University
Guard Cells: The Sentry of Plant Awareness
The researchers also pinpointed the specific cells responsible for exhibiting Ca2+ signals in response to GLVs. They accomplished this by engineering transgenic plants that exclusively expressed fluorescent protein sensors in guard, mesophyll, or epidermal cells. Following exposure to Z-3-HAL, Ca2+ signals emerged first in guard cells within approximately one minute, followed by mesophyll cells, while epidermal cells exhibited a slower response (Video 4). Guard cells, which are bean-shaped cells on plant surfaces, form stomata—small pores that connect inner tissues with the atmosphere.
Video 4: Airborne Z-3-HAL induced Ca2+ signals in guard (left video), mesophyll (central video), and epidermal cells (right video) in Arabidopsis leaves. Credit: Masatsugu Toyota/Saitama University
“Plants lack a ‘nose,’ but stomata serve as their gateway, facilitating rapid entry of GLVs into leaf tissues,” Toyota explains. Interestingly, the researchers found that pretreatment with abscisic acid (ABA), a phytohormone known for its role in stomatal closure, reduced Ca2+ responses in wild-type leaves. In contrast, mutants with impaired ABA-induced stomatal closures maintained normal Ca2+ signals in leaves even when exposed to ABA.
“We have, at last, unveiled the intricate narrative of when, where, and how plants respond to ‘warning messages’ from their imperiled neighbors,” Toyota asserts. “This ethereal communication network, concealed from our sight, plays a pivotal role in safeguarding neighboring plants from imminent threats with remarkable swiftness,” he adds.
This pioneering research not only deepens our appreciation for the extraordinary world of plants but also underscores nature’s remarkable endowment to ensure their survival and adaptability in the face of adversity. The profound implications of these findings transcend the realm of plant science, offering a glimpse into the intricate web of life on Earth.
Reference: “Green leaf volatile sensory calcium transduction in Arabidopsis” published on 17 October 2023, in Nature Communications.
DOI: 10.1038/s41467-023-41589-9
Funding: Japan Society for the Promotion of Science, Japan Science and Technology Agency, Shiraishi Foundation of Science Development
Table of Contents
Frequently Asked Questions (FAQs) about Plant Communication
What is the main discovery highlighted in this research?
The main discovery of this research is the revelation of how plants communicate with each other through volatile organic compounds (VOCs) when facing threats. It demonstrates that plants perceive these VOCs as danger signals, triggering defensive responses.
When was this phenomenon of plant communication via VOCs first identified?
This phenomenon of plant-to-plant communication through airborne compounds, specifically VOCs, was first documented in 1983.
What are volatile organic compounds (VOCs), and how do they work in plant communication?
Volatile organic compounds (VOCs) are chemical compounds emitted by plants when they undergo mechanical damage or are attacked by insects. Neighboring undamaged plants detect these VOCs as warning signals, which activate their defense mechanisms against potential threats.
Who led this groundbreaking research, and where was it conducted?
The research was led by Professor Masatsugu Toyota from Saitama University in Japan. It also involved collaboration with Professor Kenji Matsui at Yamaguchi University, Japan.
What is the significance of the identification of specific VOCs (Z-3-HAL and E-2-HAL) in this study?
The identification of specific VOCs, namely (Z)-3-hexenal (Z-3-HAL) and (E)-2-hexenal (E-2-HAL), is significant because these compounds were found to induce calcium (Ca2+) signals in plants, leading to the activation of defense-related genes. This demonstrates the mechanism by which plants respond to volatile compounds to protect themselves.
How do plants perceive VOCs, and what role do guard cells play in this process?
Plants perceive VOCs through their stomata, which are controlled by guard cells. When exposed to VOCs, guard cells rapidly respond, allowing these volatile compounds to enter the leaf tissues and trigger defense mechanisms.
What are the broader implications of this research?
This research not only deepens our understanding of plant communication but also highlights the remarkable ways in which nature equips plants to thrive and adapt in the face of adversity. The findings have implications beyond plant science, offering insights into the intricate interconnectedness of life on Earth.
When and where will the full research findings be published?
The full research findings will be published in the journal Nature Communications on October 17, 2023.
More about Plant Communication
- Nature Communications Journal
- Saitama University, Japan
- Yamaguchi University, Japan
- Japan Society for the Promotion of Science
- Japan Science and Technology Agency
- Shiraishi Foundation of Science Development
5 comments
wow, amazin’ stuff bout plants talkin thru vapors! cant belive they got pic-tures too.
cant w8 to c this in Nature Commuications journal!
interstin how stomata help in. nature so cool!
wat other secrets plants hide? im intrigued!
dis discovry wil help in plant studiez, gr8 job by Masatsugu Toyota!