Plant scientists develop light-based messaging tool to talk to plants

Picture a world where humans have the ability to converse with plants, forewarning them of impending pest invasions or extreme weather conditions. At the Sainsbury Laboratory, Cambridge University (SLCU), a team of plant scientists is striving to transform this science fiction into reality by employing light-based communication to establish a connection with plants.

While their groundbreaking optogenetics tool is in its infancy, Alexander Jones’ research group has already demonstrated its prowess in manipulating plant immunity and pigment production solely by modifying light.

Light, the universal medium of human daily communication, finds a new purpose in the hands of the Jones team. They are harnessing light to develop tools that facilitate communication between plants and humans, opening up the possibility of bi-directional interaction.

Previously, the University of Cambridge team engineered a set of biosensors (ABACUS2 and GPS1) that utilize fluorescent light to visually convey real-time insights into cellular processes within plants, unveiling the inner workings of critical plant hormones. These biosensors allow us to decipher how plants respond to environmental pressures—effectively, plants communicating with humans.

Their latest breakthrough, detailed in a publication in PLOS Biology, introduces a novel tool known as “Highlighter.” This tool leverages specific light conditions to activate the expression of target genes in plants, triggering responses such as defense mechanisms—an instance of humans communicating with plants.

The concept of humans engaging in meaningful communication with plants has long fired the imagination of many. If such a capability were achievable, it could bring about a revolution in agriculture and redefine our connection with the plant world.

Dr. Jones envisions the potential: “If we could alert plants to impending disease outbreaks or pest incursions, plants could mobilize their natural defense mechanisms, mitigating widespread damage. Additionally, we could notify plants of approaching extreme weather events, such as heatwaves or droughts, enabling them to adapt their growth patterns or conserve water. This could pave the way for more efficient and sustainable farming practices, reducing the reliance on chemical interventions.”

Optogenetics in plants

Exploring the intricacies of cellular activity demands precise control over biomolecular processes at the cellular level. Enter optogenetics, a scientific technique wielding light as the catalyst to either activate or deactivate specific cellular processes.

The method involves implanting light-sensitive proteins, known as photoreceptors, into the target cells. Subsequently, by illuminating these cells with light, scientists can trigger or halt the desired process.

Over the past decade, optogenetics has ushered in a revolution in neuroscience. By permitting biologists to dissect the functions of individual neurons, it has paved the way for groundbreaking revelations about the brain. This newfound knowledge has greatly advanced our comprehension of conditions like epilepsy, spinal injuries, and Parkinson’s disease.

Yet, applying optogenetics to plants has posed distinct challenges. Plants are already brimming with photoreceptors, utilizing a broad spectrum of light to orchestrate their growth and development. The transition from darkness to light in itself activates native plant photoreceptors and an array of cellular systems.

Complicating matters further, many highly effective optogenetic actuators incorporate genetic components from plants. This intricacy introduces the risk of cross-talk and interference with existing plant photoreceptors if deployed within the plant kingdom.

Highlighter can also bring light to biomolecular processes in plants

Bo Larsen, the mastermind behind the creation of Highlighter during his tenure at SLCU, has propelled us significantly closer to the aspiration of communicating with plants. He accomplished this by engineering an optogenetics system, initially rooted in prokaryotic organisms, into a eukaryotic system finely tailored for plant applications.

In the context of plants, Highlighter stands out for its ability to respond to minimally invasive light signals. It can be activated or deactivated with precision and remains impervious to the cyclical shifts between light and dark within growth chambers.

The present iteration of Highlighter remains dormant in the presence of blue light but springs to life in darkness and under white, green, and intriguingly, red light conditions. The team intends to continue refining Highlighter, although they have already showcased its prowess in exercising optogenetic control over plant immunity, pigment production, and a yellow fluorescent protein, all at the cellular level.

Dr. Jones emphasizes the significance of Highlighter, stating, “Highlighter represents a major stride in advancing optogenetic tools tailored for plants. Its high-resolution gene control has the potential to unlock answers to a wide array of fundamental questions in plant biology.”

He envisions a burgeoning toolkit with a diverse range of optical properties for plants, which could usher in exciting prospects for enhancing crops. For instance, envision a future where one light condition triggers an immune response, while another precisely times a specific trait like flowering or ripening—a vision poised to reshape agriculture.

The story behind the research

In pursuit of an optogenetic gene expression switch compatible with typical horticultural lighting conditions, Dr. Jones sought guidance from J. Clark Lagarias, a recognized authority in phytochrome and cyanobacteriochrome light-switches at UC Davis.

Lagarias proposed repurposing the prokaryotic CcaS-CcaR optogenetic system, initially derived from photosynthetic microbes, which relies on the balance of green (on) and red (off) light signals. By selectively altering the spectrum of white light essential for plant growth, it became possible to activate or deactivate genes with minimal disruption.

However, during the transformation of Highlighter into a eukaryotic optogenetic system, Dr. Larsen uncovered an unexpected response to blue light—essentially turning off the system. The question arose: Could this transformation have modified the green-red spectral properties of the CcaS photoreceptor?

Collaborating with Alex Jones, Ines Camacho, and Richard Clarke from the National Physical Laboratory (NPL), they delved into the matter. They confirmed that the new system retained its ability to utilize green and red light, akin to the original system. Yet, NPL’s spectroscopic analysis unveiled evidence of an additional, independent blue-light sensing capability.

Co-author Roberto Hofmann made a notable observation: Apart from the red-green sensing domain, CcaS possessed a secondary domain bearing resemblance to blue-light photosensors known as phototropins. It appeared that Highlighter had unveiled an inherent blue-sensing function within CcaS, presenting an alternative avenue for controlling CcaS-CcaR activity.

Source: University of Cambridge

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