In the quest for more sustainable and efficient production of valuable plant-derived compounds, scientists have long sought innovative methods to bypass the limitations inherent in traditional agriculture and plant harvesting. Extracting pharmaceuticals, cosmetics ingredients, or food additives directly from whole plants is often hindered by slow growth rates, seasonal variability, and environmental instability. As a result, plant cell cultures have emerged as promising biofactories capable of rapid multiplication under controlled laboratory conditions, unhindered by external climatic fluctuations. Despite their promise, these cultured cells typically express only a fraction of their extensive genetic repertoire, leaving a treasure trove of untapped metabolic potential dormant under conventional culture conditions.
Unlocking these hidden metabolic pathways has proved an enduring challenge in plant biotechnology. A groundbreaking approach gaining traction involves the use of microbial co-cultures, where the symbiotic or competitive interactions between different organisms spur the biosynthesis of novel compounds not produced when cultured individually. This strategy has yielded remarkable success in microbial systems, particularly among bacteria and fungi, revolutionizing natural product discovery and biosynthesis. However, applying co-culture strategies to plant cells has faced significant hurdles, primarily because most bacterial species either inhibit growth or outright kill plant cell cultures, thereby limiting the repertoire of microbial partners that could safely stimulate plant metabolism.
The intriguing concept of leveraging endophytic bacteria—microorganisms living benignly within plant tissues—has recently been explored by a research team at Tokyo University of Science, Japan. Led by Professor Toshiki Furuya, this group focused on isolating these natural symbionts from Japanese mustard spinach (komatsuna) and Japanese radish (daikon), assessing their ability to coexist with cultured plant cells and activate novel metabolic processes. Unlike pathogenic or opportunistic bacteria, these endophytes possess an inherent compatibility that enables them to thrive inside plants without eliciting adverse effects, making them ideal candidates for co-culture experimentation with plant cell lines.
The research primarily utilized tobacco BY-2 cells, a ubiquitous model system in plant biology due to their fast growth and ease of genetic manipulation. Introducing the endophytic bacterium Delftia sp. BR1R-2 into these cultures revealed stunning results. Unlike common bacterial strains such as Escherichia coli that rapidly compromise plant cell viability, BR1R-2 flourished alongside the plant cells without causing damage. This coexistence hinted at a potentially symbiotic mechanism that might trigger the activation of silent metabolic genes within the plant cells.
Chemical analyses using high-performance liquid chromatography (HPLC) substantiated these interactions at the molecular level. The co-culture induced marked increases in acetophenone derivatives—small molecules recognized for their antimicrobial and pesticidal properties. Simultaneously, levels of N-caffeoylputrescine, a common phenolic amide abundant in tobacco cells, decreased, indicating a reallocation of metabolic resources toward producing new bioactive substances. Extracts from the co-cultured cells exhibited inhibitory effects against plant pathogens, confirming the functional potency of these novel metabolites in plant defense.
Further investigation employing gene expression profiling illuminated the underlying biological pathways modulated by the interaction. The presence of the endophytic bacteria elicited upregulation of multiple defense-related genetic networks regulated by plant hormones central to immune responses, such as salicylic acid and jasmonic acid pathways. Notably, the activation was contingent on physical contact between the bacterial cells and the plant cells, underscoring the importance of intimate cell-to-cell communication in triggering metabolic shifts.
Crucially, the phenomenon was not isolated to this single bacterial strain or plant model. Parallel experiments with Pseudomonas sp. RS1P-1, an endophyte derived from radish, generated comparable metabolic alterations when co-cultured with both tobacco and Arabidopsis plant cells. This cross-species consistency suggests that endophyte-mediated activation of plant metabolic pathways is a broadly applicable strategy, potentially extendable to a variety of economically significant plants.
Professor Furuya emphasizes the transformative implications of these findings: by harnessing plant immunity-activating endophytic bacteria, researchers can safely unlock a vast array of metabolic pathways previously inaccessible in cultured plant cells. This capability opens exciting avenues for the scalable production of diverse phytochemicals, circumventing the inefficiencies of whole-plant cultivation and enabling tailored synthesis of high-value compounds with pharmaceutical, cosmetic, and agricultural applications.
Moreover, this approach dovetails elegantly with green chemistry principles, offering an environmentally responsible approach to biosynthesis that reduces reliance on harsh chemical synthesis or unsustainable agricultural practices. The interplay between endophytic bacteria and plant cells orchestrates a dynamic metabolic landscape, fostering the biosynthesis of novel bioactive molecules with functional properties previously untapped in plant biotechnology.
The methodology holds promise not only for industrial bioproduction but also for advancing fundamental scientific understanding of plant-microbe interactions. By leveraging the natural symbiotic mechanisms evolved over millions of years, scientists can decode the complex regulatory networks that govern plant metabolism and immunity, potentially uncovering pathways that modulate stress resistance and secondary metabolite synthesis.
In summary, this pioneering research showcases a sophisticated biological system where endophytic bacteria act as stimulators of plant cell metabolic plasticity without compromising cell viability. The demonstrated capacity to induce dynamic shifts in metabolic profiles lays a robust foundation for future development of bioengineered plant cell cultures as renewable and controllable sources of valuable natural products.
As the agricultural and biotechnological sectors strive to meet the escalating global demand for sustainable natural compounds, the integration of endophytic bacterial co-cultures with plant cell culture platforms represents a compelling frontier. This synergy could ultimately revolutionize the production landscape for pharmaceuticals, nutraceuticals, cosmetics, and eco-friendly agrochemicals, encapsulating a new paradigm of bioinnovation at the interface of plant science and microbiology.
Subject of Research: Cells
Article Title: Plant Immunity–Activating Endophytic Bacteria Induce Dynamic Metabolic Changes in Cultured Plant Cells Without Inhibiting Their Growth
News Publication Date: 8-Jan-2026
References: DOI: 10.1111/1751-7915.70297
Image Credits: Professor Toshiki Furuya from Tokyo University of Science, Japan
Keywords
Plant cells, Green chemistry, Endophytes, Biotechnology, Microorganisms, Metabolites, Metabolic pathways, Biosynthesis
