Dr Marta Berrocal-Lobo | Unlocking the Potential of Essential Oils: Illuminating Epigenetic Effects on Plant Defence Mechanisms

Essential oils (EO) are potent in enhancing plant stress responses and mitigating seed-borne diseases, particularly in high-value crops such as tomatoes. While their direct impacts are recognised, the indirect influences on plant growth, metabolism, and immune responses against phytopathogens remain uncertain. Dr Marta Berrocal-Lobo, an esteemed Associate Professor and researcher at the Polytechnic University of Madrid, in collaboration with the Group of Biopesticides led by Dr Azucena Gonzalez-Coloma, is unravelling the transcriptomic and metabolic responses of tomato seeds treated with an antifungal EO against the pathogen Fusarium oxysporum sp. Their findings pave the way for harnessing EO in sustainable agriculture.

Towards Sustainable Plant Protection: Unveiling the Potential of Artemisia absinthium Oil

Amidst a global imperative to curtail reliance on hazardous pesticides, there is a pressing need for eco-friendly biopesticides. These solutions safeguard agricultural landscapes and vital ecosystems like aquatic habitats and forests. As the world embraces environmentally conscious practices, the quest for natural biopesticides gains momentum, aligning seamlessly with the evolving directives of the European Commission.

Artemisia absinthium is a medicinal herb renowned for its therapeutic properties. The derivative, Artemisia absinthium oil (AEO), exhibits notable antifungal prowess, particularly against notorious phytopathogens like Fusarium species and Botrytis cinerea. Yet, amidst its efficacy lies a realm yet unexplored: the subtle molecular transformations it may induce during plant germination.

Dr Marta Berrocal-Lobo, leading a dedicated team at the R&I Centre for the Conservation of Biodiversity and Sustainable Development at the Polytechnic University of Madrid, is undertaking a pioneering investigation to unravel the intricacies of short- and long-term plant protection and susceptibility stemming from seeds primed with AEO.

Employing the tomato-Fusarium oxysporum sp. lycopersici (Fol) interaction as their model system, they delve into the metabolic and epigenetic transcriptional shifts underpinning disease control and Fol tolerance. This groundbreaking research promises to bolster our understanding of plant defence mechanisms and chart a path towards greener, more resilient agricultural practices.

Artemisia absinthium Oil: Protecting Seed Properties

In collaboration with the esteemed BIOPEST group of the ICA-CSIC, a domesticated variant of Artemisia absinthium (var. Candial) takes centre stage. Through meticulous in vitro testing, the potency of AEO has demonstrated remarkable efficacy in thwarting fungal spore formation.

AEO-coated seeds emerge as guardians of seed integrity, particularly evident in the absence of fungal presence. Notably, AEO-treated seeds exhibit heightened basal production of callose and reactive oxygen species (ROS), fortifying their defences even in pathogen-free environments. This fortified resilience translates into tangible benefits during germination, as AEO-treated seeds showcase enhanced vigour and growth, setting the stage for robust plant development even amidst fungal challenges.

The Resilience of Tomato Plants

Fungal presence poses a formidable threat to the vitality of tomato plants, hindering germination and impeding early shoot and root growth. Compounding the challenge, fungal infection disrupts the plant’s ability to mount crucial immune responses, notably the production of ROS and callose deposition during germination.

Enter AEO: a transformative shield against fungal onslaught. By coating seeds with AEO, researchers observe a remarkable reversal of short-term growth impediments and the initiation of a sustained defence mechanism. Even after 12 days, AEO-treated seeds exhibit elevated levels of ROS and callose, indicative of fortified immunity against fungal intrusion.

Dr Berrocal-Lobo and her esteemed colleagues at CSIC’s Biopest group have looked further into the metabolic and transcriptional landscape of AEO-coated seedlings. Their findings point to a cascade of molecular changes orchestrated by AEO, culminating in enhanced plant resilience. Notably, AEO treatment triggers the production of vital metabolites such as vanillic acid, coumarin, lycopene, and oleamide, renowned for their roles in plant defence and antimicrobial responses. Moreover, transcriptional analyses reveal a concerted upregulation of carotenoid and fatty acid metabolic pathways, signalling a profound adaptation to fungal presence.

In essence, Dr Berrocal-Lobo’s pioneering work underscores the enduring impact of AEO on plant tolerance, offering a beacon of hope for sustainable agriculture in the face of fungal adversity.

Reviving Plant Defences: Reactive Oxygen Species

ROS wield a double-edged sword in plant defence, capable of inducing cell death through apoptosis, a vital mechanism against pathogens. In the face of fungal invasion, the observed decline in ROS production within infected cells is expected. However, a remarkable resurgence of ROS is witnessed in AEO-coated seedlings, attributed to the induced synthesis of lycopene – a potent red carotenoid pigment celebrated for its antimicrobial prowess.

Unravelling Epigenetic Landscapes: Insights from AEO Seed Priming

Concurrently with metabolic shifts, the transcriptional landscape unveils intriguing revelations. Notably, the upregulation of two methyltransferases, pivotal players in the methionine cycle, alongside NRPD2 – an integral component of the DNA methylation pathway reliant on RNA – after 12 days of seed priming signals a profound epigenetic overhaul. Dr Berrocal-Lobo underscores the significance of deciphering these epigenetic signatures, poised to unveil the elusive targets of AEO treatment and the observed enhancement in plant protection. This groundbreaking research paves the path for harnessing ‘directed epigenetic changes’ via seed priming, offering a novel avenue to fortify plant resilience against diseases.

Forging Sustainable Solutions: Environmental Implications of AEO Seed Priming

Dr Berrocal-Lobo and her team champion the pivotal role of seed priming with essential oils in catalyzing transformative epigenetic shifts in crops, bolstering their resilience against formidable phytopathogens. The priming of tomato seeds with AEO not only instigates tolerance to Fusarium oxysporum sp. but also orchestrates a symphony of epigenetic modifications and methylation pathways, fortifying plant defences. These innovative strides hold promise for advancing eco-friendly biopesticides and cultivating plants resilient to environmental stressors, heralding a greener, more sustainable future for agriculture.