Temporal multi-omics dataset of a cucurbit–powdery mildew interaction

In the hidden world of plant life, a constant, silent war is waged between crops and the microscopic fungi that seek to consume them. Among the most persistent invaders are powdery mildews, a group of fungi that cannot survive on their own. Unlike many other plant diseases that can be grown in a lab dish, these fungi are obligate biotrophs, meaning they must live inside the living tissue of a host plant to complete their life cycle. They send out tiny, specialized feeding structures that penetrate plant cells, siphoning off nutrients while simultaneously releasing chemical signals to quiet the plant's immune system. This intimate, parasitic relationship makes them incredibly difficult to study in isolation, as removing them from the plant kills them. For farmers, these fungi are a major threat; they infect thousands of plant species, including the melons, cucumbers, and squashes that feed people around the globe. Because the fungi are so dependent on their hosts, traditional methods of controlling them with chemical sprays often fail as the fungi quickly evolve resistance, leaving crops vulnerable to severe damage and economic loss.

To understand how to protect these crops, scientists need to see the battle unfold in real time, capturing not just the genetic instructions the fungi and plants use, but also the chemical changes happening inside the leaves as the infection progresses. Until now, most studies have offered only a few snapshots of this process, often looking at just one type of data, such as which genes are active. A new study by researchers in Spain has changed this by creating a detailed, time-resolved map of the entire interaction between a melon plant and the powdery mildew fungus that attacks it. By collecting leaf samples every twelve hours over six days, the team generated a massive dataset that tracks both the genetic activity and the chemical composition of the plant and fungus simultaneously. This resource allows scientists to watch how the fungus reprograms the plant's metabolism step by step, revealing the precise moments when the pathogen takes control and how the plant attempts to fight back.

The researchers focused on a specific strain of powdery mildew, known as Podosphaera xanthii, which is a primary cause of disease in melon crops. They grew melon plants in a controlled environment and sprayed them with a suspension of fungal spores, while a separate group of plants received only a harmless liquid spray to serve as a comparison. Over a period of 144 hours, they harvested leaves from both groups at twelve different time points, ensuring they captured every stage of the fungal life cycle, from the initial landing of a spore to the full growth of fungal threads and the production of new spores. From these leaves, they extracted two types of information: the genetic code being read by the cells, known as transcriptomics, and the thousands of small molecules present in the tissue, known as metabolomics. Because they used the exact same leaf samples for both analyses, they could directly link changes in gene activity to specific chemical shifts, creating a unified picture of the infection.

The resulting data reveals a dynamic and shifting landscape. As the hours passed, the researchers observed a clear transition in the leaf's composition. In the early stages, the genetic material found in the samples came almost entirely from the melon plant. However, as the fungus established itself and spread, the proportion of fungal genetic material grew steadily, eventually making up nearly one-fifth of the total genetic material in the leaf by the end of the experiment. This shift mirrored what the scientists saw under a microscope, where the fungal structures became increasingly dense and widespread. The genetic analysis showed that the fungus was not merely sitting on the leaf but was actively rewriting the plant's instructions, turning on genes related to nutrient transport and suppressing those involved in defense. At the same time, the chemical analysis showed that the plant was undergoing a massive metabolic overhaul. The levels of specific compounds, particularly those involved in the plant's defense systems and stress responses, rose and fell in a coordinated pattern that tracked the progression of the disease.

One of the most significant findings is the identification of specific chemical pathways that the fungus exploits. The data highlighted that the plant's production of certain defense-related chemicals, such as those derived from phenylpropanoid pathways, was heavily influenced by the infection. These are the same types of compounds that plants often use to build physical barriers or send warning signals to neighboring cells. The study also showed that the fungus manipulates amino acid metabolism, likely to secure the nitrogen and carbon it needs to grow. By mapping these changes across the entire six-day period, the researchers were able to pinpoint when the fungus shifted from an initial invasion phase to a phase of rapid growth and reproduction. This level of detail was previously unavailable because earlier studies often relied on fewer time points or looked at only one type of data, missing the connection between the genetic commands and the chemical results.

The value of this work extends beyond just understanding this specific fungus and melon. The dataset is now publicly available for other scientists to use, offering a comprehensive resource for studying how obligate biotrophs operate. Because the data includes both genetic and chemical information from the same samples, it allows researchers to build more accurate models of how these pathogens suppress plant immunity. This is crucial for developing new strategies to protect crops, as it moves beyond simply observing that a plant is sick to understanding the exact molecular mechanisms the fungus uses to cause that sickness. The study confirms that the interaction is a complex, time-dependent process where the fungus actively reprograms the host, and it provides the detailed evidence needed to find new ways to interrupt that process. By making this information open to the global scientific community, the researchers hope to accelerate the discovery of more effective and sustainable ways to manage powdery mildew, ensuring that crops remain healthy in the face of these persistent and evolving threats.