Microscopic view of powdery mildew fungi consuming lipid molecules on a plant leaf.

The Great Fungal Diet: How Mildew Survives by Bypassing Carbs

Theo Raines in Science & Nature August 2025 • 4 min read.

"Scientists Uncover How Powdery Mildew Thrives on Fats, Rewriting Rules of Fungal Nutrition"

Powdery mildew is a plant disease that causes devastating damage to plants. Obligate biotrophic fungal pathogens are responsible for this widespread condition, which involves intricate species-specific interactions between the host and the parasite.

Researchers have long sought to understand the mechanisms that allow these fungi to thrive, focusing on how they acquire nutrients from their hosts. Traditionally, it was believed that carbohydrates were the primary source of energy for these pathogens. However, new research is turning this understanding on its head.

A new study analyzing 15 microbial genomes, including various powdery and downy mildews and rusts, reveals a surprising adaptation: powdery mildews have undergone a massive contraction of genes related to carbohydrate metabolism while maintaining the integrity of their fatty acid metabolism pathways. This suggests that powdery mildews have evolved to rely more on lipids (fats) for survival.

The Carbohydrate Cutback: How Mildew Evolved to Eat Fats

Microscopic view of powdery mildew fungi consuming lipid molecules on a plant leaf.

The study reveals that powdery mildews exhibit a genome-wide reduction in multiple gene families, especially those involved in carbohydrate metabolism. When compared with other ascomycete phytopathogens, powdery mildews show a distinct lack of enzymes needed to break down and process carbohydrates.

This discovery challenges the conventional wisdom that carbohydrates are the primary energy source for these fungi. Instead, the researchers found that the fatty acid metabolism pathway remains intact and functional in powdery mildews, indicating a shift towards using lipids as a main source of nutrition.

Contracted Carbohydrate Metabolism: Powdery mildews have fewer genes related to breaking down carbohydrates.
Intact Fatty Acid Metabolism: The fungi maintain the genes necessary for processing fats.
Comparative Genomics: Analysis of 15 microbial genomes reveals this unique adaptation in powdery mildews.

To confirm these findings, the team analyzed the core set of orthologous families present in various ascomycete pathogens. They confirmed the presence of genes enriched for energy metabolism and primary signaling pathways, but noted a significant reduction in carbohydrate metabolism-related genes. Further analysis revealed that key components for degrading plant cell walls, such as pectin, were also reduced, suggesting that powdery mildews have a decreased ability to break down plant cells for nutrients, shifting the need of energy source.

What This Means for the Future of Plant Disease Control

This discovery could pave the way for new strategies in plant disease control. By understanding how powdery mildews have adapted their metabolism, researchers can target these specific pathways to disrupt the fungus's ability to thrive. For example, treatments could be developed to interfere with lipid metabolism, effectively starving the fungus and preventing disease.

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This article is based on research published under:

DOI-LINK: 10.3389/fmicb.2018.03160, Alternate LINK

Title: Powdery Mildews Are Characterized By Contracted Carbohydrate Metabolism And Diverse Effectors To Adapt To Obligate Biotrophic Lifestyle

Subject: Microbiology (medical)

Journal: Frontiers in Microbiology

Publisher: Frontiers Media SA

Authors: Peng Liang, Songyu Liu, Feng Xu, Shuqin Jiang, Jun Yan, Qiguang He, Wenbo Liu, Chunhua Lin, Fucong Zheng, Xiangfeng Wang, Weiguo Miao

Published: 2018-12-18

Everything You Need To Know

How does powdery mildew obtain its nutrients, and what makes it different from other fungi?

Powdery mildew, unlike many other fungi, has adapted to primarily use lipids (fats) for nutrition rather than carbohydrates. This adaptation involves a significant reduction in genes related to carbohydrate metabolism and the preservation of fatty acid metabolism pathways. This shift allows powdery mildew to thrive by extracting fats from its host plants, making it unique among ascomycete phytopathogens. It is important to note that obligate biotrophic fungal pathogens establish species-specific interactions between the host and the parasite.

What specific changes have occurred in powdery mildew's genome to support its fat-based diet?

The genome of powdery mildew shows a substantial reduction in multiple gene families associated with carbohydrate metabolism. Enzymes needed to break down and process carbohydrates are notably lacking. Conversely, the fatty acid metabolism pathway in powdery mildew remains intact and functional, enabling the fungus to efficiently process and utilize lipids. Furthermore, key components for degrading plant cell walls, such as pectin, are also reduced, indicating a decreased reliance on breaking down plant cells for nutrients.

What was the methodology used to discover that powdery mildew relies on fats instead of carbohydrates?

Researchers analyzed 15 microbial genomes, including various powdery and downy mildews and rusts, using comparative genomics. They compared the core set of orthologous families present in various ascomycete pathogens and noted a significant reduction in carbohydrate metabolism-related genes in powdery mildews. This analysis highlighted the contraction of genes related to carbohydrate metabolism and the maintenance of fatty acid metabolism pathways, suggesting a shift towards lipid utilization.

How might the discovery of powdery mildew's fat-based diet influence future strategies for plant disease control?

Understanding that powdery mildew relies on lipid metabolism opens new avenues for plant disease control. Treatments could be developed to specifically target and disrupt the fungus's lipid metabolism pathways. By interfering with the fungus's ability to process fats, these treatments could effectively starve the powdery mildew, preventing or mitigating disease. The focus would be on disrupting the integrity of their fatty acid metabolism pathways.

What are the implications of powdery mildew's adaptation to lipid metabolism for our broader understanding of fungal nutrition and plant-pathogen interactions?

Powdery mildew's adaptation to lipid metabolism challenges the conventional understanding that carbohydrates are the primary energy source for all fungi. This discovery highlights the evolutionary flexibility of fungi and their ability to adapt to different nutrient sources based on their environment. Further research into the specific mechanisms of lipid uptake and metabolism in powdery mildew could reveal new insights into plant-pathogen interactions, potentially leading to a more comprehensive understanding of how pathogens acquire nutrients from their hosts. Also, it might help understand the species-specific interactions between the host and the parasite.