Secondary Metabolites and Their Role in Strawberry Defense

Abstract

Strawberry is a high-value commercial crop and a model for the economically important Rosaceae family. Strawberry is vulnerable to attack by many pathogens that can affect different parts of the plant, including the shoot, root, flowers, and berries. To restrict pathogen growth, strawberry produce a repertoire of secondary metabolites that have an important role in defense against diseases. Terpenes, allergen-like pathogenesis-related proteins, and flavonoids are three of the most important metabolites involved in strawberry defense. Genes involved in the biosynthesis of secondary metabolites are induced upon pathogen attack in strawberry, suggesting their transcriptional activation leads to a higher accumulation of the final compounds. The production of secondary metabolites is also influenced by the beneficial microbes associated with the plant and its environmental factors. Given the importance of the secondary metabolite pathways in strawberry defense, we provide a comprehensive overview of their literature and their role in the defense responses of strawberry. We focus on terpenoids, allergens, and flavonoids, and discuss their involvement in the strawberry microbiome in the context of defense responses. We discuss how the biosynthetic genes of these metabolites could be potential targets for gene editing through CRISPR-Cas9 techniques for strawberry crop improvement.

Keywords: allergens; beneficial microbes; flavonoids; metabolites; pathogens; strawberry diseases; terpenes.

Figure 1

A phylogenetic tree of Fragaria vesca terpene synthase genes classified based on Solanum lycopersicum terpene synthases. The phylogenetic tree was constructed in the MEGA 10.1.7 (Molecular Evolutionary Genetics Analysis) program using the maximum likelihood method, with the protein sequence alignment as input. Bootstrap values were calculated from 1000 independent bootstrap runs.

Figure 2

A phylogenetic tree of Fragaria vesca PR-10 allergen genes including the newly identified ones in this review. The phylogenetic tree was constructed in the MEGA 10.1.7 (Molecular Evolutionary Genetics Analysis) program using the maximum likelihood method, with the protein sequence alignment as input. Bootstrap values were calculated from 1000 independent bootstrap runs.

Figure 3

Beneficial microbial composition of the above-ground and below-ground compartments of strawberry. This figure was created with BioRender.com.

Figure 4

Dynamics of strawberry microbiome in the rhizosphere. The potential fungal antagonists are highlighted in dark cyan. This figure was created with BioRender.com.