Unveiling the role of strigolactones in strawberry fruit development
Imagine a hormonal signal so powerful that it influences how plants grow, interact with fungi, avoid pests, and develop their fruits—all while remaining virtually unknown to most people. Meet strigolactones, the relatively newly discovered plant hormones that are rewriting our understanding of fruit development. While most food enthusiasts can describe how sunlight and soil affect their favorite fruits, few realize that an intricate hormonal conversation within the plant determines whether those fruits develop properly in the first place.
Once known only for their role in helping parasitic plants locate victims, strigolactones have emerged as master regulators of plant architecture and development. But their most tantalizing role might be in fruit development—a discovery that could transform how we grow crops.
Recent groundbreaking research on woodland strawberries has uncovered that these hormones act as crucial conductors in the early symphony of fruit formation 1 2 . This article unveils the hidden world of strigolactones and explores how scientists discovered their surprising role in giving us one of summer's sweetest treasures: the strawberry.
Strigolactones have a fascinating history that reveals their multifaceted nature. First discovered in 1966 when scientists isolated "strigol" from cotton root exudates, these compounds were initially noted for their ability to stimulate germination of parasitic weeds like Striga and Orobanche 3 . It wasn't until 2005 that researchers discovered their positive role in promoting symbiotic relationships with arbuscular mycorrhizal fungi, which help plants absorb nutrients from the soil 3 . The big breakthrough came in 2008 when strigolactones were recognized as a new class of plant hormones that inhibit shoot branching 2 5 .
These remarkable compounds are derived from carotenoids and belong to the terpene lactone family. Their biosynthesis follows a carefully orchestrated pathway:
CCD7 and CCD8 enzymes sequentially cleave this molecule to produce carlactone, the precursor to all known strigolactones 3
MAX1 and LBO enzymes then modify carlactone into various strigolactone forms 1
The signaling pathway is equally sophisticated. When strigolactones are present, they bind to the D14 receptor protein, which then teams up with D3 protein to form a complex that tags the D53 repressor protein for destruction 2 . This removal of D53 allows genes responsible for implementing strigolactone's instructions to be expressed, ultimately affecting everything from branch suppression to fruit development 2 5 .
Strigolactones are derived from carotenoids through a multi-step enzymatic process involving D27, CCD7, CCD8, MAX1, and LBO enzymes.
The D14 receptor binds strigolactones, forming a complex with D3 that degrades the D53 repressor, allowing gene expression.
When scientists decided to investigate strigolactones in fruit development, they turned to the woodland strawberry (Fragaria vesca). This choice was strategic—while commercial strawberries are complex octoploids (with eight sets of chromosomes), the woodland strawberry is diploid with a compact, fully sequenced genome of just 240 Mb 1 8 . This genetic simplicity, combined with its ease of transformation, has made it an ideal model organism for studying rosaceae plants and non-climacteric fruits (those that don't ripen after picking) 1 .
Compact 240 Mb genome makes genetic analysis more straightforward
Simplifies genetic modification for experimental purposes
The strawberry's unique structure also makes it particularly interesting for developmental studies. What we consider the "fruit" is actually the swollen receptacle tissue, with the true fruits being the tiny achenes (commonly called seeds) dotting its surface 8 . This complex development requires precise hormonal coordination, making it an excellent system for investigating strigolactone involvement.
To unravel the connection between strigolactones and fruit development, scientists employed a comprehensive approach combining genomics and expression analysis 1 2 . Their methodology can be broken down into several key stages:
| Step | Methodology | Purpose |
|---|---|---|
| Gene Identification | Bioinformatics analysis of woodland strawberry genome | Identify genes similar to known SL biosynthetic and signaling genes from rice and Arabidopsis |
| Phylogenetic Analysis | Construction of evolutionary trees using protein sequences | Verify conserved function of identified genes across plant species |
| Motif Analysis | MEME software to identify conserved protein motifs | Confirm functional importance of identified genes |
| Expression Profiling | RNA sequencing across different tissues and developmental stages | Determine where and when SL genes are active during fruit development |
The research team successfully identified a full suite of strigolactone genes in the woodland strawberry genome: one D27, two MAX1, and one LBO gene for biosynthesis, and one D14, one D3, and two D53 genes for signaling 1 2 . But the truly fascinating insights emerged when they examined where and when these genes were active.
| Tissue/Development Stage | SL Biosynthetic Genes | SL Signaling Genes | Interpretation |
|---|---|---|---|
| Vegetative tissues (root, stem, leaf) | Variable expression levels | Variable expression levels | SLs have roles beyond fruit development |
| Flower organs (carpel, anther, style) | High expression | High in carpel/style, low in anther | Active SL production and signaling in female reproductive tissues |
| Receptacle after pollination | Significantly increased | Significantly increased | SLs likely important in initial fruit set |
| Receptacle during development | Gradual decrease | Gradual decrease | SL importance declines as fruit matures |
| Ripening fruits | Low or no expression | Low or no expression | SLs not involved in late ripening processes |
The spatial analysis revealed that strigolactone biosynthesis and signaling are particularly active in the developing carpel and style of flowers, suggesting these hormones play special roles in the female reproductive structures 1 . The temporal patterns, however, told an even more compelling story: both biosynthetic and signaling genes experienced a significant surge in activity in the receptacle immediately after pollination, then gradually declined throughout fruit development 1 2 .
Perhaps most strikingly, the researchers detected little to no expression of these genes in fully ripening fruits 1 2 5 . This clear pattern suggests that strigolactones are primarily involved in the early stages of fruit development rather than the ripening process itself.
Interactive chart showing strigolactone gene expression patterns during strawberry development would appear here
Studying elusive compounds like strigolactones requires specialized tools and methods. Researchers in this field rely on an array of sophisticated techniques to detect, analyze, and manipulate these signaling molecules.
| Tool/Reagent | Function/Application | Significance |
|---|---|---|
| GR24 | Synthetic strigolactone analog | Used to apply SL treatment and rescue mutant phenotypes |
| HPLC/UHPLC-MS/MS | Analytical chemistry tool for separation and detection | Enables identification and quantification of SLs at extremely low concentrations |
| Stable isotope-labeled analogs | Internal standards for quantification | Allows precise measurement of SL levels in plant tissues |
| CRISPR/Cas9 | Genome editing system | Creates SL gene knockouts to study function |
| RNA sequencing | Transcriptome analysis | Measures gene expression patterns across tissues and developmental stages |
The development of increasingly sensitive mass spectrometry techniques has been particularly revolutionary, allowing scientists to detect strigolactones at attomolar concentrations—akin to finding a single specific grain of sand scattered across a massive beach 3 . Meanwhile, synthetic analogs like GR24 provide vital tools for testing strigolactone functions without relying on the plant's own production, which is often minimal and tissue-specific 3 .
The discovery that strigolactones participate in strawberry fruit development opens exciting new avenues for both basic science and agricultural innovation. Understanding these hormonal pathways could lead to strategies for improving fruit set, enhancing yields, and potentially modifying fruit characteristics in strawberries and other crops.
The implications extend beyond strawberries—similar mechanisms may operate in other fruits, suggesting strigolactones could represent a previously overlooked regulatory layer in fruit development across species. This research also demonstrates how much we have yet to learn about plant hormonal networks and their intricate interplay.
Recent applications of strigolactone research highlight its practical potential. A 2025 study published in Cell identified two strigolactone transporter genes in sorghum that, when knocked out, reduced Striga infestation by 67-94% and cut yield losses by approximately half 7 . This breakthrough demonstrates how understanding strigolactone biology can lead to real-world solutions for major agricultural challenges.
As research continues, scientists are increasingly viewing strigolactones not just as simple hormones but as versatile communication tools that help plants manage their growth, interact with their environment, and successfully reproduce—all processes that ultimately determine whether we enjoy a bountiful harvest or a sparse one.
The story of strigolactones in strawberry fruit development reminds us that nature's most important processes often occur behind the scenes, visible only to those who know where to look. Through meticulous genetic detective work, scientists have uncovered how this once-obscure class of plant hormones helps orchestrate the early development of one of our most beloved fruits.
The next time you bite into a plump, red strawberry, consider the invisible hormonal symphony that made it possible—a complex performance where strigolactones help conduct the crucial opening movements. As research continues to unravel these subtle hormonal conversations, we gain not only a deeper appreciation for plant biology but also powerful new approaches to improving the fruits that sustain and delight us.