The Functional Role of ScGA20 Oxidase in Regulating Sugarcane Growth via Hormonal Pathways

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Sugarcane stands as one of the world’s most vital crops, responsible for producing nearly 80% of global sugar and serving as a key source of biofuel. Despite its agricultural importance, improving sugarcane yields has been a slow and challenging process due to its complex genetic structure.

Traditional breeding methods have struggled to keep pace with growing demands, but a groundbreaking study published in Plant Physiology and Biochemistry in 2025 offers a revolutionary solution.

By genetically modifying sugarcane to overexpress a gene called ScGA20ox, researchers have successfully enhanced the plant’s growth and biomass production.

Role of Gibberellin in Sugarcane Growth

To appreciate the significance of this research, it’s essential to understand the role of gibberellins (GAs), a class of plant hormones that regulate growth processes like stem elongation, seed germination, and flowering.

Gibberellins are chemically classified as diterpenoid acids and are produced in plant tissues such as young leaves, roots, and seeds. They act as molecular signals, triggering cells to divide or elongate, which directly impacts plant height, fruit development, and stress responses.

Among the enzymes involved in GA production, GA20-oxidase (GA20ox) plays a central role. This enzyme catalyzes the final steps of GA biosynthesis, converting inactive forms of the hormone (e.g., GA12 and GA53) into bioactive versions (e.g., GA1 and GA4) that drive growth.

In sugarcane, GA is particularly critical for internode elongation—the process that determines stalk height and, consequently, yield. Internodes are the segments between two nodes (joints) on a sugarcane stalk, and their elongation directly correlates with the plant’s overall biomass.

Despite its importance, the genetic mechanisms controlling GA production in sugarcane have remained poorly understood until now.

Cloning the ScGA20ox Gene: A Technical Breakthrough

The study began by isolating the ScGA20ox gene from a widely cultivated Chinese sugarcane variety, GT42.

• The term “cloning” in this context refers to the process of identifying, copying, and amplifying a specific gene from the plant’s DNA.

The gene, registered under GenBank ID OR283803, consists of 1,167 base pairs—the building blocks of DNA—and encodes a protein of 388 amino acids with a molecular weight of 43.88 kDa (kiloDaltons).

Proteins are large molecules made of amino acids that perform critical functions in cells, and their weight (measured in Daltons) helps scientists understand their structure and role. Detailed analysis revealed that the protein is hydrophilic, meaning it interacts well with water.

This property is quantified by the Grand Average of Hydropathicity (GRAVY) score, a numerical value (-0.440 in this case) that predicts whether a protein will attract or repel water. Researchers also mapped the protein’s 3D structure using computational models, identifying regions critical for its enzymatic activity.

Evolutionary comparisons showed that ScGA20ox shares 96.53% similarity with another GA20ox gene in sugarcane and 93.07% similarity with the corresponding gene in sorghum (Sorghum bicolor), a closely related crop.

These findings highlight the gene’s conserved role across plant species, meaning its function has remained largely unchanged through evolution.

Engineering Transgenic Sugarcane

With the ScGA20ox gene isolated, the next step was to enhance its activity in sugarcane plants. Researchers replaced the gene’s native promoter—a DNA sequence that controls when and where a gene is expressed—with a stronger promoter from maize called Ubi (ubiquitin promoter).

Promoters act like “on switches” for genes, and the Ubi promoter is widely used in plant biotechnology because it ensures high, consistent gene expression across different tissues. To introduce the modified gene into sugarcane cells, the team used a technique called biolistic transformation, often referred to as a “gene gun.”

This method involves coating microscopic gold or tungsten particles with DNA and firing them into plant cells using pressurized gas. The particles penetrate the cell walls and membranes, delivering the DNA into the nucleus, where it integrates into the plant’s genome.

After transformation, the cells were grown on a selection medium containing geneticin, an antibiotic that eliminates non-transformed cells. Geneticin resistance is conferred by a marker gene included in the DNA construct, ensuring only successfully transformed cells survive.

From 100 initial lines, 68 transgenic plants were confirmed through PCR screening, a technique that amplifies specific DNA sequences to verify the presence of the ScGA20ox gene. These plants were then grown in greenhouses alongside wild-type sugarcane to compare their growth and development.

Growth Results: Transgenic vs. Wild-Type Sugarcane

The differences between transgenic and wild-type sugarcane were striking. Within six months, the genetically modified plants reached nearly double the height of their non-modified counterparts.

Shoot dry weight, a measure of biomass obtained by drying plant tissues to remove moisture, was also significantly higher in transgenic lines at two and six months after planting.

For example, at the six-month mark, transgenic sugarcane exhibited a 30% increase in shoot dry weight compared to wild-type plants.

Crucially, the study confirmed that these growth improvements were linked to higher gibberellin levels. Measurements of GA3, a bioactive form of gibberellin, showed concentrations up to 50% greater in transgenic leaves than in wild-type plants.

This direct correlation between ScGA20ox overexpression and GA accumulation underscores the gene’s pivotal role in sugarcane growth.

Unlocking the Molecular Mechanisms

To understand how ScGA20ox influences growth at the molecular level, the researchers conducted a transcriptome analysis—a comprehensive study of gene expression—in both leaves and stems (internodes) of transgenic and wild-type plants.

A transcriptome represents all the messenger RNA (mRNA) molecules in a cell, reflecting which genes are actively being transcribed. By comparing transcriptomes, scientists can identify genes that are upregulated (more active) or downregulated (less active) in response to genetic modifications.

In leaves, 11,505 genes were differentially expressed, with 6,110 upregulated and 5,395 downregulated. In internodes, the changes were even more pronounced, with 23,857 genes showing altered expression levels.

Among these, 10,807 genes were common to both tissues, indicating core pathways driving the observed growth enhancements.

Key Pathways Affected by ScGA20ox Overexpression

One of the most significant findings was the impact on plant hormone signaling pathways. Auxins, another class of plant hormones, regulate cell elongation, root development, and phototropism (growth toward light). In the study, genes responsible for auxin transport, such as AUX1 and LAX, were down regulated by five- to eight fold.

Since auxin regulates cell elongation, this reduction might redirect the plant’s resources toward gibberellin-driven growth. Similarly, ethylene signaling genes like EIN2 and EIN3 were down regulated by three- to five fold.

Ethylene, often called the “stress hormone,” inhibits growth under adverse conditions like drought or flooding. Suppressing its signaling could allow sugarcane to allocate more energy to biomass production.

The study also highlighted changes in photosynthesis-related genes. Photosynthesis is the process by which plants convert sunlight, carbon dioxide, and water into glucose (sugar) and oxygen.

Components of photosystem I (psaA, psaD) and photosystem II (psbO, psbP), which are protein complexes in chloroplasts that capture light energy, were upregulated by five- to eightfold.

Additionally, genes encoding ATP synthase, an enzyme that produces adenosine triphosphate (ATP)—the energy currency of cells—showed increased activity. These changes suggest that transgenic sugarcane generates more energy to fuel rapid growth.

Carbohydrate metabolism pathways were similarly affected. Starch synthase genes (glgA), which promote energy storage by converting glucose into starch, were upregulated by threefold, while sucrose synthase genes (SUS), responsible for breaking down sucrose into glucose and fructose, were downregulated by fourfold.

This shift indicates that transgenic plants prioritize starch production—a temporary energy reserve—over sucrose storage, channeling more resources into growth.

Protein Interaction Networks

The researchers constructed protein-protein interaction (PPI) networks to identify key molecules driving these changes. PPIs are physical contacts between proteins that regulate cellular processes.

• In photosynthesis, proteins like PSAH (a subunit of photosystem I) and PSBQ1 (involved in stabilizing photosystem II) emerged as central hubs, playing critical roles in light absorption and electron transport.
• In starch metabolism, enzymes such as 4-alpha-glucanotransferase (which rearranges starch molecules) and sucrose synthase (which synthesizes sucrose) were pivotal, coordinating the balance between energy storage and growth.

Validation Through qRT-PCR: Confirming the Findings

To ensure the accuracy of their transcriptome data, the team validated eight key genes using quantitative reverse transcription polymerase chain reaction (qRT-PCR), a technique that measures the amount of specific mRNA in a sample.

Unlike RNA sequencing, which analyzes thousands of genes simultaneously, qRT-PCR focuses on individual genes with high precision. The results aligned closely with the RNA sequencing data.

For instance, c98530_g1 (a gene involved in steroid biosynthesis) was upregulated 2.5-fold in transgenic leaves, while c77163_g1 (linked to cell expansion) showed an 8.5-fold increase. Conversely, c95393_g2 (related to nitrogen metabolism) was downregulated 5.8-fold. These validations reinforce the study’s reliability.

Implications for Agriculture and Beyond

The implications of this research are far-reaching. For farmers, transgenic sugarcane could mean higher yields on the same amount of land, boosting both sugar and biofuel production.

Enhanced photosynthesis and energy efficiency might also make crops more resilient to environmental stressors like drought or poor soil conditions—a critical advantage as climate change intensifies.

Beyond sugarcane, this study offers a blueprint for improving other crops. Rice, maize, and wheat, which rely on gibberellin for growth, could benefit from similar genetic modifications.

For instance, overexpressing GA20ox in rice has already been shown to increase plant height and yield in earlier studies. By applying these strategies, scientists could help address global food insecurity and support sustainable agriculture.

Challenges and Considerations

Despite its promise, the study acknowledges several challenges. The cost of biolistic transformation, for example, remains high, limiting accessibility for small-scale farmers in developing regions. Cheaper alternatives, such as CRISPR-based gene editing, could democratize this technology.

CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) is a precise gene-editing tool that allows scientists to add, remove, or alter DNA sequences at specific locations in the genome. Unlike biolistics, CRISPR does not require foreign DNA insertion, which might ease regulatory approval and public acceptance.

Additionally, ecological risks must be carefully managed. Field trials are necessary to ensure transgenic sugarcane does not outcompete native vegetation or disrupt local ecosystems.

Ethical considerations, including data privacy (protecting genetic information) and public acceptance of genetically modified organisms (GMOs), also require attention. Transparent communication and robust regulatory frameworks will be essential to build trust and ensure responsible innovation.

Future Directions

Looking ahead, the researchers emphasize the need for further studies to address unanswered questions. For instance, how does ScGA20ox interact with other genes, such as ScNAC23 or ScGAI, which are known to influence sugarcane development?

ScNAC23 is a transcription factor regulating stress responses, while ScGAI encodes a DELLA protein that inhibits GA signaling. Understanding these interactions could refine strategies for yield improvement.

Field trials under real-world conditions will also be crucial to validate greenhouse results and assess long-term impacts. Factors like pest resistance, water usage, and soil health must be evaluated to ensure transgenic sugarcane performs well in diverse environments.

Another priority is exploring low-cost solutions for farmers. While biolistics is effective, it requires specialized equipment. Developing simpler, more affordable transformation methods could accelerate adoption in resource-limited settings.

Conclusion

This study represents a landmark achievement in plant biotechnology. By harnessing the power of the ScGA20ox gene, scientists have unlocked a pathway to faster growth, higher yields, and greater resource efficiency in sugarcane.

While challenges remain, the fusion of genetic engineering and traditional breeding offers hope for a more sustainable agricultural future. As the world grapples with climate change and population growth, innovations like this underscore the vital role of science in securing global food systems.