Plants have a unique ability to repair and regenerate damaged tissues, a trait that humans have harnessed for centuries through practices like grafting and cuttings.
Today, this natural regenerative ability is at the heart of plant genetic transformation—a process that introduces new genes into plants to improve traits such as drought tolerance, pest resistance, and nutritional quality.
Since the first genetically modified (GM) crop was developed in 1983, over 200 transgenic plant species, including rice, maize, and soybeans, have been created.
These innovations are critical for addressing global challenges like food security and climate change. However, many plants, especially complex species like trees and algae, struggle to regenerate after genetic modification.
Understanding Genetic Transformation Methods
One of the most widely used techniques is Agrobacterium-mediated transformation. This method relies on a soil bacterium, Agrobacterium tumefaciens, which naturally transfers part of its DNA into plants.
Scientists replace the bacterium’s native genes with desired ones, enabling plants to express new traits. For example, this method has achieved up to 78.8% efficiency in apple and kiwifruit by targeting their hairy roots.However, it works poorly in many crops like rice and wheat.
Researchers developed the GiFT (Genotype-independent Fast Transformation) method, which uses germinated soybean seeds and ultrasound to produce transgenic plants in weeks, bypassing lengthy tissue culture steps.
Another popular approach is microprojectile bombardment, often called the “gene gun.” This technique shoots DNA-coated metal particles into plant cells, allowing genes to integrate into the genome.
While effective for algae and chloroplast engineering, it suffers from low efficiency (often below 5%) and high costs. For instance, transforming algae like Chlamydomonas reinhardtii requires precise adjustments to avoid damaging cells.
A simpler yet less efficient method is the pollen-tube pathway, where DNA is injected into plant ovaries after pollination. The pollen tube acts as a natural conduit, delivering genes to fertilized egg cells.
This approach avoids complex lab procedures and has been used successfully in crops like cotton and melons. In orchids, it achieved a 2.54% success rate.
Recent innovations include using magnetic nanoparticles to deliver genes into pollen grains. After pollination, these particles help produce transgenic seeds naturally. Though still debated, this method shows promise for crops like maize and peppers.
Similarly, the cutting-dip-budding (CDB) method involves dipping cut plant stems in Agrobacterium solutions and growing them on vermiculite. This approach works well for sweet potatoes and certain trees, with a 3.3% shoot regeneration rate in apples.
Overcoming Challenges in Complex Species
Transforming woody plants like pine, poplar, and tea remains difficult due to their long life cycles and low regeneration rates.
For example, poplar trees achieve 32.18% transformation efficiency using young leaves , while sweet cherry struggles at 1.2% .
Rooting tissue-cultured saplings is another hurdle, with species like Populus tomentosa often failing to develop strong roots.
Algae, particularly microalgae like Chlamydomonas, are easier to manipulate due to their rapid growth. Gene guns and glass beads are commonly used here.
CRISPR editing has also made waves—deleting the glgC gene in cyanobacteria increased succinate production by 50%, showcasing algae’s potential for biofuels.
The Role of Hormones and Key Genes
Plant hormones like auxin and cytokinin play central roles in regeneration. Auxin drives root formation, while cytokinin promotes shoot growth. Balancing these hormones in tissue culture media is critical.
For example, synthetic auxins like 2,4-D are potent but can disrupt normal growth if overused. Jasmonic acid (JA), another key hormone, triggers wound healing and root regeneration by activating genes like ERF109 .
Genes such as Baby Boom (BBM) and Wuschel (WUS) act as “regeneration accelerators.” Overexpressing these genes in maize boosted transformation rates by 15-fold.
Similarly, the GRF-GIF complex enhanced regeneration in wheat to 48.7% . These breakthroughs reduce reliance on specific plant varieties, making genetic engineering more accessible.
Current Challenges and Solutions
Despite progress, challenges persist. Genotype dependency limits many methods to specific plant varieties—70% of maize lines resist transformation.
Solutions include combining BBM and WUS genes to override genetic barriers. Malformations during tissue culture, such as sterile or stunted plants, remain common. Researchers found that mutations in the HY5 gene impair shoot regeneration, offering clues to improve protocols.
Long transformation cycles are another issue. For example, modifying cotton takes 18 months. However, the Successive Regeneration Acclimation (SRA) strategy, which reuses regenerated seeds, reduced timelines by 30%.
Future Directions and Innovation
Looking ahead, pollen-mediated transformation using magnetic nanoparticles could simplify the process by enabling “direct seeding” of transgenic crops.
Meanwhile, single-cell sequencing is uncovering hidden details of regeneration. A study mapping 7,552 Arabidopsis root cells revealed that the WOX13 gene inhibits regeneration, providing new targets for improvement.
Spatial transcriptomics is another game-changer. By tracking gene activity in intact tissues, scientists identified five cell types in tomato callus during bud regeneration .
Additionally, epigenetic engineering—adjusting DNA methylation—could restore regeneration capacity in aged cells, opening doors to transform older plants.
Conclusion
Plant genetic transformation has come a long way, yet challenges like genotype dependency and inefficiencies remain.
By integrating hormonal insights, key genes like BBM, and cutting-edge tools like CRISPR and spatial transcriptomics, researchers are making strides toward universal transformation protocols.
These advancements will be vital for designing crops that withstand climate extremes, pests, and diseases, ensuring sustainable agriculture for future generations.
Wang, P., Si, H., Li, C., Xu, Z., Guo, H., Jin, S., & Cheng, H. (2025). Plant genetic transformation: Achievements, current status and future prospects. Plant Biotechnology Journal, 24(1), 1–25. https://doi.org/10.1111/pbi.70028Reference:
