麻豆淫院

In a development that could help protect one of the world's most beloved agricultural commodities, a research team at Penn State has successfully created disease-resistant cacao plants using gene-editing technology. According to the researchers, the innovation promises to help resolve a significant problem for the global chocolate industry, worth more than , which faces threat from the phytophthora species, a fungal-like pathogen that gives rise to the destructive black pod disease that can cause yield losses of up to .

In recently posted online in Plant Biotechnology Journal in advance of print publication this fall, the researchers reported that they edited the gene TcNPR3 in cacao plants, ultimately resulting in cacao plants that had 42% smaller disease lesions when infected with phytophthora, compared to non-edited plants.

"Cacao farmers, particularly those with limited economic resources, struggle to implement expensive disease-control measures," said team leader Mark Guiltinan, professor of plant molecular biology in the College of Agricultural Sciences and first author on the study. "And many genetic modification approaches are met with stigma because foreign DNA is left in the final product. Our approach could solve both of those problems."

The researchers employed CRISPR-Cas9, a gene editing technology that acts like "molecular scissors" to precisely modify DNA sequences in the genome, or the complete instructions encoding proteins and more, of living cells and organisms. This usually works by cutting unwanted genes out of the genome and splicing in transgenes, which are genes from other organisms or modified in the lab to achieve the desired functionality.

However, this breakthrough represents the first demonstration of genome-edited, transgene-free cacao plants, meaning the plant's DNA was altered without leaving any foreign DNA in the final product, addressing regulatory concerns and consumer acceptance.

The team specifically edited the gene TcNPR3, which is involved in the plant's defense system, in plant cells, grew the cells into full plants and confirmed that they were less susceptible to the disease in lab tests using plant leaves, called foliar assays. The team crossed these edited plants with non-transgenic鈥攏ormal cacao plants鈥攔esulting in non-transgenic offspring with the desired genetic changes.

The researchers sequenced the genomes of parent and offspring plants and found that some offspring retained the beneficial gene edit but no longer had any foreign DNA鈥攖hey were "clean" edits. The researchers analyzed the clean edits' gene expression and found increased expression of genes involved in plant defense, with some genes downregulated, suggesting TcNPR3 may both suppress and activate certain genes.

"Our research team targeted the gene TcNPR3 because we learned from earlier studies that it acts as a molecular 'brake' on the plant's natural defense system," Guiltinan said. "NPR3 proteins鈥攖he family to which TcNPR3 belongs鈥攁re negative regulators of plant immunity, essentially preventing plants from mounting robust defenses against pathogens when they're not immediately under attack."

Think of NPR3 as a security system that's set to "standby mode," he explained. Disrupting the gene turns on its "high alert" mode, increasing the plant's natural defenses and making the plant less susceptible to pathogen attacks.

Perhaps more novel than using CRISPR-Cas9 technology to precisely mutate the TcNPR3 gene, Guiltinan said, was using traditional plant breeding to eliminate the foreign DNA sequences associated with the gene-editing machinery.

The result鈥攃acao plants that contain only the desired genetic modifications without any transgenic elements鈥攅stablishes a significant regulatory precedent, Guiltinan said, because the U.S. Department of Agriculture (USDA) has determined that these edited plants are not subject to biotechnology regulations since they contain no foreign genetic material鈥攐nly precise edits to native cacao genes.

After review of extensive data in the study manuscript, the USDA officially stated that it does not consider the genome-edited cacao lines to meet the same regulation requirements as genetically modified plants. However, the plants may still come under regulation by the U.S. Food and Drug Administration, Guiltinan said, "but that is down the line."

This regulatory clarity removes a major barrier to adoption, Guiltinan suggested, adding that next the team will have to test the lines outside on research stations in tropical areas.

"We need to assess the plants' performance outside of our greenhouses," he said. "If successful, our hope is that someday soon, farmers and consumers can benefit from these disease-resistant plants to improve their livelihoods and protect the environment."

Guiltinan and his team are assessing additional targets to increase disease resistance, as well as exploring new methods of genome editing, with the goal of developing a second generation of genome-edited cacao lines in the coming years.

"We're not just creating better cacao plants鈥攚e're exploring how modern biotechnology can work within existing regulatory frameworks to address real-world agricultural challenges," Guiltinan said. "Traditional breeding approaches are slow, often taking decades to develop new resistant varieties.

"For the millions of farmers who depend on cacao cultivation, and the billions who enjoy chocolate, this research offers hope for a more sustainable and secure future鈥攐ne precise genetic edit at a time."

Other members of the team contributing to the research were: Lena Landherr, assistant research professor in plant science; Siela Maximova, research professor of plant biotechnology and co-director of the Endowed Program in the Molecular Biology of Cocoa at Penn State's Huck Institutes of the Life Sciences; Dante DelVecchio, graduate student in plant science; Aswathy Sebastian, bioinformatics analyst at the Huck Institutes; and Istvan Albert, research professor of bioinformatics at the Huck Institutes.