A novel method for stabilising infectious clones of circular single-stranded DNA viruses could reshape how agricultural researchers in China and beyond study and combat some of the world’s most persistent plant pathogens.
Researchers studying the Tomato yellow leaf curl China virus (TYLCCNV), a major agricultural threat and a key model for circular single-stranded DNA (cssDNA) viruses, have long wrestled with a frustrating technical problem. The infectious clones used to study these viruses in the lab are inherently unstable. They are typically constructed as two tandem copies of the small viral genome within Agrobacterium-based vectors, but successive cultivation often leads to a reduction or complete loss of virulence in host plants. This instability, the team discovered, is mechanistically analogous to the virus’s own replication process, driven by the activity of the viral Replication protein (Rep) and the replication origins.
The challenge was that unlike RNA viruses, which can use introns to disrupt toxic protein sequences for stabilization, DNA viruses cannot remove introns before releasing their genomes. The solution, published in Plant Biotechnology Journal, is elegantly borrowed from cellular repair biology. The team developed a micro-homology mediated end joining (MMEJ)-based system. They disrupted the Rep coding sequence with an I-SceI site flanked by microhomologous regions, which stabilises the clone in prokaryotic cells. Then, when the construct is introduced into a plant host, a transiently co-expressed I-SceI enzyme excises the site, and the plant’s own MMEJ repair machinery seamlessly restores a functional viral genome.
Why it matters:
This work addresses a fundamental bottleneck in plant virology that has likely hindered progress for years. By providing a stable, reliable method for constructing infectious clones, it opens the door to more systematic studies of cssDNA virus biology and resistance mechanisms. For China, a major agricultural producer where TYLCCNV and related viruses cause significant economic losses, this methodological advance could accelerate the development of resistant crop varieties and more effective disease management strategies.
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