Penn State Study Reveals Plant Virus Interaction Effects

By Blake Jackson

Like people, plants can be infected by more than one virus at a time, which can lead to more severe illnesses or even the emergence of new variants. However, these mixed infections remain poorly understood.

A Penn State research team studied how two common plant viruses tomato spotted wilt orthotospovirus (TSWV) and impatiens necrotic spot orthotospovirus (INSV) interact when infecting the same plant.

Their findings, published in Viruses, revealed that plants with both viruses had significantly lower levels of TSWV compared to plants infected with TSWV alone. INSV levels, however, remained higher, suggesting an antagonistic interaction between the two.

“Ours is the first study that looked at these mixed infections,” said Cristina Rosa, professor of plant virology at Penn State. “The knowledge generated here could eventually be used in management of plant viruses transmitted by vectors if the plant pathways identified in this study can be manipulated to help in control disease in plants. Theoretically this approach could result in economic benefits for growers.”

Although TSWV and INSV were once considered the same species, they are now recognized as separate viruses with similar genomic and ecological traits. Both infect a wide range of plants, cause necrosis, and are spread by thrips tiny insects that puncture plants to feed and can carry diseases.

These viruses occur in overlapping regions, meaning co-infections are likely. Rosa noted that such situations increase the chance for viruses to exchange genetic material, though no recombinations between TSWV and INSV have been documented.

One possible reason, she explained, is that while thrips can acquire both viruses, they tend to transmit only one, often favoring INSV.

In the study, Rosa’s team infected Nicotiana benthamiana plants with single or mixed virus combinations, both simultaneously and at different times. They measured virus levels and used small RNA sequencing to assess how the plants processed each virus.

Results showed fewer co-infected plants than single-virus plants, with TSWV present at much lower levels in mixed infections. Small RNA analysis confirmed that INSV was processed similarly in both cases, while TSWV was processed differently.

“Basically, we have a much lower level of TSWV small RNAs in mixed infections compared to single infections,” Rosa said, highlighting the plant’s apparent preference for INSV.

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