Viral Protein Steers Host Range of Tomato Leaf Curl New Delhi Virus Strains

Tomato leaf curl New Delhi virus (ToLCNDV), a bipartite begomovirus, causes major losses in solanaceous and cucurbit crops, and new research identifies the nuclear shuttle protein as a key viral factor deciding which plants particular strains can infect. The study, published in BMC Plant Biology, compared two strains with different host ranges to pinpoint the molecular determinants of host specificity.

Viral strains differ in the hosts they can colonize: some infect both tomato and cucurbits, whereas others are restricted to cucurbits. Which viral components underlie these differences had remained unclear. To address the question, the researchers built agroinfectious clones of the cucurbit-restricted ToLCNDV-CB strain and the ToLCNDV-Jessore strain, which infects both tomato and cucurbits, and exchanged their genomic components.

Begomoviruses carry two genomic components, DNA-A and DNA-B. When the CB DNA-A component was tested in tomato, it established infection only when paired with the Jessore DNA-B component. This result demonstrated that DNA-B, rather than DNA-A, determines host specificity in this pairing of strains.

To narrow the determinant further, the team transiently expressed the nuclear shuttle protein (NSP), which is encoded by the Jessore DNA-B component. This single viral protein enabled the otherwise restricted CB DNA-A plus DNA-B combination to move systemically through tomato plants, identifying NSP as a key host-range determinant for the two tested strains.

The experiments also separated host specificity from virulence. The CB strain caused stronger symptoms in cucumber than the Jessore strain, and when CB DNA-A was combined with Jessore DNA-B in tomato, it enhanced disease severity. These findings indicate that DNA-A acts as a determinant of virulence, even though it does not control which host species is infected.

In a further test of how mixed infections shape host adaptation, the researchers co-inoculated tomato with the CB DNA-A plus DNA-B combination and two monopartite geminiviruses. Tomato yellow leaf curl Sardinia virus (TYLCSV) facilitated proliferation and systemic movement of the ToLCNDV-CB DNA-B component in tomato, showing that a helper effect from another virus can extend the range of a viral component. However, CB DNA-A was not detected in these co-infected plants, so the full bipartite virus did not establish.

The authors conclude that the NSP is a key viral factor determining host specificity in the two tested ToLCNDV strains, that DNA-A contributes to virulence, and that co-infection with other viruses can influence host adaptation. Because the study used agroinfectious clones and transient expression under controlled conditions, the findings apply to the strains and experimental systems tested rather than representing a survey of all ToLCNDV diversity in the field.

The work offers practical value for predicting viral epidemics, designing disease management strategies, and breeding resistant cultivars.

Subject of Research: Viral determinants of host range and virulence in tomato leaf curl New Delhi virus strains

Article Title: The nuclear shuttle protein is a key determinant of the ability of selected tomato leaf curl New Delhi virus strains to infect tomato plants

Article References: Zois, R., Veenendaal, L. D. H., van Damme, M., Möller, S. R., Maruthi, M. N., Bai, Y., & Wolters, A.-M. A. (2026). The nuclear shuttle protein is a key determinant of the ability of selected tomato leaf curl New Delhi virus strains to infect tomato plants. BMC Plant Biology. https://doi.org/10.1186/s12870-026-10277-3

Image Credits: AI Generated

DOI: 10.1186/s12870-026-10277-3

Keywords: ToLCNDV, begomovirus, nuclear shuttle protein, host range, tomato, cucurbits, DNA-A, DNA-B, TYLCSV, co-infection, virulence, plant virology