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Background <p><i>Paulownia</i> witches’ broom disease (PaWB), caused by phytoplasmas, results in economic losses. Thymidine kinase (TDK) is a key enzyme in the deoxythymidine triphosphate‌ (dTTP) synthesis pathway of phytoplasma, and dTTP serves as an essential precursor for DNA replication during cell proliferation, but its role in regulating phytoplasma proliferation and virulence remains unclear.</p> Results <p>To characterize the role of TDK in phytoplasma proliferation and virulence, in this study, two PaWB phytoplasma <i>tdk</i> genotypes were identified via sampling in China, and <i>tdk-1</i> was the most widely distributed. Phylogenetic analysis revealed that single-copied <i>tdk</i> exhibited higher phylogenetic resolution than 16S rRNA for phytoplasma molecular classification. In silico prediction showed that TDK functions as a thymidine kinase in these phytoplasmas. Furthermore, TDK protein expression was detected in PaWB-infected tissues. Immunofluorescence microscopy showed that TDK co-localized with phytoplasmas in sieve tube elements. Immunoelectron microscopy showed that TDK mainly localized in dividing phytoplasma cells. Absolute quantitative analysis revealed that <i>tdk</i> mRNA expression was positively associated with phytoplasma proliferation. Overexpressing <i>tdk</i> in <i>Pseudomonas syringae</i> pv. <i>tomato</i> (<i>Pst</i>) DC3000 significantly enhanced bacterial growth and increased its virulence in <i>Arabidopsis</i>.</p> Conclusions <p>Overall, these results identify phytoplasma TDK as a critical proliferation-associated pathogenicity factor that promotes pathogen proliferation, providing a potential molecular target for controlling PaWB.</p>

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Genetic variation and proliferation-promoting virulence function of thymidine kinase from Paulownia witches’ broom phytoplasma

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月10日

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  • Chuansheng Song,
  • Dezhi Kong,
  • Xia Li,
  • Jungang Wang,
  • You Lv,
  • Gaofeng Liu,
  • Lihong Dong,
  • Xiaofei Kang,
  • Xiaofei Li,
  • Keyu Guo,
  • Caili Lin,
  • Cuiping Wan

摘要

Background

Paulownia witches’ broom disease (PaWB), caused by phytoplasmas, results in economic losses. Thymidine kinase (TDK) is a key enzyme in the deoxythymidine triphosphate‌ (dTTP) synthesis pathway of phytoplasma, and dTTP serves as an essential precursor for DNA replication during cell proliferation, but its role in regulating phytoplasma proliferation and virulence remains unclear.

Results

To characterize the role of TDK in phytoplasma proliferation and virulence, in this study, two PaWB phytoplasma tdk genotypes were identified via sampling in China, and tdk-1 was the most widely distributed. Phylogenetic analysis revealed that single-copied tdk exhibited higher phylogenetic resolution than 16S rRNA for phytoplasma molecular classification. In silico prediction showed that TDK functions as a thymidine kinase in these phytoplasmas. Furthermore, TDK protein expression was detected in PaWB-infected tissues. Immunofluorescence microscopy showed that TDK co-localized with phytoplasmas in sieve tube elements. Immunoelectron microscopy showed that TDK mainly localized in dividing phytoplasma cells. Absolute quantitative analysis revealed that tdk mRNA expression was positively associated with phytoplasma proliferation. Overexpressing tdk in Pseudomonas syringae pv. tomato (Pst) DC3000 significantly enhanced bacterial growth and increased its virulence in Arabidopsis.

Conclusions

Overall, these results identify phytoplasma TDK as a critical proliferation-associated pathogenicity factor that promotes pathogen proliferation, providing a potential molecular target for controlling PaWB.