Abiotic stress responses promote Potato virus A infection in Nicotiana benthamiana

Authors

  • TAINA SUNTIO,

    1. Department of Food and Environmental Sciences, P.O. Box 27, 00014 University of Helsinki, Helsinki, Finland
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    • Current address: Department of Biosciences, PO Box 56, 00014 University of Helsinki, Helsinki, Finland.

  • KRISTIINA MÄKINEN

    Corresponding author
    1. Department of Food and Environmental Sciences, P.O. Box 27, 00014 University of Helsinki, Helsinki, Finland
      : Email: kristiina.makinen@helsinki.fi
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: Email: kristiina.makinen@helsinki.fi

SUMMARY

The effect of abiotic stress responses on Potato virus A (PVA; genus Potyvirus) infection was studied. Salt, osmotic and wounding stress all increased PVA gene expression in infected Nicotiana benthamiana leaves. According to the literature, an early response to these stresses is an elevation in cytosolic Ca2+ concentration. The infiltration of 0.1 m CaCl2 into the infected leaf area enhanced the translation of PVA RNA, and this Ca2+-induced effect was more profound than that induced solely by osmotic stress. The inhibition of voltage-gated Ca2+ channels within the plasma membrane abolished the Ca2+ effect, suggesting that Ca2+ had to be transported into the cytosol to affect viral gene expression. This was also supported by a reduced wounding effect in the presence of the Ca2+-chelating agent ethylene glycol tetraacetic acid (EGTA). In the absence of viral replication, the intense synthesis of viral proteins in response to Ca2+ was transient. However, a Ca2+ pulse administered at the onset of wild-type PVA infection enhanced the progress of infection within the locally infected leaf, and the virus appeared earlier in the systemic leaves than in the control plants. This suggests that the cellular environment was thoroughly modified by the Ca2+ pulse to support viral infection. One message of this study is that the sensing of abiotic stress, which leads to cellular responses, probably via Ca2+ signalling, associated with enhanced virus infection, may lead to higher field crop losses. Therefore, the effect of abiotic stress on plant viral infection warrants further analysis.

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