The influence of cis‐acting P1 protein and translational elements on the expression of Potato virus Y helper‐component proteinase (HCPro) in heterologous systems and its suppression of silencing activity. (3rd March 2013)

• Record Type: Journal Article
• Authors: Tena Fernández, Fátima; González, Inmaculada; Doblas, Paula; Rodríguez, César; Sahana, Nandita; Kaur, Harpreet; Tenllado, Francisco; Praveen, Shelly; Canto, Tomas
• Is Part Of: Molecular plant pathology. Volume 14:Number 5(2013:Jun.)
• Page Start: 530
• Page End: 541
• Publication Date: 2013-03-03
• Subjects: Plant diseases -- Molecular aspects -- Periodicals; Plant-pathogen relationships -- Molecular aspects -- Periodicals; 571.936
• DOI: 10.1111/mpp.12025
• Languages: English
• ISSNs: 1464-6722

Abstract

<abstract abstract-type="main"> <title>Summary</title> <p>In the <italic>Potyvirus</italic> genus, the P1 protein is the first N‐terminal product processed from the viral polyprotein, followed by the helper‐component proteinase (HCPro). In silencing suppression patch assays, we found that <italic>Potato virus Y</italic> (PVY) HCPro expressed from a <italic>P1‐HCPro</italic> sequence increased the accumulation of a reporter gene, whereas protein expressed from an <italic>HCPro</italic> sequence did not, even with P1 supplied <italic>in trans</italic>. This enhancing effect of P1 has been noted in other potyviruses, but has remained unexplained. We analysed the accumulation of PVY HCPro in infiltrated tissues and found that it was higher when expressed from <italic>P1‐HCPro</italic> than from <italic>HCPro</italic> sequences. Co‐expression of heterologous suppressors increased the steady‐state level of mRNA expressed from the <italic>HCPro</italic> sequence, but not that of protein. This suggests that, in the absence of P1 upstream, either HCPro acquires a conformation that affects negatively its activity or stability, or that its translation is reduced. To test these options, we purified HCPro expressed in the presence or absence of upstream P1, and found no difference in purification pattern and final soluble state. By contrast, alteration of the Kozak context in the <italic>HCPro</italic> mRNA sequence to favour translation increased partially suppressor accumulation and activity. Furthermore, protein activity was not lower than in protein expressed from <italic>P1‐HCPro</italic> sequences. Thus, a direct role for P1 on HCPro suppressor activity or stability, by influencing its conformation during translation, can be excluded. However, P1 could still have an indirect effect favouring HCPro accumulation. Our data highlight the relevance of <italic>cis</italic>‐acting translational elements in the heterologous expression of HCPro.</p> </abstract>