Localization and subcellular association of Grapevine Pinot Gris Virus in grapevine leaf tissues

Abstract

Despite the increasing impact of Grapevine Pinot gris disease (GPG-disease) worldwide, etiology about this disorder is still uncertain. The presence of the putative causal agent, the Grapevine Pinot Gris Virus (GPGV), has been reported in symptomatic grapevines (presenting stunting, chlorotic mottling, and leaf deformation) as well as in symptom-free plants. Moreover, information on virus localization in grapevine tissues and virus-plant interactions at the cytological level is missing at all. Ultrastructural and cytochemical investigations were undertaken to detect virus particles and the associated cytopathic effects in field-grown grapevine showing different symptom severity. Asymptomatic greenhouse-grown grapevines, which tested negative for GPGV by real time RT-PCR, were sampled as controls. Multiplex real-time RT-PCR and ELISA tests excluded the presence of viruses included in the Italian certification program both in field-grown and greenhouse-grown grapevines. Conversely, evidence was found for ubiquitous presence of Grapevine Rupestris Stem Pitting-associated Virus (GRSPaV), Hop Stunt Viroid (HSVd), and Grapevine Yellow Speckle Viroid 1 (GYSVd-1) in both plant groups. Moreover, in every field-grown grapevine, GPGV was detected by real-time RT-PCR. Ultrastructural observations and immunogold labelling assays showed filamentous flexuous viruses in the bundle sheath cells, often located inside membrane-bound organelles. No cytological differences were observed among field-grown grapevine samples showing different symptom severity. GPGV localization and associated ultrastructural modifications are reported and discussed, in the perspective of assisting management and control of the disease.Electronic supplementary materialThe online version of this article (10.1007/s00709-017-1198-5) contains supplementary material, which is available to authorized users.

With or Without You: Altered Plant Response to Boron-Deficiency in Hydroponically Grown Grapevines Infected by Grapevine Pinot Gris Virus Suggests a Relation Between Grapevine Leaf Mottling and Deformation Symptom Occurrence and Boron Plant Availability

“…In fact, GPGV−/+B and GPGV+/+B plants displayed well-preserved root cells with normal histological and ultrastructural organization (Figures 2A-H, respectively). GPGV, detected in the BSCs of roots of GPGV+/+B plants, was not associated with any alteration besides membrane-bound organelle, described by Tarquini et al (2018) as putative endoplasmic reticulum (ER) rearrangement ( Figure 2F; Tarquini et al, 2018). In the case of B starvation, GPGV− root tissues displayed strong perturbation of both cortical and vascular regions ( Figure 2I).…”

“…Cuttings were obtained from dormant canes of grapevines (cv Pinot gris, clone VCR 5), collected in December 2017 from symptomatic and asymptomatic plants of a 12-yearold vineyard located in Farra d'Isonzo (Gorizia Province, Italy;45.91676765918134 N, 13.530162621173078 E). The eventual occurrence of the main grapevine viruses (Giampetruzzi et al, 2012;Saldarelli et al, 2015;Bertazzon et al, 2017;Gentili et al, 2017;Morán et al, 2018;Tarquini et al, 2018;Marra et al, 2019;Tarquini et al, 2019a,b) was checked as described in Tarquini et al (2018) and Tarquini et al (2019a). The presence of viruses included in the Italian certification program (Bertazzon et al, 2002) was excluded, while the detection of viruses and viroids reported in Pinot gris tissues simultaneously with GPGV (Giampetruzzi et al, 2012 andSaldarelli et al, 2015, i.e.…”

“…For root observations, plants were carefully removed from the pots, nutrient solution was washed from the roots and a 5 mmlong portion of the fine roots corresponding to the secondary growth area (Gambetta et al, 2013) were cut, fixed in 3% glutaraldehyde and processed as described in Tarquini et al (2018). Leaf segments (3-4 mm in length) including both vein tissues and surrounding parenchyma cells were fixed in 3% glutaraldehyde and processed in the same manner.…”

“…GPGV is a positive-sense single-stranded RNA-virus belonging to the Betaflexiviridae virus family, genus Trichovirus (Martelli, 2014). It is localized in the bundle sheath cells (BSCs) of the phloem parenchyma (Tarquini et al, 2018) and it is probably spread by the feeding activity of the grapevine eriophyoid mite Colomerus vitis (Malagnini et al, 2016).…”

“…The association between the symptomatology and the presence of the virus is unclear, with several reports documenting a great number of symptomless grapevines hosting GPGV (Giampetruzzi et al, 2012;Saldarelli et al, 2013Saldarelli et al, , 2015Forte et al, 2014;Mavrič Pleško et al, 2014;Bianchi et al, 2015). Furthermore, transmission electron microscopy (TEM) investigations performed on infected tissues of field-grown grapevines have not revealed any differences in ultrastructural cytopathy induced by GPGV in symptomatic or asymptomatic plants (Tarquini et al, 2018).…”