Depuration Capacity of Mussels (Mytilus galloprovincialis) in Presence of Marteilia Spp. Parasites

Bivalve molluscs are filter-feeding organisms present in the water column: during their activity, they could retain micro-organisms that are potentially dangerous to human health. For this reason, EU Regulations may require that a purification treatment be performed prior to bivalve trade. The length of the purification process could be affected by stress factors, such as parasitic infections. The purpose of this study was to determine if the presence of Marteilia spp. parasite in shellfish could modify time and efficacy of their microbiological purification treatment, in order to set up specific protocols. Lysosomal membrane stability, phagocytosis capacity, granulocyte/hyalinocyte rate and neutral lipid accumulation are biomarkers used to evaluate shellfish physiological state. These biomarkers were used to exclude any differences caused by stressor factors that could affect the purification results. Mussels were sampled from two different production areas. The presence or absence of parasites was confirmed by cytological test. Both groups of parasitized and non-parasitized mussels were contaminated with E.coli: they were then sampled for microbiological analyses and tested for biomarkers for up to 70 hours of purification. Parasitized and non-parasitized molluscs did not show any differences in levels of E. coli after 12, 24, 36, 48 and 70 hours of depuration. In relation to biomarkers, mussels seem to react to Lysosomal membrane stability in presence of Marteilia. The present study shows that the presence of Marteilia spp. does not affect the purification rate of mussels

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

Despite the increasing spread of Grapevine Leaf Mottling and Deformation (GLMD) worldwide, little is known about its etiology. After identification of grapevine Pinot gris virus (GPGV) as the presumptive causal agent of the disease in 2015, various publications have evaluated GPGV involvement in GLMD. Nevertheless, there are only partial clues to explain the presence of GPGV in both symptomatic and asymptomatic grapevines and the mechanisms that trigger symptom development, and so a consideration of new factors is required. Given the similarities between GLMD and boron (B)-deficiency symptoms in grapevine plants, we posited that GPGV interferes in B homeostasis. By using a hydroponic system to control B availability, we investigated the effects of different B supplies on grapevine phenotype and those of GPGV infection on B acquisition and translocation machinery, by means of microscopy, ionomic and gene expression analyses in both roots and leaves. The transcription of the genes regulating B homeostasis was unaffected by the presence of GPGV alone, but was severely altered in plants exposed to both GPGV infection and B-deficiency, allowing us to speculate that the capricious and patchy occurrence of GLMD symptoms in the field may not be related solely to GPGV, but to GPGV interference in plant responses to different B availabilities. This hypothesis found preliminary positive confirmations in analyses on field-grown plants

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

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. \ua9 2017 The Author(s

Filamentous sieve element proteins are able to limit phloem mass flow, but not phytoplasma spread

In Fabaceae, dispersion of forisomes\u2014highly ordered aggregates of sieve element proteins\u2014in response to phytoplasma infection was proposed to limit phloem mass flow and, hence, prevent pathogen spread. In this study, the involvement of filamentous sieve element proteins in the containment of phytoplasmas was investigated in non-Fabaceae plants. Healthy and infected Arabidopsis plants lacking one or two genes related to sieve element filament formation\u2014AtSEOR1 (At3g01680), AtSEOR2 (At3g01670), and AtPP2-A1 (At4g19840)\u2014were analysed. TEM images revealed that phytoplasma infection induces phloem protein filament formation in both the wild-type and mutant lines. This result suggests that, in contrast to previous hypotheses, sieve element filaments can be produced independently of AtSEOR1 and AtSEOR2 genes. Filament presence was accompanied by a compensatory overexpression of sieve element protein genes in infected mutant lines in comparison with wild-type lines. No correlation was found between phloem mass flow limitation and phytoplasma titre, which suggests that sieve element proteins are involved in defence mechanisms other than mechanical limitation of the pathogen

Phytoplasma infection in tomato is associated with re-organization of plasma membrane, ER stacks, and actin filaments in sieve elements

Phytoplasmas, biotrophic wall-less prokaryotes, only reside in sieve elements of their host plants. The essentials of the intimate interaction between phytoplasmas and their hosts are poorly understood, which calls for research on potential ultrastructural modifications. We investigated modifications of the sieve-element ultrastructure induced in tomato plants by ‘Candidatus Phytoplasma solani’, the pathogen associated with the stolbur disease. Phytoplasma infection induces a drastic re-organization of sieve-element substructures including changes in plasma membrane surface and distortion of the sieve-element reticulum. Observations of healthy and stolbur-diseased plants provided evidence for the emergence of structural links between sieve-element plasma membrane and phytoplasmas. One-sided actin aggregates on the phytoplasma surface also inferred a connection between phytoplasma and sieve-element cytoskeleton. Actin filaments displaced from the sieve-element mictoplasm to the surface of the phytoplasmas in infected sieve elements. Expression analysis revealed a decrease of actin and an increase of ER-resident chaperone luminal binding protein (BiP) in midribs of phytoplasma-infected plants. Collectively, the studies provided novel insights into ultrastructural responses of host sieve elements to phloem-restricted prokaryotes

Phytoplasma infection in tomato is associated with re-organization of plasma membrane, ER stacks, and actin filaments in sieve elements

Phytoplasmas, biotrophic wall-less prokaryotes, only reside in sieve elements of their host plants. The essentials of the intimate interaction between phytoplasmas and their hosts are poorly understood, which calls for research on potential ultrastructural modifications. We investigated modifications of the sieve-element ultrastructure induced in tomato plants by ‘Candidatus Phytoplasma solani,’ the pathogen associated with the stolbur disease. Phytoplasma infection induces a drastic re-organization of sieve-element substructures including changes in plasma membrane surface and distortion of the sieve-element reticulum. Observations of healthy and stolbur-diseased plants provided evidence for the emergence of structural links between sieve-element plasma membrane and phytoplasmas. One-sided actin aggregates on the phytoplasma surface also inferred a connection between phytoplasma and sieve-element cytoskeleton. Actin filaments displaced from the sieve-element mictoplasm to the surface of the phytoplasmas in infected sieve elements. Western blot analysis revealed a decrease of actin and an increase of ER-resident chaperone luminal binding protein (BiP) in midribs of phytoplasma-infected plants. Collectively, the studies provided novel insights into ultrastructural responses of host sieve elements to phloem-restricted prokaryotes

Looking inside phytoplasma-infected sieve elements: A combined microscopy approach using Arabidopsis thaliana as a model plant

Phytoplasmas are phloem-inhabiting plant pathogens that affect over one thousand plant species, representing a severe threat to agriculture. The absence of an effective curative strategy and the economic importance of many affected crops make a priority of studying how plants respond to phytoplasma infection. Nevertheless, the study of phytoplasmas has been hindered by the extreme difficulty of culturing them in vitro and by impediments to natural host plant surveys such as low phytoplasma titre, long plant life cycle and poor knowledge of natural host-plant biology. Stating correspondence between macroscopic symptoms of phytoplasma infected Arabidopsis thaliana and those observed in natural host plants, over the last decade some authors have started to use this plant as a model for studying phytoplasma-plant interactions. Nevertheless, the morphological and ultrastructural modifications occurring in A. thaliana tissues following phytoplasma infection have never been described in detail. In this work, we adopted a combined-microscopy approach to verify if A. thaliana can be considered a reliable model for the study of phytoplasma-plant interactions at the microscopical level. The consistent presence of phytoplasma in infected phloem allowed detailed study of the infection process and the relationship established by phytoplasmas with different components of the sieve elements. In infected A. thaliana, phytoplasmas induced strong disturbances of host plant development that were mainly due to phloem disorganization and impairment. Light microscopy showed collapse, necrosis and hyperplasia of phloem cells. TEM observations of sieve elements identified two common plant-responses to phytoplasma infection: phloem protein agglutination and callose deposition