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The immune response of hemocytes of the insect Oncopeltus fasciatus against the flagellate Phytomonas serpens.

Alves e Silva TL, Vasconcellos LR, Lopes AH, Souto-Padrón T - PLoS ONE (2013)

Bottom Line: The parasites reached the O. fasciatus salivary glands at least six hours post-infection.After 72 hours post-infection, many parasites were attached to the salivary gland outer surface.Thus, the cellular responses did not kill all the parasites.

View Article: PubMed Central - PubMed

Affiliation: Instituto de Microbiologia Paulo de Góes, Centro de Ciências da Saúde, Bloco I, Universidade Federal do Rio de Janeiro, Ilha do Fundão, Rio de Janeiro, Brazil.

ABSTRACT
The genus Phytomonas includes parasites that are etiological agents of important plant diseases, especially in Central and South America. These parasites are transmitted to plants via the bite of an infected phytophagous hemipteran. Despite the economic impact of these parasites, many basic questions regarding the genus Phytomonas remain unanswered, such as the mechanism by which the parasites cope with the immune response of the insect vector. In this report, using a model of systemic infection, we describe the function of Oncopeltus fasciatus hemocytes in the immune response towards the tomato parasite Phytomonas serpens. Hemocytes respond to infection by trapping parasites in nodular structures and phagocytizing the parasites. In electron microscopy of hemocytes, parasites were located inside vacuoles, which appear fused with lysosomes. The parasites reached the O. fasciatus salivary glands at least six hours post-infection. After 72 hours post-infection, many parasites were attached to the salivary gland outer surface. Thus, the cellular responses did not kill all the parasites.

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Intracellular fate of P.serpens.Infected hemocytes were analyzed at 6 hpi. (A) Parasites were observed in a tight PV, for which the membrane is indicated by the black arrows; (B) parasites were also observed in larger PV (asterisk) filled with the same structures (myelin figures, electron-dense matrix and lipid inclusions) regularly found in the lysosomes (L) of hemocytes; (C) lysosomes previously labeled with the BSA-gold complex (10 nm) were observed around the PV (black arrows). (D) In some sections, it was possible to observe gold particles inside the PV and close to the parasite (black arrow in C). L, lysosomes; P, parasite; F, flagellum. Scale bars: (A, C and D) 1 µm, (B) 200 nm.
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pone-0072076-g007: Intracellular fate of P.serpens.Infected hemocytes were analyzed at 6 hpi. (A) Parasites were observed in a tight PV, for which the membrane is indicated by the black arrows; (B) parasites were also observed in larger PV (asterisk) filled with the same structures (myelin figures, electron-dense matrix and lipid inclusions) regularly found in the lysosomes (L) of hemocytes; (C) lysosomes previously labeled with the BSA-gold complex (10 nm) were observed around the PV (black arrows). (D) In some sections, it was possible to observe gold particles inside the PV and close to the parasite (black arrow in C). L, lysosomes; P, parasite; F, flagellum. Scale bars: (A, C and D) 1 µm, (B) 200 nm.

Mentions: To identify the precise localization of internalized parasites inside hemocytes, we followed the internalization process using transmission electron microscopy (Fig. 7). After 2 hpi, parasites were observed inside a vacuole resembling parasitophorous vacuoles (PV) of other systems. These vacuoles were identified due to the presence of a continuous membrane around the parasite; we usually found only one parasite per vacuole (Fig. 7A). After 6 h, lysosome-like organelles, which are characterized by the presence of multiple vesicles and concentric membranes resembling myelin figures immersed in an electron-dense matrix, fused with the PV. (Fig. 7B and 7C). To confirm the lysosomal characteristics of some compartments, we pre-incubated hemocytes with gold-labeled BSA. Different cytoplasmic compartments were labeled (Fig. 7C and 7D). At 72 hpi, the parasites remained located within the PV. However, we observed a greater number of parasites per PV, thereby suggesting that they not only survive within the PV, but they could also be able to multiply there (Fig. 8A and 8B).


The immune response of hemocytes of the insect Oncopeltus fasciatus against the flagellate Phytomonas serpens.

Alves e Silva TL, Vasconcellos LR, Lopes AH, Souto-Padrón T - PLoS ONE (2013)

Intracellular fate of P.serpens.Infected hemocytes were analyzed at 6 hpi. (A) Parasites were observed in a tight PV, for which the membrane is indicated by the black arrows; (B) parasites were also observed in larger PV (asterisk) filled with the same structures (myelin figures, electron-dense matrix and lipid inclusions) regularly found in the lysosomes (L) of hemocytes; (C) lysosomes previously labeled with the BSA-gold complex (10 nm) were observed around the PV (black arrows). (D) In some sections, it was possible to observe gold particles inside the PV and close to the parasite (black arrow in C). L, lysosomes; P, parasite; F, flagellum. Scale bars: (A, C and D) 1 µm, (B) 200 nm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3756046&req=5

pone-0072076-g007: Intracellular fate of P.serpens.Infected hemocytes were analyzed at 6 hpi. (A) Parasites were observed in a tight PV, for which the membrane is indicated by the black arrows; (B) parasites were also observed in larger PV (asterisk) filled with the same structures (myelin figures, electron-dense matrix and lipid inclusions) regularly found in the lysosomes (L) of hemocytes; (C) lysosomes previously labeled with the BSA-gold complex (10 nm) were observed around the PV (black arrows). (D) In some sections, it was possible to observe gold particles inside the PV and close to the parasite (black arrow in C). L, lysosomes; P, parasite; F, flagellum. Scale bars: (A, C and D) 1 µm, (B) 200 nm.
Mentions: To identify the precise localization of internalized parasites inside hemocytes, we followed the internalization process using transmission electron microscopy (Fig. 7). After 2 hpi, parasites were observed inside a vacuole resembling parasitophorous vacuoles (PV) of other systems. These vacuoles were identified due to the presence of a continuous membrane around the parasite; we usually found only one parasite per vacuole (Fig. 7A). After 6 h, lysosome-like organelles, which are characterized by the presence of multiple vesicles and concentric membranes resembling myelin figures immersed in an electron-dense matrix, fused with the PV. (Fig. 7B and 7C). To confirm the lysosomal characteristics of some compartments, we pre-incubated hemocytes with gold-labeled BSA. Different cytoplasmic compartments were labeled (Fig. 7C and 7D). At 72 hpi, the parasites remained located within the PV. However, we observed a greater number of parasites per PV, thereby suggesting that they not only survive within the PV, but they could also be able to multiply there (Fig. 8A and 8B).

Bottom Line: The parasites reached the O. fasciatus salivary glands at least six hours post-infection.After 72 hours post-infection, many parasites were attached to the salivary gland outer surface.Thus, the cellular responses did not kill all the parasites.

View Article: PubMed Central - PubMed

Affiliation: Instituto de Microbiologia Paulo de Góes, Centro de Ciências da Saúde, Bloco I, Universidade Federal do Rio de Janeiro, Ilha do Fundão, Rio de Janeiro, Brazil.

ABSTRACT
The genus Phytomonas includes parasites that are etiological agents of important plant diseases, especially in Central and South America. These parasites are transmitted to plants via the bite of an infected phytophagous hemipteran. Despite the economic impact of these parasites, many basic questions regarding the genus Phytomonas remain unanswered, such as the mechanism by which the parasites cope with the immune response of the insect vector. In this report, using a model of systemic infection, we describe the function of Oncopeltus fasciatus hemocytes in the immune response towards the tomato parasite Phytomonas serpens. Hemocytes respond to infection by trapping parasites in nodular structures and phagocytizing the parasites. In electron microscopy of hemocytes, parasites were located inside vacuoles, which appear fused with lysosomes. The parasites reached the O. fasciatus salivary glands at least six hours post-infection. After 72 hours post-infection, many parasites were attached to the salivary gland outer surface. Thus, the cellular responses did not kill all the parasites.

Show MeSH
Related in: MedlinePlus