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

Buxa SV, Degola F, Polizzotto R, De Marco F, Loschi A, Kogel KH, di Toppi LS, van Bel AJ, Musetti R - Front Plant Sci (2015)

Bottom Line: We investigated modifications of the sieve-element ultrastructure induced in tomato plants by 'Candidatus Phytoplasma solani,' the pathogen associated with the stolbur disease.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Phytopathology and Applied Zoology, Justus Liebig University Giessen, Germany.

ABSTRACT
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.

No MeSH data available.


Related in: MedlinePlus

(A–D) Western blot analyses of S. lycopersicum midrib extracts. Three healthy (lanes 1–3) and three infected (lanes 4–6) plants were analyzed. Immunoreactive signals corresponding to actin and ER luminal binding protein (BiP) displayed the expected molecular weights of ≈40 and ≈78 kDa, respectively (A). Amount of loaded protein were checked by Ponceau-S staining (B). Quantification of immunoreactive luminescence signals was achieved by densitometric scanning of the respective actin (C) and BiP (D) bands. The mean of six replicates (±SD) was calculated for each sample. Actin T-value: –9.977; BiP T-value: 15.068. * denotes significant difference of the means (P-values ≤ 0.001).
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Figure 6: (A–D) Western blot analyses of S. lycopersicum midrib extracts. Three healthy (lanes 1–3) and three infected (lanes 4–6) plants were analyzed. Immunoreactive signals corresponding to actin and ER luminal binding protein (BiP) displayed the expected molecular weights of ≈40 and ≈78 kDa, respectively (A). Amount of loaded protein were checked by Ponceau-S staining (B). Quantification of immunoreactive luminescence signals was achieved by densitometric scanning of the respective actin (C) and BiP (D) bands. The mean of six replicates (±SD) was calculated for each sample. Actin T-value: –9.977; BiP T-value: 15.068. * denotes significant difference of the means (P-values ≤ 0.001).

Mentions: Western Blot analyses (Figures 6A–D) were performed on midrib extracts from healthy and stolbur-diseased plants. The rationale of using midribs is that they contain the sieve elements as the phytoplasma carriers. This approach revealed that actin and BiP protein levels significantly varied in infected plants compared to the healthy ones (Figure 6A). Densitometric analyses indicated that the actin level in extracts from infected midribs was significantly lower than in healthy ones (Figure 6C). The 40% decrease (Figure 6C) is in agreement with the decreased actin contents measured by immuno-gold labeling (Table 2). By contrast, infected tissues displayed a 6.3-fold-increased BiP protein level in comparison with healthy samples (Figure 6D). The densitometric differences in protein expression of both actin and BiP in healthy and infected plants turned out to be highly significant (p-value ≤ 0.001).


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

Buxa SV, Degola F, Polizzotto R, De Marco F, Loschi A, Kogel KH, di Toppi LS, van Bel AJ, Musetti R - Front Plant Sci (2015)

(A–D) Western blot analyses of S. lycopersicum midrib extracts. Three healthy (lanes 1–3) and three infected (lanes 4–6) plants were analyzed. Immunoreactive signals corresponding to actin and ER luminal binding protein (BiP) displayed the expected molecular weights of ≈40 and ≈78 kDa, respectively (A). Amount of loaded protein were checked by Ponceau-S staining (B). Quantification of immunoreactive luminescence signals was achieved by densitometric scanning of the respective actin (C) and BiP (D) bands. The mean of six replicates (±SD) was calculated for each sample. Actin T-value: –9.977; BiP T-value: 15.068. * denotes significant difference of the means (P-values ≤ 0.001).
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4541602&req=5

Figure 6: (A–D) Western blot analyses of S. lycopersicum midrib extracts. Three healthy (lanes 1–3) and three infected (lanes 4–6) plants were analyzed. Immunoreactive signals corresponding to actin and ER luminal binding protein (BiP) displayed the expected molecular weights of ≈40 and ≈78 kDa, respectively (A). Amount of loaded protein were checked by Ponceau-S staining (B). Quantification of immunoreactive luminescence signals was achieved by densitometric scanning of the respective actin (C) and BiP (D) bands. The mean of six replicates (±SD) was calculated for each sample. Actin T-value: –9.977; BiP T-value: 15.068. * denotes significant difference of the means (P-values ≤ 0.001).
Mentions: Western Blot analyses (Figures 6A–D) were performed on midrib extracts from healthy and stolbur-diseased plants. The rationale of using midribs is that they contain the sieve elements as the phytoplasma carriers. This approach revealed that actin and BiP protein levels significantly varied in infected plants compared to the healthy ones (Figure 6A). Densitometric analyses indicated that the actin level in extracts from infected midribs was significantly lower than in healthy ones (Figure 6C). The 40% decrease (Figure 6C) is in agreement with the decreased actin contents measured by immuno-gold labeling (Table 2). By contrast, infected tissues displayed a 6.3-fold-increased BiP protein level in comparison with healthy samples (Figure 6D). The densitometric differences in protein expression of both actin and BiP in healthy and infected plants turned out to be highly significant (p-value ≤ 0.001).

Bottom Line: We investigated modifications of the sieve-element ultrastructure induced in tomato plants by 'Candidatus Phytoplasma solani,' the pathogen associated with the stolbur disease.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Phytopathology and Applied Zoology, Justus Liebig University Giessen, Germany.

ABSTRACT
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.

No MeSH data available.


Related in: MedlinePlus