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ABSTRACT: Melon necrotic spot virus (MNSV) is transmitted by the fungus Olpidium
bornovanus. In this study, we used immunofluorescence microscopy to detect MNSV particles over the entire surface of the O. bornovanus zoospore; MNSV particles were not detected on the related fungus O. virulentus, which cannot transmit MNSV. The amino acid substitution Ile → Phe at position 300 in the MNSV coat protein resulted in loss
of both specific binding and fungal transmission, while virion assembly and biological aspects were unaffected. Taken together,
these results suggest that the MNSV coat protein acts as a ligand to the O. bornovanus zoospore as part of a fungal-vector transmission system.
Journal of General Plant Pathology 04/2012; 74(2):176-181. · 0.69 Impact Factor
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ABSTRACT: The L11Y strain of Tomato mosaic virus (ToMV) causes severe chlorosis on infected tobacco leaves. Sequencing analysis for the genome showed that L11Y contained multiple nucleotide changes and that some led to amino acid substitutions, when compared with that of the common
L strain of ToMV. The chimeric virus, which has the CP of L11Y in the context of the L strain RNA genome, caused severe chlorosis on infected tobacco plants, suggesting that the CP of
L11Y containing three amino acid changes (E33S, A86T and E97K) was the determinant of the chlorosis. Two of these amino acid
changes (A86T and E97K) were associated with the induction of chlorosis when present together in the CP. Severe destruction
and deformation of chloroplasts and the formation of discrete dark-staining materials adjacent to chloroplasts were observed
with electron microscopy in L11Y-infected plants. Fewer virus particles accumulated in the cytoplasm of L11Y-infected plant cells. The level of accumulation of CP subgenomic RNA and CP in the infected protoplasts was similar between
L and L11Y. Fewer virus particles accumulated in L11Y-infected protoplasts, and many of them were shorter-than-full-length.
Journal of General Plant Pathology 04/2012; 75(4):297-306. · 0.69 Impact Factor
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ABSTRACT: The western flower thrips (Frankliniella occidentalis [Pergande]) is one of the most important insect herbivores of cultivated plants. However, no pesticide provides complete control of this species, and insecticide resistance has emerged around the world. We previously reported the important role of jasmonate (JA) in the plant's immediate response to thrips feeding by using an Arabidopsis leaf disc system. In this study, as the first step toward practical use of JA in thrips control, we analyzed the effect of JA-regulated Arabidopsis defense at the whole plant level on thrips behavior and life cycle at the population level over an extended period. We also studied the effectiveness of JA-regulated plant defense on thrips damage in Chinese cabbage (Brassica rapa subsp. pekinensis).
Thrips oviposited more on Arabidopsis JA-insensitive coi1-1 mutants than on WT plants, and the population density of the following thrips generation increased on coi1-1 mutants. Moreover, thrips preferred coi1-1 mutants more than WT plants. Application of JA to WT plants before thrips attack decreased the thrips population. To analyze these important functions of JA in a brassica crop plant, we analyzed the expression of marker genes for JA response in B. rapa. Thrips feeding induced expression of these marker genes and significantly increased the JA content in B. rapa. Application of JA to B. rapa enhanced plant resistance to thrips, restricted oviposition, and reduced the population density of the following generation.
Our results indicate that the JA-regulated plant defense restricts thrips performance and preference, and plays an important role in the resistance of Arabidopsis and B. rapa to thrips damage.
BMC Plant Biology 08/2009; 9:97. · 3.45 Impact Factor
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ABSTRACT: The virulence factor of Melon necrotic spot virus (MNSV), a virus that induces systemic necrotic spot disease on melon plants, was investigated. When the replication protein p29 was expressed in N. benthamiana using a Cucumber mosaic virus vector, necrotic spots appeared on the leaf tissue. Transmission electron microscopy revealed abnormal mitochondrial aggregation in these tissues. Fractionation of tissues expressing p29 and confocal imaging using GFP-tagged p29 revealed that p29 associated with the mitochondrial membrane as an integral membrane protein. Expression analysis of p29 deletion fragments and prediction of hydrophobic transmembrane domains (TMDs) in p29 showed that deletion of the second putative TMD from p29 led to deficiencies in both the mitochondrial localization and virulence of p29. Taken together, these results indicated that MNSV p29 interacts with the mitochondrial membrane and that p29 may be a virulence factor causing the observed necrosis.
Virology 07/2009; 390(2):239-49. · 3.35 Impact Factor
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ABSTRACT: We analyzed the interaction between Arabidopsis and western flower thrips (Frankliniella occidentalis), which are one of the most serious insect pests of cultivated plants. We focused on the function of the immunity-related plant hormones jasmonate (JA), ethylene (ET) and salicylic acid (SA) in the plant's response to thrip feeding. Expression of the marker genes for each hormone response was induced by thrip feeding in wild-type (WT) plants. Further analyses in the hormone-related mutants coi1-1 (JA insensitive), ein2-1 and ein3-1 (ET insensitive) and eds16-1 (SA deficient) suggested the importance of these hormones in the plant response to feeding. Comparative transcriptome analyses suggested a strong relationship between thrip feeding and JA treatment, but not ET or SA treatment. The JA content of WT plants was significantly increased after thrip feeding. Moreover, coi1-1, but not ein2-1, showed lower feeding tolerance against thrips than the WT. Application of JA to WT plants before thrip feeding enhanced the plants' feeding tolerance. JA modulates several defense responses in cooperation with ET, but application of the ET precursor 1-aminocyclopropane-carboxylic acid had a marked negative effect on feeding tolerance. Our results indicate that JA plays an important role in Arabidopsis in terms of response to, and tolerance against, thrip feeding.
Plant and Cell Physiology 02/2008; 49(1):68-80. · 4.70 Impact Factor
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ABSTRACT: ABSTRACT The Capsicum spp. L genes (L(1) to L(4)) confer resistance to tobamoviruses. Currently, the L(4) gene from Capsicum chacoense is the most effective resistance gene and has been used widely in breeding programs in Japan which have developed new resistant cultivars against Pepper mild mottle virus (PMMoV). However, in 2004, mild mosaic symptoms began appearing on the leaves of commercial pepper plants in the field which possessed the L(4) resistance gene. Serological and biological assays on Capsicum spp. identified the causal virus strain as a previously unreported pathotype, P(1,2,3,4). PMMoV sequence analysis of the virus and site-directed mutagenesis using a PMMoV-J of the P(1,2) pathotype revealed that two amino acid substitutions in the coat protein, Gln to Arg at position 46 and Gly to Lys at position 85, were responsible for overcoming the L(4) resistance gene.
Phytopathology 08/2007; 97(7):787-93. · 2.80 Impact Factor
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ABSTRACT: To clarify the mechanism of seed transmission of Pepper mild mottle virus (PMMoV), the virus was immunolocalized in Capsicum annuum seeds using fluorescence microscopy. Two distinct patterns were observed: In the first, PMMoV was present in the epidermis and parenchyma but not in the endosperm or embryo; in the second, the virus was restricted to the surface of the epidermis and parenchyma. These findings shed light on the fundamental mechanisms of seed transmission of tobamoviruses and may aid in the design of new methods to prevent the spread of seedborne virus diseases.
Journal of General Plant Pathology 05/2005; 71(3):238-242. · 0.69 Impact Factor
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ABSTRACT: ABSTRACT If acquisition access feeding (AAF) is first given after adult eclosion, none of the nine thrips species able to serve as tospovirus vectors can become infective. The previous cellular investigations of this phenomenon, carried out only in Frankliniella occidentalis, suggested that infectivity was prevented because the type member of the tospoviruses, Tomato spotted wilt virus (TSWV), was unable to enter the midgut of adult thrips. The present study extends a cellular view of tospovirus-thrips interactions to a species other than the western flower thrips, F. occidentalis. Our findings show that TSWV enters and replicates within the midgut of adult Thrips setosus, but does not infect cells beyond the midgut epithelia. After AAF as adult, TSWV replicated in T. setosus midgut cells as indicated by significant increases in nucleocapsid (N) protein detected by double-antibody sandwich enzyme-linked immunosorbent assay, and the presence of inclusions containing the S RNA-encoded nonstructural and N proteins revealed by microscopic observations. Electron microscopic observations of adult insects showed that no infection occurred in cells beyond the midgut epithelia, and insects subsampled from the same cohorts could not transmit TSWV. In contrast, electron microscopy observations of larval T. setosus revealed that TSWV infected the midgut and muscle cells, and adult insects developing from these cohorts had infected salivary glands and were able to transmit TSWV. Mature virions were observed only in the salivary glands of adults developing from infected larvae. Our findings suggest that the barrier to infectivity in T. setosus adults differs from that shown for F. occidentalis adults.
Phytopathology 01/2002; 91(12):1149-55. · 2.80 Impact Factor
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ABSTRACT: then declined drastically from the second-instar lar-Localization of tomato spotted wilt tospovirus in larvae and pupae of the val to pupal stage. During the adult stage after ecdysis, persistently low insect vector Thrips setosus. Phytopathology 86:1199-1203. N protein titers were demonstrated by DAS-ELISA, but adult thrips could transmit the virus. N protein was localized in first-and second-Changes in the accumulation of tomato spotted wilt tospovirus instar larvae and pupae by indirect immunofluorescence. On the second (TSWV) nucleocapsid (N) protein in Thrips setosus, an insect vector, to fourth days after acquisition, specific fluorescence signals were de-from eclosion to 17 days were revealed by the double-antibody sand-tected within the anterior midgut that then spread to the whole midgut wich-enzyme-linked immunosorbent assay (DAS-ELISA) system with during the second-instar larval stage. As time elapsed, N protein was individual thrips. First-instar larvae were fed on TSWV-infected Datura detected throughout the larval midgut and possibly within the salivary stramonium for 2 h, and then kept on healthy Vigna susquipedaris. Indi-glands in pupae at 6 days after acquisition. Fluorescence signals within viduals were subsampled for 17 days from first-instar larval to adult the pupal midgut were observed, but were not as intense as in larvae. stage. The N protein concentration increased gradually from the first-to second-instar larval stage after acquisition feeding, peaking on day 5. Additional keywords: detection, histochemistry.
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