Biomedical subjects

E W Kitajima

Publications and source records attributed to E W Kitajima.

At least 19 recordsLinked to original sources

PubMed2004

A novel melon flexivirus transmitted by whitefly.

In recent years, a viral disease on melon plants has become a serious problem in Brazil. Symptoms were principally yellowing and mottling on older leaves. Long filamentous virus particles, resembling those of carlaviruses, were seen in symptomatic leaves. In this study, the 3' terminal region of the virus genome isolated from an infected plant, including the last two ORFs, was cloned and sequenced. The sequence comprised a polyadenilated tail and two ORFs, one exhibiting similarity to potexvirus and carlavirus coat protein gene and the second to a carlavirus protein with potential nucleic acid-binding property. The sequence analysis, the genome organization and the particle morphology indicated that the virus could be classified as a novel whitefly-transmitted flexivirus. The name Melon yellowing-associated virus (MYaV) is tentatively suggested for this virus.

Amino Acid Sequence↗

PubMed2003

Brevipalpus-transmitted plant virus and virus-like diseases: cytopathology and some recent cases.

An increasing number of diseases transmitted by Brevipalpus mite species (Acari: Tenuipalpidae) is being identified that affect economically important plants such as citrus, coffee, passion fruit, orchids, and several ornamentals. All of these diseases are characterized by localized lesions (chlorotic, green spots, or ringspots) on leaves, stems, and fruits. Virus or virus-like agents are considered to be the causal agents, possibly transmitted in a circulative-propagative manner by Brevipalpus mites. The virus or virus-like particles are short, rod-like, or bacilliform, that induce two characteristic types of cell alteration: (1) 'Nuclear type'--nuclei of parenchyma and epidermal cells in the lesions often contain a large electron lucent inclusion. Short, naked, rod-like (40-50 nm x 100-110 nm) particles may be seen in the viroplasm or nucleoplasm and in the cytoplasm. These particles are commonly arranged perpendicularly on the membranes of the nuclear envelope or endoplasmic reticulum (ER). In a very few instances, they were found to be membrane-bound, within the ER cavities. (2) 'Cytoplasmic type'--short bacilliform particles (60-70 nm x 110-120 nm) are present within the cisternae of the ER and often have electron dense viroplasm of varied shapes present in the cytoplasm. Bacilliform particles may be seen budding into the ER lumen near the viroplasm. These particles resemble those of members of the Rhabdoviridae, but are shorter. The only sequenced virus of this group, orchid fleck virus (OFV), has a negative sense (bipartite) type ssRNA genome, but its organization is similar to known rhabdoviruses, which are monopartite. Both types of cytopathological effects have been found associated with citrus leprosis. In orchids, OFV has a 'nuclear type' of cytopathology, but in some species the 'cytoplasmic type' has been found associated with ringspot symptoms. In Hibiscus and Clerodendron, green spot symptoms have been associated with the cytoplasmic type of cell alteration, while chlorotic spots, in the same species, are associated with the nuclear type. In a few cases, both types of cytopathological effects have been found in the same tissue and cell.

Animals↗

PubMed2003

Citrus leprosis virus vectored by Brevipalpus phoenicis (Acari: Tenuipalpidae) on citrus in Brazil.

Citrus leprosis is caused by Citrus leprosis virus (CiLV) that is transmitted by mites in the genus Brevipalpus (Acari: Tenuipalpidae). This disease directly reduces production and the life span of the citrus plant. The main symptoms of the disease include lesions on fruits, leaves, and twigs or small branches, causing premature fruit drop, defoliation, and death of the twigs or branches leading to serious tree decline. Leprosis is a highly destructive disease of citrus, wherever it occurs. The Brazilian citrus industry spends over 100 million US dollars annually on acaricides to control the vector, Brevipalpus phoenicis (Geijskes). This review contains information about the history of the etiology of citrus leprosis, its geographical distribution, host range, the role of the mite vectors, viral morphology and relationships with the infected cell, and transmissibility of the virus by the mite. In addition, data on the mite-virus-plant relationship, disease damage, and strategies for controlling disease spread are presented.

Animals↗

PubMed2003

Citrus leprosis and its status in Florida and Texas: past and present.

According to published reports from 1906 to 1968, leprosis nearly destroyed the Florida citrus industry prior to 1925. This was supported with photographs showing typical leprosis symptoms on citrus leaves, fruit, and twigs. Support for the past occurrence of citrus leprosis in Florida includes: (1) presence of twig lesions in affected orange blocks in addition to lesions on fruits and leaves and corresponding absence of similar lesions on grapefruit; (2) yield reduction and die-back on infected trees; and (3) spread of the disease between 1906 and 1925. Transmission electron microscopy (TEM) examination of tissue samples from leprosis-like injuries to orange and grapefruit leaves from Florida in 1997, and fruits from grapefruit and sweet orange varieties from Texas in 1999 and 2000 did not contain leprosis-like viral particles or viroplasm inclusions. In contrast, leprosis viroplasm inclusions were readily identified by TEM within green non-senescent tissues surrounding leprosis lesions in two of every three orange leaf samples and half of the fruit samples obtained from Piracicaba, Brazil. Symptoms of leprosis were not seen in any of the 24,555 orange trees examined across Florida during 2001 and 2002. The authors conclude that citrus leprosis no longer exists in Florida nor occurs in Texas citrus based on: (1) lack of leprosis symptoms on leaves, fruit, and twigs of sweet orange citrus varieties surveyed in Florida: (2) failure to find virus particles or viroplasm inclusion bodies in suspect samples from both Florida and Texas examined by TEM; (3) absence of documented reports by others on the presence of characteristic leprosis symptoms in Florida; (4) lack of its documented occurrence in dooryard trees or abandoned or minimal pesticide citrus orchard sites in Florida. In view of the serious threat to citrus in the U.S., every effort must be taken to quarantine the importation of both citrus and woody ornamental plants that serve as hosts for Brevipalpus phoenicis (Geijskes), B. californicus (Banks), and B. obovatus Donnadieu (Acari: Tenuipalpidae) from countries where citrus leprosis occurs.

Animals↗

PubMed2003

Coffee ringspot virus vectored by Brevipalpus phoenicis (Acari: Tenuipalpidae) in coffee.

Coffee ringspot is characterized by conspicuous ringspot symptoms on leaves, berries, and less frequently on twigs. It is caused by coffee ringspot virus (CoRSV), a short, bacilliform virus (40 nm x 100-110 nm). The virus is not seed borne and is transmitted by Brevipalpus phoenicis (Geijskes). Transovarial transmission within the mite does not occur. CoRSV has been mechanically transmitted to Chenopodium amaranticolor Coste and Reynaud, C. quinoa Wildenow, Beta vulgaris L., and Alternanthera tenella Colla resulting in local lesions. Systemic infection within both C. amaranticolor and C. quinoa occurs. Virions are found in the nucleus or cytoplasm of infected cells, commonly associated with membranes. Occasionally, membrane bounded particles are found within the cisternae of the endoplasmic reticulum. A characteristic electron lucent, nuclear inclusion is commonly found in many infected cells. These cytopathic effects place CoRSV among the nuclear type of Brevipalpus-borne viruses. The disease has been reported in several Brazilian states (São Paulo, Paraná, Minas Gerais, and Federal District) and recently found in Costa Rica. A similar disease is known in the Philippines, but no information exists about its relationship to CoRSV. Coffee ringspot had no economical significance until recently when a large scale infection was reported in Minas Gerais that resulted in yield loss.

Animals↗

PubMed2003

Passion fruit green spot virus vectored by Brevipalpus phoenicis (Acari: Tenuipalpidae) on passion fruit in Brazil.

Passion fruit green spot disease was first identified in 1997 after a severe outbreak at Vera Cruz County, state of São Paulo, Brazil. Mature yellow fruits of Passiflora edulis Simms f. flavicarpa Degener showed characteristic green spots, 2-5 mm in diameter and patches of green tissues were present on senescent leaves. The devastating effect to passion flower is caused by necrotic lesions that encircle the stems and kill the plant. In severe cases, entire orchards of a few hectares in size have been completely destroyed. The disease was always preceded by heavy infestations of Brevipalpus phoenicis (Geijskes) (Acari: Tenuipalpidae). Transmission electron microscopy of affected tissues (fruits, leaves, and stems) consistently revealed the presence of short, bacilliform particles (50-70 nm x 100-120 nm) in the cisternae of the endoplasmic reticulum, as well as the presence of a dense viroplasm in the cytoplasm. This cytopathic effect has been found in several other Brevipalpus-transmitted or associated viruses and is classified as a cytoplasmic type of disease. Experimental reproduction of the leaf and stem symptoms was achieved by transferring B. phoenicis collected from affected field passion flower plants onto healthy plants. The evidence supports a viral etiology for the disease and the agent was named passion fruit green spot virus. Its relationship with other B. phoenicis related viruses continues to be studied. The disease was also found in the Brazilian states of Bahia, Sergipe, Rondonia, Minas Gerais, Rio de Janeiro, and in the Federal District. Use of one or more of the following acaricides (hexythiazox, fenbutatin-oxide, propargite, quinomethionate, or dicofol) has significantly reduced the incidence of the disease.

Animals↗

PubMed2002

Potyviruses, novel and known, in cultivated and wild species of the family Apiaceae in Australia.

Three potyviruses were identified by gene sequencing and found to be widespread in species of Apiaceae in Australia. Only celery mosaic virus was found in celery crops and in one of 180 specimens of feral carrot ( Daucus carota). Another related but distinct novel potyvirus, carrot virus Y, was the only virus found in carrot crops and all except one feral carrot. A more distantly related novel potyvirus, apium virus Y, was found in plants of sea celery ( Apium prostratum), cultivated parsley ( Petroselinum crispum) and the immigrant weed species poison hemlock ( Conium maculatum). These three potyviruses, together with celery yellow mosaic virus of South America and the closely related carrot thin leaf virus and carrot virus B of North America, form a distinct subgenus of the Potyviridae most closely related to turnip mosaic virus and two potyviruses of yam; yam mosaic virus from the Ivory Coast and Japanese yam mosaic virus. Celery mosaic and carrot virus Y are probably recent migrants to Australia, but apium virus Y may have been endemic longer. In ELISA tests using polyclonal antibodies against virions of celery mosaic virus, some isolates of carrot virus Y were indistinguishable from celery mosaic virus, whereas others gave smaller absorbancy values, and those of apium virus Y did not react. This study shows the value of virus identification based on gene sequencing for planning control measures.

Amino Acid Sequence↗

PubMed2002

Genomics and X-ray microanalysis indicate that Ca2+ and thiols mediate the aggregation and adhesion of Xylella fastidiosa.

The availability of the genome sequence of the bacterial plant pathogen Xylella fastidiosa, the causal agent of citrus variegated chlorosis, is accelerating important investigations concerning its pathogenicity. Plant vessel occlusion is critical for symptom development. The objective of the present study was to search for information that would help to explain the adhesion of X. fastidiosa cells to the xylem. Scanning electron microscopy revealed that adhesion may occur without the fastidium gum, an exopolysaccharide produced by X. fastidiosa, and X-ray microanalysis demonstrated the presence of elemental sulfur both in cells grown in vitro and in cells found inside plant vessels, indicating that the sulfur signal is generated by the pathogen surface. Calcium and magnesium peaks were detected in association with sulfur in occluded vessels. We propose an explanation for the adhesion and aggregation process. Thiol groups, maintained by the enzyme peptide methionine sulfoxide reductase, could be active on the surface of the bacteria and appear to promote cell-cell aggregation by forming disulfide bonds with thiol groups on the surface of adjacent cells. The enzyme methionine sulfoxide reductase has been shown to be an auxiliary component in the adhesiveness of some human pathogens. The negative charge conferred by the ionized thiol group could of itself constitute a mechanism of adhesion by allowing the formation of divalent cation bridges between the negatively charged bacteria and predominantly negatively charged xylem walls.

Bacterial Adhesion↗

PubMed1998

Molecular characterization of tomato spotted Wilt virus defective interfering RNAs and detection of truncated L proteins.

Junction sites of 25 different defective interfering (DI) RNAs of tomato spotted wilt virus (TSWV) were characterized. The DI RNAs varied in size from 2.0 to 5.2 kilobases (kb) and contained a single internal deletion. The absence of DI RNAs smaller than 2 kb suggested a size constraint for the survival of TSWV DI RNAs. This hypothesis was reinforced by the finding of a dimeric DI RNA formed by two 1.6-long monomers linked head to tail. Three types of junction sites were found, one type originating from a simple deletion; the second type contained a few extra nucleotides of unknown origin; and the third type contained a stretch of three to five nucleotides, originally occurring at both sides of the deletion and of which one was deleted. In 19 of the 25 DI RNAs studied, the original reading frame was maintained, suggesting a selective preference of DI RNAs with translational potency. Truncated proteins encoded by these DI RNAs were indeed detected in the nucleocapsid preparations. Folding studies of the complete L RNA revealed that the calculated minimal energy of folding was at 16 degreesC lower than at 23 degrees, indicating a higher stability of this molecule at low temperatures. The results suggest an involvement of locally folded secondary structures in the process of deletion, rather than the requirement of certain sequences around the deletion point. The DI RNA generation in TSWV is essentially, as discussed, similar to the process of RNA recombination described in many viruses.

Base Sequence↗

PubMed1998

Morphological and molecular characterization of the poxvirus BeAn 58058.

BeAn 58058 virus (BAV) was isolated from an Oryzomis rodent in Brazil. BAV was shown to be antigenically related to another poxvirus also isolated in Brazil, the Cotia virus, but it remained ungrouped. Electron microscopy revealed that BAV has a typical poxvirus morphology. The Hind III DNA profile of BAV genome was similar with that of VV WR and Lister, but some differences in the profile were detected. We have also detected the presence of genes homologous to vaccinia virus (VV WR) genes in the genome of BAV. Genes related to vaccinia thymidine kinase (TK) gene and vaccinia growth factor (VGF) gene were found. The patterns of TK and VGF mRNA transcripts described for vaccinia virus infected cells were observed in BAV infected cells. Nucleotide sequence of BAV VGF homologous gene was similar to VV WR VGF sequences. This similarity was further seen when cross-hybridization of total genomes of BAV and VV was done. Polypeptide synthesis of BAV and vaccinia in infected cells also showed similar profiles. The genetic data was used to construct a phylogenetic tree where BAV and VV were placed at the same cluster. Based on our findings we propose that BAV is a vaccinia virus variant.

Amino Acid Sequence↗

PubMed1994

Detection of avocado sunblotch viroid in chloroplasts of avocado leaves by in situ hybridization.

In situ hybridization experiments were carried out to detect avocado sunblotch viroid (ASBVd) in foliar tissue of avocado, using a digoxigenin-labelled RNA probe complementary to the ASBVd-RNA in sections of aldehyde-fixed, LRGold-embedded leaf samples. Detection of the probe was made through anti-digoxigenin antibody and protein-A colloidal gold (20 nm). Seventy to 80% of the signals came from chloroplast while the cytoplasm and vacuole were labelled with ca. 10% of the gold particles. This is in contrast with the subcellular localization of potato spindle tuber viroid and some other related viroids, which are mainly found in the nucleus.

Chloroplasts↗

PubMed1994

Nucleotide sequence of the original Brazilian isolate of coleus yellow viroid from Solenostemon scutellarioides and infectivity of its complementary DNA.

The complete nucleotide (nt) sequence of the original coleus yellow viroid (CYVd) from Solenostemon scutellarioides, 'Golden Bedder', has been determined. The covalently closed single-stranded CYVd RNA molecule consists of 248 nt residues which assumes a rod-like secondary structure when folded in the model of lowest free energy. The sequence was determined by direct sequencing of RNA and from three overlapping cDNA clones. Comparison of the CYVd sequence with that of Coleus blumei viroid 1 (CbVd 1) from Germany demonstrated that they are closely related. The differences observed in the genome organization of CYVd relative to CbVd 1 were at three sites: position 25 (one U deletion), position 26 (a U was replaced by an A) and position 241 (one A insertion). The first two mutations were detected in one A-rich segment of eight nt (between positions 25 and 34). Northern blot hybridization of partially purified nucleic acids from the leaf tissue of S. scutellarioides 'Frilled Fantasy', inoculated with double-stranded cDNA, demonstrated that this fragment was infectious. These data enable CYVd to be assigned to the viroid class of plant pathogens, based on its biological properties and molecular structure. This work also gives additional support to the present classification system, in which the viroids isolated from S. scutellarioides form a distinct subgroup.

Base Sequence↗

PubMed1993

Distinct levels of relationships between tospovirus isolates.

The taxonomic relations of a number of tospovirus isolates, collected in different geographical areas and from different host plants, were studied. To delineate these isolates, properties such as susceptibility of a limited range of host plants, symptomatology, cytopathology, nucleocapsid composition, serology of their nucleocapsid proteins, and nucleotide sequence homology were compared. The results show that isolates which have previously been discriminated as members of three different serogroups, should in fact be regarded as representatives of at least three distinct virus species in the tospovirus genus.

Blotting, Northern↗

PubMed1992

Nomenclature and relationships of some Brazilian leguminous potyviruses related to bean common mosaic and/or passionfruit woodiness viruses.

The main Brazilian literature of the last 10 years on potyviruses of leguminous plants related to bean common mosaic virus (BCMV) and/or to passionfruit woodiness virus (PWV) is discussed and summarized. The viruses dealt with are canavalia acronecrosis, mosaico de canavalia, cassia yellow spot, cowpea green vein-banding, cowpea rugose mosaic and cowpea severe mottle. The viruses have similar biological properties, such as a host range restricted mainly to the Leguminosae, aphid transmission, seed transmission in leguminous plants, and various degrees of serological relationships with BCMV and PWV.

Brazil↗

PubMed1991

The nonstructural protein (NSs) encoded by the ambisense S RNA segment of tomato spotted wilt virus is associated with fibrous structures in infected plant cells.

The open reading frame located in the viral strand of the ambisense S RNA of tomato spotted wilt virus (TSWV), was cloned into transfer vector pAc33DZ1 and inserted downstream of the polyhedrin promoter in the Autographa californica nuclear polyhedrosis virus genome. Recombinant baculoviruses were obtained that showed a high-level expression of a 52.4-kDa protein corresponding to the inserted TSWV gene. The viral protein thus produced was purified and injected into rabbits to raise antibodies. Western immunoblot analyses of extracts from TSWV-infected plants demonstrated that the 52.4-kDa TSWV-specific polypeptide represents a nonstructural protein (denoted NSs), being absent in purified virus particles. Immunogold labeling of tissue sections of TSWV-infected Nicotiana rustica plants showed that this protein was, depending on the virus isolate, either found dispersed throughout the cytoplasm or associated with fibers which appeared as elongated flexible filaments or paracrystalline rods.

Animals↗

PubMed1991

Generation of envelope and defective interfering RNA mutants of tomato spotted wilt virus by mechanical passage.

During a series of mechanical transfers of tomato spotted wilt virus, two distinct types of mutants were generated. Firstly, a morphologically defective isolate was obtained which had lost the ability to produce the membrane glycoproteins and, as a consequence, was not able to form enveloped particles. Analysis of the genomic RNAs of this isolate suggested that this defect was caused by either point mutations or very small deletions in the medium genomic RNA segment. Secondly, isolates were obtained which had accumulated truncated forms of the large (L) RNA segment. These shortened L RNA molecules most likely represented defective interfering RNAs, since they replicated more rapidly than full-length L RNA and their appearance was often associated with symptom attenuation. Defective L RNAs of different sizes were generated after repeated transfers, and hybridization analysis using L RNA-specific cDNA probes showed that the internal regions deleted varied in length. The presence of defective L RNAs in nucleocapsid fractions as well as in enveloped virus particles indicates that all defective molecules retained the sequences required for replication, encapsidation by nucleocapsid proteins and packaging of the nucleocapsid into virus particles.

Blotting, Northern↗

PubMed1990

Serological differentiation of 20 isolates of tomato spotted wilt virus.

Twenty tomato spotted wilt virus (TSWV) isolates were serologically compared in ELISA employing five different procedures using a rabbit polyclonal antiserum against nucleocapsid proteins (NuAbR) and mouse monoclonal antibodies (MAbs), two directed to nucleocapsid proteins (N1 and N2) and four directed to glycoproteins G1 to G4. All the antisera were raised against TSWV-CNPH1. The 20 isolates were differentiated into two distinct serogroups. Serogroup I consisting of 16 isolates strongly reacted with NuAbR. The other four isolates were poorly recognized by NuAbR and were placed in another serogroup, designated II. The panel of MAbs differentiated the TSWV isolates into three serotypes. The 16 isolates forming serogroup I reacted strongly with the MAbs generated and were identified as serotype I isolates. The four isolates which made up serogroup II were split into serotypes II and III. The serotype II isolates did not respond or responded poorly with MAbs N1, N2 and G3. The two other isolates placed in serotype III were recognized by N1 but not by N2 and G3. Two isolates became defective after several mechanical passages and failed to respond or responded very poorly with MAbs directed to glycoproteins. Our results show that ELISA employing polyclonal and monoclonal antisera is a useful tool to differentiate TSWV isolates and to detect defective forms. The results also strongly suggest that TSWV nucleocapsid proteins are less conserved than the glycoproteins.

Antibodies, Monoclonal↗

PubMed1983

Electron microscopy of maize rayado fino virus in the internal organs of its leafhopper vector.

Discrete groups of 20- to 25-nm isometric particles, considered to represent maize rayado fino virus (RFV), were consistently observed in the ectoderm, fat body, midgut, follicular cells of the ovary, muscle, and salivary glands of RFV-infected Dalbulus maidis. The particles commonly occurred within cytoplasmic bodies bound by membranes, some of them resembling lysosomes, and were not found in nonviruliferous insects. These findings are congruent with previous studies on the multiplication of RFV in D. maidis. The absence of cytopathologic effects due to viral infection at the ultrastructural level confirms biological data on the absence of deleterious effects of the virus in its vector.

Animals↗