Determinants Of Host Specificity Research Articles

Evaluation of Colletotrichum gloeosporioides for Biological Control of Miconia calvescens in Hawaii.

Miconia calvescens (Melastomataceae), from the Neotropics, is a noxious forest weed in Hawaii. We evaluated an isolate of Colletotrichum gloeosporioides that causes leaf spots on Miconia spp. in Brazil for its potential in biological control. Hawaii has no native Melastomataceae genera but does have members of 12 introduced genera. Following Wapshere's centrifugal phylogenetic method (2), eight species of Melastomataceae genera in Hawaii were inoculated in addition to Miconia spp. Naturalized and native Hawaiian members of the order Myrtales also were inoculated to determine host specificity, including Terminalia catappa (Combretaceae); Cuphea hysopifolia and C. ignea (Lythraceae); Arthrostema ciliatum, Clidemia hirta, Dissotis rotundifolia, Heterocentron subtriplinervium, Medinilla scortechenii, Melastoma candidum, Pterolepsis glomerata, and Tibouchina herbaceae (Melastomataceae); Eucalyptus grandis, Eucalyptus microcorys, Eugenia reinwardtiana, Eugenia uniflora, Leptospermum laevigatum, Melaleuca quinquenervia, Metrosideros polymorpha, Psidium guajava, and Syzgium malaccanse (Myrtaceae); Fuchsia magellanica and Oenothera stricta (Onagraceae); and Wikstroemia oahuensis and W. uva-ursi (Thymelaeaceae). All M. calvescens plants were grown from seed collected in Hawaii. Other test plants were grown from seeds or cuttings in artificial potting medium in a greenhouse. Plants had 6 to 8 mature leaves when inoculated. C. gloeosporioides was cultured on 10% potato dextrose agar supplemented with plain agar (35 g/liter) and incubated under constant fluorescent illumination at 20°C. Conidia were harvested by flooding 10-to 14-day-old cultures with sterile tap water, followed by light scraping with a scalpel. Conidial suspensions were adjusted to 106 conidia per ml and applied to both leaf surfaces with a hand-held sprayer. Inoculated plants were kept at 100% relative humidity and 16 to 25°C for 48 h. Four replicate plants and one plant of M. calvescens per species were inoculated. Plants were observed for symptom development for up to 6 weeks. The entire test was repeated once. Lesions were visible after 7 to 10 days. Young lesions had chlorotic halos and expanded in a roughly circular pattern to diameters of 5 to 10 mm. Mature lesions developed necrotic centers, coalesced, and became dry and brittle with age, resulting in extensive leaf necrosis. Defoliation of moderately to severely infected leaves occurred ≈ 30 days after inoculation. With the exception of M. calvescens, C. gloeosporioides did not produce visible symptoms on test plants. The failure of Clidemia hirta, the taxonomic species most closely related to M. calvescens, to become symptomatic was particularly significant relative to the centrifugal phylogenetic concept. The results demonstrate that our pathogen (VIC 19306) is distinct from C. gloeosporioides f. sp. clidemiae (1), which did not infect M. calvescens. We designate our pathogen C. gloeosporioides f. sp. miconiae. Voucher specimens (VIC 19306, Sana, RJ, 24.II.1998, and R. W. Barreto) and cultures are maintained at the Departamento de Fitopatologia, Universidade Federal de Viçosa MG, Brazil.

Replication of nucleopolyhedroviruses of Autographa californica (Lepidoptera : Noctuidae), Bombyx mori (Lepidoptera : Bombycidae), Hyphantria cunea (Lepidoptera : Arctiidae), and Spodoptera exigua (Lepidoptera : Noctuidae) in four lepidopteran cell lines

Four different NPV isolates from Autographa californica (AcNPV), Bombyx mori (BmNPV), Hyphantria cunea (HcNPV) and Spodoptera exigua (SeNPV) were characterized for their biological properties in four lepidopteran cell lines which were derived from S. frugiperda (IPLB-Sf-21), B. mori (BmN-4), Spilosoma imparilis (FRI-Splm-1229), and S. exigua (Se301). On the basis of the data on viral DNA replication, viral structural protein synthesis, budded virion (BV) yield, polyhedrin synthesis, and polyhedral formation in the infected cells, it was demonstrated that each of these NPV isolates established specific interactions with the respective cell lines. Of 16 NPV-cell systems examined, three NPV-cell systems exhibited two different types of abortive infection. In HcNPV-infected BmN-4 cells, viral DNA replication occurred but the infection aborted at the step prior to late gene expression, whereas both AcNPV-infected BmN-4 cells and HcNPV-infected IPLB-Sf-21 cells yielded BVs into culture medium but were defective in polyhedrin expression. In addition, it was found that SeNPV exhibited a unique infection process in FRI-SpIm-1229 cell cultures, in which viral DNA replicated and a limited number of polyhedra were formed in a restricted number of infected cells while few, if any, progeny BVs were produced and a significant proportion of infected cells displayed apoptotic-like morphology. The present study, thus, developed various NPV-cell systems which facilitate the analysis of molecular mechanisms underlying baculovirus host specificity determination.

Genome plasticity in the distal tail fiber locus of the T-even bacteriophage: recombination between conserved motifs swaps adhesin specificity

The adsorption specificity of the T-even phages is determined by the protein sequence near the tip of the long tail fibers. These adhesin sequences are highly variable in both their sequence and specificity for bacterial receptors. The tail fiber adhesin domains are located in different genes in closely related phages of the T-even type. In phage T4, the adhesin sequence is encoded by the C-terminal domain of the large tail fiber gene (gene 37), but in T2, the adhesin is a separate gene product (gene 38) that binds to the tip of T2 tail fibers. Analysis of phage T6 and Ac3 sequences reveals additional variant forms of this locus. The tail fiber host specificity determinants can be exchanged, although the different loci have only limited homology. Chimeric fibers can be created by crossovers either between small homologies within the structural part of the fiber gene or in conserved motifs of the adhesin domain. For example, the T2 adhesin determinants are flanked by G-rich DNA motifs and exchanges involving these sequences can replace the specificity determinants. These features of the distal tail fiber loci genetically link their different forms and can mediate acquisition of diverse host range determinants, including those that allow it to cross species boundaries and infect taxonomically distant hosts.

Determination of host specificity of cowpea miscellany Rhizobium spp. by nodABC-lacZ fusion.

Cowpea miscellany group of rhizobia are generally broad host range. Transconjugants of these cowpea rhizobial isolates having nodABC-lacZ fusion were monitored for flavonoid/root exudate-induced activation of the nod genes in terms of beta-galactosidase activity, thus determining the potential host range of the rhizobial isolates.

Indigestion, Not Scorched Earth, Beats Alien Hookworms?

There is a poor correlation between measurable immune responses to hookworms, the intensity of gut inflammation, and the longevity of hookworms which, in the case of A. caninum in the human intestine, is consistently and markedly limited.Parasite survival depends on a multitude of factors, beginning with an ability to negotiate host anatomy. That larvae of canine hookworms can read internal human signposts is remarkable, but does indicate molecular similarities between tissues of different hosts. When L4 arrive in the intestine, they anchor and feed normally initially, but then seem to run out of energy, to succumb at about three weeks. Immune and inflammatory responses at about this time are not particularly unique or aggressive, for the event is clinically silent in most infected people.Croese accepts that `other hookworms are smaller than normal when found outside the specific host', and that `rapid [hookworm intestinal] transit would restrict the possibilities for the digestion and absorption of complex constituents'[1xSee all References[1]. He acknowledges that the worm might not be able to derive sufficient nutrient from its host. By assuming that parasite nutrition depends on simple molecules absorbed from host blood, he forgets that the worm's digestive enzymes commence working externally, to predigest mucosal tissues. Further, while transit through the worm intestine seems rapid from our perspective, we must remember the scale at which all this is happening! And the worms do not pump food continuously; periods of rest allow for more complete digestion and absorption of material within its own gut.This begs the question: how compatible are parasite enzymes with their substrates, ie. host tissues? If hookworm digestive physiology is working at the limits of its capacity to support the rapidly growing juvenile, the enzymes that predigest host tissues, and continue the process in the worm's gut, must function optimally. A modest reduction in host-mucosal breakdown or haemolysis (assuming blood and mucosa are equally important nutrient sources) could jeopardize parasite development and survival (perhaps via resistance to inflammatory damage?). If constituent proteins in canine gut mucosa and blood vary slightly from those of humans, the corresponding hookworm enzymes would be expected also to vary slightly. Such differences might be indiscernible by immunological probes, but possibly not by molecular and enzyme kinetic studies. Notwithstanding the cross-species activity of secreted hookworm anticoagulants and NIF, Croese acknowledges that in these closely related parasites, `It seems probable that some excretory/secretory molecules are subtly and crucially unique, and that these differences determine host specificity'.In effect, the worm starves. This might also lead to a form of `immunosuppression' in the worm, ie. a decline in output of host-immunomodulating factors (and so indirectly allow intense EE in some patients).Congruity between host proteins and parasite enzymes might underlie host-specificity in a wide range of haematophagous parasites, but has not been examined in this context.It remains to explain the experimental establishment of hookworms in abnormal hosts. While A. ceylanicum, normally parasitic in dogs and cats, has been established in hamsters, only neonatal animals are susceptible. Apart from immature immune systems, neonatal mammals have high levels of foetal haemoglobin, which might vary less between species than does adult haemoglobin. A. duodenale has been established in dogs, which initially were immunosuppressed. While this might suggest that immunity is important, immunosuppressive therapy, especially that involving corticosteroids, has a diversity of biochemical and physiological effects on most body systems, which indirectly may favour hookworm survival. Steroids might even mimic helminthic ecdysterones, and so directly stimulate growth and development of some parasites, as has been speculated for Strongyloides stercoralis[8xGenta, R.M. Clin. Microbiol. Rev. 1992; 5: 345–355PubMedSee all References[8].Finally, it must be recognized that successfully established laboratory models of A. duodenale in dogs represent selected strains of both parasite and host. This `directed evolution' does not need immunological explanations. If the strains of A. caninum that develop in the human intestine could be subcultured in immunosuppressed children, before too long we should have a successful model of canine hookworm infection in human hosts!

The life history and host range of Ectagagarcia, a biological control agent for Lantana camra and L. montevidensis in Australia

The life cycle and host specificity of Ectaga garcia were investigated. Moths emerge in the morning and are inactive during the day. Eggs are laid and larvae feed on the undersurface of leaves of Lantana camara and L. montevidensis. Larvae spin protective cocoons from which they feed and in which they pupate. Development from egg to adult takes approximately 48 days. Forty-five plant species were tested to determine host specificity. Females laid eggs only on L. camara and L. montevidensis. In no-choice trials, neonate larvae fed but failed to complete development on nine test species. E. garcia was subsequently approved for release in Australia.

Replication of alfalfa mosaic virus RNA 3 with movement and coat protein genes replaced by corresponding genes of Prunus necrotic ringspot ilarvirus.

Alfalfa mosaic virus (AMV) and Prunus necrotic ringspot virus (PNRSV) are tripartite positive-strand RNA plant viruses that encode functionally similar translation products. Although the two viruses are phylogenetically closely related, they infect a very different range of natural hosts. The coat protein (CP) gene, the movement protein (MP) gene or both genes in AMV RNA 3 were replaced by the corresponding genes of PNRSV. The chimeric viruses were tested for heterologous encapsidation, replication in protoplasts from plants transformed with AMV replicase genes P1 and P2 (P12 plants) and for cell-to-cell transport in P12 plants. The chimeric viruses exhibited basic competence for encapsidation and replication in P12 protoplasts and for a low level of cell-to-cell movement in P12 plants. The potential involvement of the MP gene in determining host specificity in ilarviruses is discussed.

Hop stunt viroid (HSVd) sequence variants from Prunus species: evidence for recombination between HSVd isolates.

Hop stunt viroid (HSVd) is able to infect a number of herbaceous and woody hosts, such as grapevine, Citrus or Prunus plants. Previous phylogenetic analyses have suggested the existence of three major groups of HSVd isolates (plum-type, hop-type and citrus-type). The fact that these groups often contain isolates from only a limited number of isolation hosts prompted the suggestion that group-discriminating sequence variations could, in fact, represent host-specific sequence determinants which may facilitate or be required for replication in a given host. In an effort to further understand the relationships between HSVd and its different hosts, HSVd variants from eight naturally infected Prunus sources, including apricot, peach and Japanese plum have been cloned and sequenced. In total, ten molecular variants of HSVd have been identified, nine of which have not been described before. A detailed phylogenetic analysis of the existing HSVd sequences, including the new ones from Prunus determined in this work, points towards a redefinition of the grouping of variants of this viroid, since two new groups were identified, one of them composed of sequences described here. A bias for the presence of certain sequences and/or structures in certain hosts was observed, although no conclusive host-determinants were found. Surprisingly, our analysis revealed that a number of HSVd isolates probably derived from recombination events and that the previous hop-type group itself is likely to be the result of a recombination between members of the plum-type and citrus-type groups.

Molecular Studies on Bromovirus Capsid Protein

Two members of the bromovirus group, brome mosaic virus (BMV) and cowpea chlorotic mottle virus (CCMV), selectively infect barley and cowpea, respectively, and also differ in their ability to systemically infect a common permissive host,Chenopodium quinoa.CCMV is confined to inoculated leaves ofC. quinoa,whereas BMV causes rapid systemic mottling. To examine whether host-specific determinants for systemic movement of BMV and CCMV in each of these hosts are localized in the coat protein (CP), sequences encoding this gene were exchanged between biologically active clones of BMV RNA3 (B3) and CCMV RNA3 (C3) to create chimera expressing heterologous CP genes (B3/CCP and C3/BCP). Inoculation of each chimera with its respective wild-type (wt) RNAs 1 and 2 to barley or cowpea orC. quinoaplants resulted in symptom phenotype and long distance movement characteristics similar to those of the parental virus donating RNAs 1 and 2. These observations suggest that neither BMV CP nor CCMV CP has host-specific determinants for long distance movement. Inoculation of additional recombinant viruses, constructed by reassorting wt genomic RNAs 1 and 2 of BMV and CCMV with either heterologous wt RNA3 (i.e., B1+B2+C3 and C1+C2+B3) or heterologous chimeric RNA3 (i.e., B1+B2+C3/BCP and C1+C2+B3/CCP), to susceptible hosts resulted only in localized infections. The significance of these observations in relation to bromovirus movement is discussed.

The hsd loci of Mycoplasma pulmonis: organization, rearrangements and expression of genes.

Two paralogous, site-specific invertible loci, designated hsd1 and hsd2 (host specificity determinant), have been identified in the Mycoplasma pulmonis genome. They encode putative type I restriction and modification (R-M) systems with maximum sequence homology to the type IC family, which includes EcoR124II and EcoDXXI. Each locus encodes an endonuclease subunit (HsdR), a methylase subunit (HsdM) and two DNA specificity subunits (HsdS). The gene organization at each locus is such that hsdR and hsdM are flanked by two hsdS genes. Within each locus, one of the hsdS genes, hsdR and hsdM, is encoded in tandem by the same DNA strand, while the second hsdS gene is encoded by the complementary strand but without overlap with the other three hsd genes. The hsdR and hsdM sequences of one locus are almost identical to their counterparts in the other. The four hsdS genes (two per locus) are highly homologous at their 5' ends and also share sequence similarities in the 3' ends of their corresponding coding regions. Owing to the disposition of and sequence similarities among the hsdS genes, they form inverted repeats at each locus. Analysis by polymerase chain reaction (PCR) has shown that both loci behave as site-specific DNA invertible elements with multiple inversion sites, termed 'vipareetus', occurring within the hsdS genes. The inversions lead to a reassortment of hsdS sequences, generating an array of recombinant genes that probably encode S subunits possessing alternative DNA-binding specificities. Sequence information obtained from the analysis of hsd2 transcripts by 5' RACE (rapid amplification of cDNA ends) indicates that inversion induces the transcription of alternative hsdS genes by the relocation of coding sequences downstream of a promoter and ribosome-binding site (RBS) situated at one end of each locus.

Molecular mechanisms of Nod factor diversity.

The rhizobia-legume symbiosis is highly specific. Major host specificity determinants are the bacterial Nod factor signals that trigger the nodulation programme in a compatible host. Nod factors are lipo-chitooligosaccharides (LCOs) varying in the oligosaccharide chain length, the nature of the fatty acids and substitutions on the oligosaccharide. The nod genotype of rhizobia, which forms the genetic basis for this structural variety, includes a set of nodulation genes encoding the enzymes that synthesize LCOs. Allelic and non-allelic variation in these genes ensures the synthesis of different LCO structures by the different rhizobia. The nod genotypes co-evolved with host plant divergence in contrast to the rhizobia, which followed a different evolution. Horizontal gene transfer probably played an important role during evolution of symbiosis. The nod genotypes are particularly well equipped for horizontal gene transfer because of their location on transmissible plasmids and/or on 'symbiosis islands', which are symbiotic regions associated with movable elements.

Spirocamallanus species of French Polynesian coral reef fishes

Spirocamallanus monotaxis is redescribed from Monotaxis grandoculis (Lethrinidae) and reported from 10 other species of coral reef associated fishes from both the Society Islands and the Tuamotu Islands. This represents a new locality for S. monotaxis and 10 new host records. Spirocamallanus colei n.sp. is described from Acanthurus achilles (Acanthuridae) and from Acanthurus guttatus, Acanthurus lineatus, Acanthurus triostegus, and Zebrasoma scopas from both the Society Islands and the Tuamotu Islands. Spirocamallanus chaimha n.sp. is described from Ctenochaetus striatus and Acanthurus olivaceous (Acanthuridae) from Moorea in the Society Islands. The number of buccal capsule ridges in Spirocamallanus varies and minor differences have no taxonomic importance. Marine Spirocamallanus species appear to belong to a single clade characterized by 3 preanal papillae and 5 postanal papillae. This clade may be subdivided on the basis of the shape of the female tail. In French Polynesia, ecological factors as opposed to phylogenetic factors appear to determine host specificity for Spirocamallanus. A new system of reporting the positions of the caudal papillae, based on the position of the papillae relative to the length of the alae, is used.

Replicase proteins as determinants of phloem-dependent long-distance movement of tobamoviruses in tobacco

The establishment of a systemic infection by a virus requires movement of viral progeny through the phloem. The extent to which viral components act as host-specific determinants of phloem-dependent movement is unknown. We have examined the roles that the sunn-hemp mosaic tobamovirus (SHMV) encoded proteins play as host-dependent determinants of phloem-dependent movement in tobacco (Nicotiana tabacum) to see what viral product mediates this process. SHMV moves from cell to cell in inoculated leaves of tobacco, but fails to establish a systemic infection characteristic of tobacco mosaic tobamovirus (TMV). To determine if the SHMV coat protein (CP) alone or the SHMV movement protein (MP) and CP together are factors in establishing a systemic infection by SHMV in tobacco, the SHMV-CP gene was exchanged for the TMV-CP gene in two full-length TMV cDNA clones (pTSCP and pTSCP47) and a full-length TMV cDNA clone containing a defective TMV-MP gene (pTMfSCP47). RNA transcripts from pTSCP and pTSCP47 or pTMfSCP47 efficiently induced systemic infections in tobacco or transgenic tobacco plants expressing the SHMV-MP gene, respectively. The data indicate that the SHMV CP or SHMV MP and CP together can function to establish a systemic infection, inferring that the replication-associated proteins of SHMV may be determinants of phloem-dependent movement in tobacco.

A new hepadnavirus endemic in arctic ground squirrels in Alaska.

We present evidence for a novel member of the hepadnavirus family that is endemic in wild arctic ground squirrels (Spermophylus parryi kennicotti) in Alaska. This virus, designated arctic squirrel hepatitis virus (ASHV), was initially detected in the livers of animals bearing large hepatic nodules by nucleic acid hybridization with hepadnavirus probes and in plasma by cross-reactivity with antibodies to hepadnavirus surface and core antigens. The complete nucleotide sequence of the 3,302-bp-long ASHV genome was determined and compared with those of ground squirrel hepatitis virus (GSHV) and woodchuck hepatitis virus (WHV); all sequences were organized into four open reading frames, designated pre-C/C, pre-S/S, pol, and X. Despite roughly equivalent variability among the three rodent hepadnaviruses (around 16% base and 19% amino acid exchanges), ASHV appeared to be more closely related to GSHV than to WHV in phylogenetic analysis. Accordingly, preliminary studies of the pathology of ASHV infection suggested that ASHV may be a less efficient oncogenic agent than WHV. About one-third of aged animals maintained in captivity, including virus-infected as well as uninfected squirrels, developed large liver nodules, consisting of hepatocellular adenomas or carcinomas or nonmalignant lesions characterized by drastic microvesicular steatosis. ASHV-infected arctic ground squirrels may serve as a new model with which to analyze the contribution of hepadnavirus- and host-specific determinants to liver pathology and tumorigenesis.

Rhizobium nodulation protein NodA is a host-specific determinant of the transfer of fatty acids in Nod factor biosynthesis.

In the biosynthesis of lipochitin oligosaccharides (LCOs) the Rhizobium nodulation protein NodA plays an essential role in the transfer of an acyl chain to the chitin oligosaccharide acceptor molecule. The presence of nodA in the nodABCIJ operon makes genetic studies difficult to interpret. In order to be able to investigate the biological and biochemical functions of NodA, we have constructed a test system in which the nodA, nodB and nodC genes are separately present on different plasmids. Efficient nodulation was only obtained if nodC was present on a low-copy-number vector. Our results confirm the notion that nodA of Rhizobium leguminosarum biovar viciae is essential for nodulation on Vicia. Surprisingly, replacement of R. l. by viciae nodA by that of Bradyrhizobium sp. ANU289 results in a nodulation-minus phenotype on Vicia. Further analysis revealed that the Bradyrhizobium sp. ANU289 NodA is active in the biosynthesis of LCOs, but is unable to direct the transfer of the R. l. by, viciae nodFE-dependent multi-unsaturated fatty acid to the chitin oligosaccharide acceptor. These results lead to the conclusion that the original notion that nodA is a common nod gene should be revised.

The role of Nod signal structures in the determination of host specificity in the Rhizobium-legume symbiosis

During the past five years the structure of nodulation signals from more than a dozen different Rhizobium species has been elucidated. In addition, the role of numerous nod genes in the biosynthesis of the lipooligosaccharides has been identified. This review discusses how Nod signal structure is determined by the specificity of the various biosynthetic steps and how this influences variation in host specificity. Until recently, it appeared that the decorations of a common lipochitooligosaccharide core determine the host-specific recognition of the signals, possibly via specific receptors in the host plant cell. A number of recent publications, however, suggest that beyond the interaction of Nod signals with a putative receptor, certain structural features of Nod factors are involved in controlling the concentration of the signals during their uptake by the root tissue.

Metarhizium spore surface antigens are correlated with pathogenicity

An antiserum produced to intact spores of an isolate of Metarhizium anisopliae (DAT F-001), which is pathogenic to Adoryphorus couloni, was used to determine the ELISA-index (DAS-ELISA) of 49 isolates of M. anisopliae. The ELISA-index gave a measure of the level of spore surface antigens present in spore populations of each isolate. The virulence of the 49 isolates was determined by bioassay and ranged from non-pathogenic to highly virulent. The virulence of the isolates was correlated with the ELISA-index. We suggest that the spore surface antigens of M. anisopliae are the primary determinant of host-specificity.

Open-field Tests in Host-specificity Determination of Insects for Biological Control of Weeds

Open-field tests may be used for the host-specificity determination of insects used in the biological control of weeds. Such tests allow insects to exercise free choice of plants without constraints associated with the use of cages. Therefore, this testing method can generate host data on candidate biocontrol agents under more natural conditions than those obtained via cage tests. The literature contains 24 studies of open-field testing, involving 13 target weed species, more than 34 species of insects and one eriophyid mite. Field-test data were used to support the release of 20 of these candidate agents into new countries. Most field tests have been conducted in concert with laboratory host-specificity tests or in response to the results of laboratory tests. This review also provides information on experimental designs, locations, categories of test plants included and the constraints of open-field testing.

Mutation or Increased Copy Number of nodE Has No Effect on the Spectrum of Chitolipooligosaccharide Nod Factors Made By Rhizobiumleguminosarum bv. trifolii

The bacterial gene nodE is the key determinant of host specificity in the Rhizobium leguminosarum-legume symbiosis and has been proposed to determined unique polyunsaturated fatty acyl moieties in chitolipooligosaccharides (CLOS) made by the bacterial symbiont. We evaluated nodE function by examining CLOS structures made by wild-type R. leguminosarum bv. trifolii ANU843, an isogenic nodE::Tn5 mutant, and a recombinant strain containing multiple copies of the pSym nod region of ANU843. 1H-NMR, electrospray ionization mass spectrometry, fast atom bombardment mass spectrometry, flame ionization detection-gas chromatography, gas chromatography/mass spectrometry, and high performance liquid chromatography/UV photodiode array analyses revealed that these bacterial strains made the same spectrum of CLOS species. We also found that ions in the mass spectra which were originally assigned to nodE-dependent CLOS species containing unique polyunsaturated fatty acids (Spaink, H. P., Bloemberg, G. V., van Brussel, A. A. N., Lugtenberg, B. J. J., van der Drift, K. M. G. M., Haverkamp, J., and Thomas-Oates, J. E. (1995) Mol. Plant-Microbe Interact. 8, 155-164) were actually due to sodium adducts of the major nodE-independent CLOS species. No evidence for nodE-dependent CLOSs was found for these strains. These results indicate a need to revise the current model to explain how nodE determines host range in the R. leguminosarum-legume symbiosis.

Identification of Tomato Bushy Stunt Virus Host-Specific Symptom Determinants by Expression of Individual Genes from a Potato Virus X Vector

Identification of Tomato Bushy Stunt Virus Host-Specific Symptom Determinants by Expression of Individual Genes from a Potato Virus X Vector