Nitrogen-fixing chemo-organotrophic bacteria isolated from cyanobacteria-deprived lichens and their ability to solubilize phosphate and to release amino acids and phytohormones

AIMS

Cyanobacteria-deprived lichens of the species Canoparmelia caroliniana, Canoparmelia crozalsiana, Canoparmelia texana, Parmotrema sancti-angeli and Parmotrema tinctorum were screened for the presence of chemo-organotrophic nitrogen-fixing bacteria.

METHODS AND RESULTS

Fifty-three lichen samples subjected to enrichment selection using a nitrogen-free minimal medium were positive for acetylene reduction. Seventeen isolates, able to fix nitrogen, belonged to Gamma-proteobacteria group and were identified as: Acinetobacter sp., Pantoea sp., Pseudomonas sp., Pseudomonas stutzeri, Serratia marcescens and Stenotrophomonas maltophilia, according to 16S rRNA gene sequences and biochemical tests. The excretion of amino acid and phytohormone and the ability of mineral phosphate solubilization were determined in 14 isolates. All isolates were able to release amino acids and 3-indoleacetic acid. About 64% of the isolates solubilized phosphates and 30% released ethylene.

CONCLUSIONS

These data confirm sparse evidence from the literature on the occurrence of chemo-organotrophic nitrogen-fixing bacteria in cyanobacteria-deprived lichens; the isolates presented physiologic features which might benefit the host if they are expressed when the bacteria are harboured by lichens.

SIGNIFICANCE AND IMPACT OF THE STUDY

Chemo-organotrophic nitrogen-fixing bacteria were isolated from a high percentage (72.6%) of cyanobacteria-deprived lichens. All isolates presented important physiological characteristics, some of which are being described here for the first time.

Identification of the minimal sequence required for vascular-specific activity of Tomato mottle Taino virus Replication-associated protein promoter in transgenic plants

A 597 nt fragment from Tomato mottle Taino virus (ToMoTV) DNA-A, with 459 nt located upstream of the Replication-associated protein translation start codon, was tested for promoter activity in solanaceous plants. The promoter activity of this fragment (pRep(459::Rep)) was demonstrated when it was introduced upstream the uidA reporter gene into tobacco, potato and tomato plants by genetic transformation. It became active in 7-day-old transgenic tobacco seedlings as revealed by a vascular-specific pattern of gene expression which was maintained during the continued growth of the plant. Transformed potato and tomato plants also showed a vascular-specific pattern of expression. In comparative assays, pRep(459::Rep) showed an expression activity 10-40-fold less than the 35S promoter from Cauliflower mosaic virus. To delimit the minimal cis-acting elements necessary for vascular specificity of this promoter, a set of PCR deletion mutants of pRep(459::Rep) (pRep(459), pRep(324), pRep(203), pRep(145), pRep(132) and pRep(115)), were generated and used to transform tobacco plants. Transgenic tobacco plants belonging to all the pRep versions were blue stained in the vascular system except those from the pRep(115) version. The results described in this report demonstrate that the minimal sequences necessary for the pRep promoter activity are confined in a segment of 132 nts (located between the nts 2454 and 2585 of the ToMoTV DNA A) and that this promoter harbors those elements sufficient for vascular-specific expression.

Context fear conditioning inhibits panic-like behavior elicited by electrical stimulation of dorsal periaqueductal gray

Context fear conditioning has been widely used as an animal model of anxiety whereas electrical stimulation of the dorsal portion of the periaqueductal gray (DPAG) as a model of panic attack. The present study employed these two animal models in order to investigate the influence of anxiety in the occurrence of panic attack. Results indicated that animals exposed to contextual cues that were previously associated with electrical footshocks engaged in robust defensive freezing behavior and were less likely to display flight evoked by electrical stimulation of the DPAG when compared with control animals that were not exposed to the context fear conditioning procedure. These results indicate that activation of the brain mechanisms that underlie anxiety produces an inhibitory effect on panic attack.

Tomato mottle Taino virus pseudorecombines with PYMV but not with ToMoV: Implications for the delimitation of cis - and trans -acting replication specificity determinants

Over the last decade, the tomato production in Cuba has been affected by new whitefly-associated diseases. In addition to the well-documented presence of Tomato yellow leaf curl virus (TYLCV) along the island, the occurrence of bipartite begomoviruses has also been reported. One of them, tentatively named Tomato mottle Taino virus (ToMoTV), has now been cloned and characterized at the molecular level. Its genomic organization is similar to other bipartite geminiviruses. Phylogenetic analyses placed ToMoTV in a subcluster with other geminiviruses isolated in the Caribbean Basin: Tomato mottle virus (ToMoV), Bean dwarf mosaic virus, Abutilon mosaic virus, Sida golden mosaic virus and Potato yellow mosaic virus (PYMV). Biolistic inoculation of tobacco and tomato plants with cloned viral DNA showed that ToMoTV pseudorecombines with PYMV-GP as predicted by the identity of their iterative elements, whereas it does not show the same ability with ToMoV, even when their replication-associated proteins (Rep and REn) show the highest percentage of similarity. A comparative analysis of Rep proteins from begomoviruses that are able to produce viable reassortants suggests that some key elements for virus replication specificity are located in the first ten amino acids of this protein.

Molecular Characterization of Tobacco leaf rugose virus, a New Begomovirus Infecting Tobacco in Cuba

Tobacco (Nicotiana tabacum L.) is the main raw material for the cigar industry and one of the most important crops in Cuba comprising 49,654 ha. During the past 20 years, foliar rugosity and stunting symptoms have been observed in several tobacco producing areas. These symptoms were correlated with the presence of typical geminivirus nuclear inclusions and the transmission of the causal agent by whiteflies (Bemisia tabaci Genn) (1). To identify the suspect geminivirus, diseased leaf samples were collected in Havana province in 2000 and 2001. Sap extracts or leaf pieces were used to inoculate healthy tomato and tobacco plants by mechanical and graft inoculation procedures. Characteristic symptoms were reproduced in tobacco plants only by grafting (8 to 10 plants). DNA extracts from symptomatic plants were analyzed by Southern blot and polymerase chain reaction. The presence of a bipartite begomovirus was supported by the observation of hybridization signals (1.6 kb to 3 kb) at low stringency to probes derived from DNA-A and DNA-B of Taino tomato mottle virus. Furthermore, typical begomovirus amplicons of approximately 1.4 kb and 1.2 kb were amplified using the primer sets PAL1v1978-PAR1c715 and PAL1c1960-PAR1v722 (2), respectively. Amplicons were cloned, and their nucleotide sequences (nt) obtained from two clones each. Sequence for component A was assembled, and some fragments were compared with those for other begomoviruses using CLUSTAL W. For the CP gene (756 nt) (GenBank Accession No. AJ488768), the comparison revealed the highest percentages of nt identity with Sida golden mosaic virus from Florida (SiGMV-F, GenBank Accession No. AF049336) (86%), Tomato mottle virus (GenBank Accession No. L14460) (83.5%), and the yellow vein strain of Sida golden mosaic virus from Honduras (GenBank Accession No. Y11099) (83.3%). In addition, the percentages of nt identity obtained using the core region (a 540-nt fragment located between positions 147 and 687) of the CP gene from the tobacco virus were calculated. The best scores were as follows: SiGMV-F, 87.8%; Jatropha mosaic virus (JMV) from Puerto Rico (GenBank Accession No. AF058025), 86.9%; and Tomato rugose mosaic virus (GenBank Accession No. AF291705), 86.3%. Finally, comparisons of the common region (CR, 144 nt) revealed the highest values with JMV from Jamaica (JMV-JM) DNA-A and DNA-B (GenBank Accession Nos. AF324410 and AF324411; 89% and 91.1%, respectively). Interestingly, the CR analysis revealed the presence of the Ori-associated iterative motif GGGGT, which is the same in the CR of JMV-JM. Although the data suggest that the tobacco begomovirus is related to the JMV-JM isolate, it is a new species, and the name of Tobacco leaf rugose virus (TbLRV) is proposed. References: (1) S. Quintero and J. Santiesteban, Agrotec. Cuba 11(1), 1979. (2) M. R. Rojas et al. Plant Dis. 77:340, 1993.

Macroptilium yellow mosaic virus, a New Begomovirus Infecting Macroptilium lathyroides in Cuba

Macroptilium lathyroides (L) is a weed that is widely distributed in Cuba. Frequently, leaves show bright yellow mosaic symptoms, which suggest the incidence of a viral disease. Since begomovirus occurrence in Macroptilium lathyroides has been previously reported in other islands of the Caribbean (1,3), symptomatic plants from three distant places in Cuba (Havana, Villa Clara, and Camaguey), were collected and tested for the presence of begomoviruses. Plant DNA extracts were analyzed by Southern blot hybridization and polymerase chain reaction with two sets of degenerate primers (2). The presence of a bipartite begomovirus was evident through strong hybridization signals obtained with the DNA-A and DNA-B of Taino tomato mottle virus as probes at low stringency. Furthermore, 1.4-kb and 1.2-kb PCR amplified fragments were obtained with DNA-A degenerate primers, PAL1v1978-PAR1c715 and PAL1c1960-PAR1v722, respectively. Both PCR fragments from the samples from the three locations were cloned, and restriction fragment length polymorphism analysis of the 1.4-kb fragments were performed using PstI, EcoRI, HincII, XbaI and BglII. Restriction fragment patterns were the same for the three clones. The DNA-A sequence (GenBank Accession No. AJ344452) of the isolate from Villa Clara was compared with sequences available for other geminiviruses using CLUSTAL program. For the coat protein (CP) gene, the comparisons had the highest percentage of identity with various strains of Bean golden yellow mosaic virus (BGYMV, GenBank Accession Nos. AF173555, M91604, and L01635) (85 to 87% and 93 to 94%, nucleotide and amino acid sequences, respectively). For Rep gene (1,044 nt), the best percentages of identities were with BGYMV (81 to 82% and 80 to 82% nucleotide and amino acid sequences, respectively), Tomato leaf crumple virus (GenBank Accession No. AF101476) (78 and 81%, nucleotide and amino acid sequences, respectively), and Sida golden mosaic virus from Florida (GenBank Accession No. AF049336) (78 and 79%, nucleotide and amino acid sequences, respectively). Finally, the comparative analysis of the intergenic region (i.e. the common region plus the CP gene promoter) had the highest identity with BGYMV (56 to 55%) and Tomato severe rugose virus (GenBank Accession No. AY029750) (49%). Interestingly, this virus has in this region the three G-box elements that are characteristic of BGYMV but it differs in the Rep protein-binding iterative motif that is GGTGA instead of GGAGA, for BGYMV. These data indicate that this virus is a new begomovirus and the name of Macroptilium yellow mosaic virus (MaYMV) is proposed. References: (1) A. M. Idris et al. Plant Dis. 83:1071, 1999. (2) M. R. Rojas et al. Plant Dis. 77:340, 1993. (3) M. E. Roye et al. Plant Dis. 81:1251, 1997.

Chronic imipramine enhances 5-HT(1A) and 5-HT(2) receptors-mediated inhibition of panic-like behavior in the rat dorsal periaqueductal gray

Electrical stimulation of the dorsal periaqueductal gray (DPAG) has been used to induce panic-like behavior in rats. In the present study, we investigated the effect of chronic imipramine treatment on the sensitivity of different 5-HT receptor subtypes in inhibiting aversion induced by electrical stimulation of this brain area. For that, the effects of intra-DPAG administration of the endogenous agonist 5-HT (20 nmol), the 5-HT(1A) receptor agonist 8-OH-DPAT (8 nmol) and the 5-HT(2A/2C) receptor agonist DOI (16 nmol) were measured in female Wistar rats given either chronic injection of imipramine (15 mg/kg, 3 weeks, ip) or saline. The results showed that the three receptor agonists raised the threshold of aversive electrical stimulation in both groups of animals, but this antiaversive effect was significantly higher in rats treated with imipramine. Treatment with imipramine did not change the basal threshold of aversive electrical stimulation measured before intra-DPAG injection of the 5-HT agonists. The results suggest that sensitization of both 5-HT(1A) and 5-HT(2) receptors within the DPAG may be involved in the beneficial effect of imipramine in panic disorder (PD).

Cuban Isolate of Bean golden yellow mosaic virus is a Member of the Mesoamerican BGYMV Group

In Cuba, the emergence of bean golden mosaic was associated with high populations of Bemisia tabaci in common bean (Phaseolus vulgaris L.) plantings in the 1970s (1). During the last two decades, the disease has caused significant economic losses, forcing some growers to abandon bean production. In Holguín, one of the main bean producing provinces of the country, about 2,000 ha of beans were abandoned in 1991 due to the high incidence of this whitefly-transmitted virus. At that time, yield losses associated with this disease reached 90 to 100% in farmer's fields. In spite of various control measures, the disease affected 33, 28, and 6.5% of the total area planted in Cuba to common bean in 1990, 1992, and 1996, respectively. For this investigation, common bean leaves showing systemic yellowing symptoms were collected in fields located in the provinces of Havana, Matanzas, and Holguín during 1998-1999. Sap and total DNA leaf extracts were used to inoculate healthy bean plants by manual and biolistic procedures, respectively. Characteristic yellowing symptoms were more efficiently reproduced using a particle gun device than by manual inoculation (18/20 plants and 5/20 plants, respectively, for a Holguín virus isolate). DNA extracts were further analyzed by polymerase chain reaction using two degenerate primer sets: PAL1v1978-PAR1c715 and PAL1c1960-PAR1v722 (2). Fragments of approximately 1.4 and 1.2 kb were amplified and cloned. Restriction fragment length polymorphism analysis of the cloned 1.4-kb fragments was performed with BglII, HincII, SalI, EcoRI, PstI, and XbaI, indicating that selected isolates from the three Cuban provinces shared identical restriction patterns. The nucleotide sequence obtained from two clones of a virus isolate from Holguín, was compared to sequences available for other begomoviruses using BLAST. The Cuban isolate shared up to 94% nt sequence identity with various strains of Bean golden yellow mosaic virus (BGYMV) in the first 250 nt of the rep gene. For the common region (CR), scores were 93% for BGYMV-GA (Guatemala), 92% for BGYMV-MX (southern Mexico) and BGYMV-PR (Puerto Rico), and 91% for BGYMV-DR (Dominican Republic). The iterative sequence ATGGAG was identified in the CR of the Cuban BGYMV isolate, as reported for other BGYMV isolates. Finally, the Cuban begomovirus, hereafter referred to as BGYMV-CU, shared nt and aa sequence identities of 94 and 100%, respectively, with the coat protein gene of BGYMV-MX. We conclude that the begomovirus isolated from mosaic-affected common bean plants in the province of Holguín is a member of the Mesoamerican BGYMV group (3). References: (1) N. Blanco and C. Bencomo. Cienc. Agric. 2:39, 1978. (2) M. R. Rojas et al. Plant Dis. 77:340, 1993. (3) Morales and Anderson, Arch. Virol. 146:415, 2001.

Complementation of coat protein mutants of pepper huasteco geminivirus in transgenic tobacco plants

ABSTRACT The role of the pepper huasteco virus (PHV) coat protein (CP) gene during the infection was investigated in three different hosts by using mutations that produced truncated proteins and by complementation assays in transgenic plants. The infectivity analysis revealed that mutants that express truncated CP (CP7 and CP191) behave like the wild-type virus when inoculated onto pepper and Nicotiana benthamiana plants in terms of symptom expression and viral DNA movement. On the contrary, the CP7 mutant was unable to systemically infect tobacco plants, whereas only 10% of the plants inoculated with the CP191 mutant became infected. The CP7 mutant was complemented by coinoculating it with another geminivirus (taino tomato mottle virus). No complementation was observed in plants from nine transgenic tobacco lines expressing CP under the control of the cauliflower mosaic virus (CaMV) 35S promoter. However, 3 out of 10 lines expressing CP under the control of its own promoter (693 nucleotides) were able to complement the CP7 mutant. Interestingly, upon infection, the levels of CP mRNA in 693CP plants increased dramatically, probably due to transactivation of the CP promoter by the viral protein AC2.

Taino Tomato Mottle Virus, a New Bipartite Geminivirus from Cuba

Geminiviruses have become the most important virus group affecting tomatoes (Lycopersicon lycopersicum (L.) Karsten) in Cuba since they have been detected in all tomato-producing areas, causing serious losses. Recently, a whitefly-transmitted, monopartite geminivirus was detected in Cuba and identified as tomato yellow leaf curl virus-Israel (TYLCV-Is) (1). Samples collected from the main tomato-producing areas during the period 1995 to1996 were further analyzed by polymerase chain reaction (PCR) with degenerate primers (PAL1v1978 and PAR1c496) (2). Whereas in samples from most areas only TYLCV was detected, in some samples from the Havana area, two DNA fragments (approximately 1.4 and 1.1 kb) were amplified by PCR. The larger fragment was identified as part of the TYLCV-Is genome, confirming the previous report (1). The 1.1-kb fragment was cloned and its nucleotide sequence suggested that a new bipartite geminivirus was also present in those tomato samples. To clone the entire genome, tomato plants were inoculated by biolistics with DNA extract from field samples. After symptom expression, a viral DNA-enriched preparation from the inoculated tomatoes was independently digested with several restriction enzymes and the products were ligated into pZero plasmid (Invitrogen, San Diego, CA). Several clones in the 2.6-kb size range were characterized by restriction mapping and hybridization against component A and B heterologous probes. Two clones were selected as containing putative A and B components and their infectivity was tested by biolistic inoculation of tomato and pepper plants. The inoculated tomatoes developed a mild mottle in the younger leaves, whereas no symptoms were visible on the inoculated pepper plants. However, the presence of viral DNA was confirmed in both tomatoes and peppers by Southern blot hybridization analysis with A- and B-specific probes. Partial sequences of both components were obtained and their analysis showed that both components shared a 170-bases common region with a 95% identity. In addition, the nucleotide sequences of two open reading frames, one in each component (AC1 and BC1), were determined and compared with geminivirus sequences deposited in Gen-Bank. A dendogram generated with the CLUSTAL program and obtained with the AC1 and BC1 amino acid sequences, placed the new geminivirus in a cluster with tomato mottle virus (ToMoV; accession nos. L14460, L14461), Abutilon mosaic virus (AbMV; X15983, X15984), potato yellow mosaic virus (PYMV; D00940, D00941), and bean dwarf mosaic virus (BDMV; M88179, M88180). The percentages of identity obtained with the amino acid sequences were as follows. For AC1: ToMoV, 87%; PYMV, 79.5%; BDMV, 78.7%; and AbMV, 78%. For BC1 protein: BDMV, 92.8%; ToMoV, 89.1%; PYMV, 88.1%; and AbMV, 67.5%. In addition, the sequences were compared with partial nucleotide sequences (AC1, coat protein [CP], and common region) of a bipartite geminivirus affecting tomatoes in Jamaica (accession nos. U83855, U83854, and U83850). Interestingly, the common regions showed a higher percentage of identity (88%) than the CP and AC1 partial nucleotide sequences (86 and 74%, respectively). These data suggest that the virus reported here is a new geminivirus and the first bipartite geminivirus reported in Cuba. Thus, the name of Taino tomato mottle virus is proposed. (Taino refers to the name of the inhabitants of Cuba at the time of Columbus's arrival in the Caribbean). References: (1) P. L. Ramos et al. Plant Dis. 80:1208, 1996. (2) M. R. Rojas et al. Plant Dis. 77:340, 1993.

Ultrastructural, neurological, and glycosaminoglycan abnormalities in lowe's syndrome

The oculocerebrorenal syndrome (OCRS), Lowe's syndrome, is an X-linked, recessive disease characterized by mental retardation, congenital corneal abnormalities and cataracts, growth failure, rickets, osseous abnormalities, renal dysfunction with periodic acidosis, hypotonia, and areflexia. Ultrastructural studies of skin biopsy specimens in three individuals with the disorder (aged 17, 9, and 8 years) revealed cytoplasmic, membrane-bound, electron-lucent vacuoles and some electron-dense membranous inclusion bodies in fibroblasts and Schwann cells, as well as axonal degeneration and vascular changes. Computed tomographic scans evidenced brain atrophy. Urinary excretion of glycosaminoglycans (GAG) was four to five times greater than in normal controls. The predominant urinary GAG was a low-sulfated chondroitin-4-sulfate; chondroitin-6-sulfate and heparan sulfate excretion levels were normal. A tenfold increase in urinary GAG excretion was found in one patient with oculocerebrorenal syndrome during periods of behavioral agitation. These findings suggest that the clinical stigmata of oculocerebrorenal syndrome may be related to a defect in GAG metabolism.

Reduction of neuronal specific protein and some neurotransmitters in the infantile neuroaxonal dystrophy (INAD)

INAD with classical clinicopathological features was seen in three children of one family. They presented with a history of regression after the age of 1.5 years and died in mental institutions at the ages of 6, 7 and 9. Two of them had postmortem neuropathological studies, one had brain biopsy and one biochemical study. The following observations have been made; I. Histological--(1) some axonal loss with almost total absence of neurofilaments in dystrophic neurites and (2) marked degenerative changes and loss of synaptic vesicles; II. Biochemical--(1) the decrease of the neurofilament polypeptides by up to 75% and (2) a reduction of some neurotransmitter enzymes. The presence of intermitochondrial septate junctions. The neurofilament protein is specific to neurons and makes up a large percentage of their protein content. Neurofilaments have been implicated in several cellular functions such as intracellular transport and in the maintenance of cell structure. The decrease of neurofilament protein in our case is compatible with our morphological findings where we found decreased numbers of axons and an almost total absence of neurofilaments in the affected neurites.

Intermitochondrial septate structures in dystrophic axons

Intermitochondrial septate structures were found in the dystrophic axons of two cases of infantile neuroaxonal dystrophy. Septate structures were previously seen in some tumors (glioblastomas and Schwannomas) and several organs of vertebrates and invertebrates, but never in human central nervous system (CNS). The structures were studied by transmission and transmission tilt electron microscopy. A proposed model was constructed and X-rayed. Artist's depictions are shown and described. The intermitochondrial septate structures have a periodicity of 120 A which puts them within the range of those structures previously reported. It was found that our structures are not true junctions, but a complex interdigitation of the outer membranes of the involved mitochondria.