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PubMed2004

Early responses of resistant and susceptible potato roots during invasion by the potato cyst nematode Globodera rostochiensis.

Signals from roots of resistant (cv. Maris Piper) and susceptible (cv. Désirée) potato cultivars during invasion by second stage juveniles (J2s) of the potato cyst nematode, Globodera rostochiensis, were investigated. Novel experimental chambers enabled the recording of electrophysiological responses from roots during nematode invasion. The root cell membrane potentials were maintained throughout the 3 d required to assess invasion and feeding site development. The steady-state resting membrane potentials of Désirée were more negative than those of Maris Piper on day 1, but the reverse on day 3. After 5 d there was no difference between the two cultivars. Intracellular microelectrodes detected marked spike activity in roots after the application of J2s and there were distinct and reproducible differences between the two cultivars, with the response from Désirée being much greater than that from Maris Piper. The responses to mechanical stimulation of roots by blunt micropipettes and sharp electrodes were consistent and similar in both cultivars to the responses in Maris Piper obtained after nematode invasion, but could not account for the marked response found in Désirée. Exogenous application of exoenzymes, used to mimic nematode chemical secretions, resulted in a distinct depolarization pattern that, although similar in both cultivars, was different from patterns obtained during nematode invasion or mechanical stimulation. The pH of homogenates prepared from roots of both cultivars was measured and a Ca2+ channel blocker was used to assess the role of Ca2+ in nematode invasion. The results indicated a role for Ca2+ in the signalling events that occur during nematode invasion.

Animals↗

PubMed1987

Organ-specific and dosage-dependent expression of a leaf/stem specific gene from potato after tagging and transfer into potato and tobacco plants.

ST-LS1, a single copy gene from potato displaying a leaf/stem specific gene expression, was tagged by an exon modification and introduced into both potato and tobacco cells using Agrobacterium vectors. After regeneration of whole plants, the expression of the tagged gene was analyzed with respect to its organ specificity and compared to the expression of the corresponding resident gene. The expression of the transferred gene in transgenic plants closely followed the expression of the resident gene. No marked influence of the plant species serving as host was observed. The level of expression of the introduced gene varied by a factor of at least 100 in independent transformants when normalized to the expression of the resident gene. Southern analysis performed on the transformed plants indicated a correlation between copy number of the introduced gene and its expression level. The activity of the tagged gene as well as of the resident gene was significantly inhibited by treatment of the transgenic plants with the herbicide norfluorazon, indicating that this gene activity is dependent on the presence of functional chloroplasts in the leaves.

DNA, Recombinant↗

PubMed1995

Only one of four possible secondary structures of the central conserved region of potato spindle tuber viroid is a substrate for processing in a potato nuclear extract.

The influence of RNA secondary structure on the substrate activity of a longer-than-unit length transcript for processing to circular viroids was studied in a nuclear extract from potato suspension cells. The nuclear extract was prepared according to a modified procedure for a plant transcription extract. The transcript of the potato spindle tuber viroid (PSTVd) consists of a monomeric molecule with 17 additional nucleotides, thus doubling most of the central conserved region of viroids of the PSTVd-class. The transcript can assume four different secondary structures, which either co-exist as conformers in solution or can be kept as metastable structures after different treatments by temperature and/or ionic strength. The structures were analysed by thermodynamic calculations and temperature-gradient gel electrophoresis and were confirmed by oligonucleotide mapping. Only the so-called extended middle structure was processed to exact viroid circles. In this structure the 5'- and 3'-ends are branching out from the rod-like viroid structure at the loop starting with nucleotide 87. The other structures were processed only if they could be rearranged into the active structure.

Base Sequence↗

PubMedDate not supplied

Enhancement of resistance to potato leafroll virus multiplication in potato by combining the effects of host genes and transgenes.

Four potato clones with host gene-mediated resistance to potato leafroll virus (PLRV) multiplication were transformed with the PLRV coat protein (CP) gene. Plants of lines expressing high levels of transcript were highly resistant to PLRV multiplication; virus concentration was only 20-40 ng/g of leaf, which is approximately 1% of the concentration reached in susceptible cultivars. The effects of the transgenic and host-derived resistance genes appear to be additive.

Capsid↗

PubMed2000

Recessive and dominant genes interfere with the vascular transport of Potato virus A in diploid potatoes.

Resistance to Potato virus A (PVA) was examined in a diploid cross involving Solanum tuberosum subsp. andigena as a resistance source. Hypersensitive resistance (HR) to PVA cosegregated with extreme resistance (ER) to Potato virus Y conferred by the dominant gene Ry(adg) on chromosome XI. Hence, HR to PVA was controlled by a novel, dominant resistance gene closely linked to Ry(adg), or Ry(adg) recognized both viruses but conferred a different type of resistance to each virus. The HR prevented systemic infection with PVA following mechanical inoculation but not following graft inoculation. Another, recessive gene, ra, that may be linked or even allelic with Ry(adg) fully blocked vascular transport of PVA in graft-inoculated plants. Hence, a possibility exists that the genes for the three types of resistance to potyviruses may reside at the same, resistance gene-rich chromosome region syntenic in solanaceous species and might be related. The gene ra acted against all of the three PVA strains tested and, therefore, the avirulence determinants could not be mapped. However, also, PVA strain-specific resistance was found in the progeny. It was overcome by mutations introduced into the viral genome-linked protein and the helper component proteinase and/or the coat protein.

Biological Transport↗

PubMed1997

Expression of the coat protein of potato virus X from a dicistronic mRNA in transgenic potato plants.

Transgenic potato plants were generated which express a dicistronic mRNA corresponding to the 8 kDa protein and coat protein (CP) genes of potato virus X (PVX). Northern blot analysis of RNA isolated from these plants indicated that both the 8 kDa protein and the CP are translated from this dicistronic mRNA. Expression of both of these proteins in transgenic plants was demonstrated by Western blot analysis, and suggests that translation of CP takes place either by initiation by internal entry of ribosomes or by a termination/reinitiation mechanism. CP was detected in protoplasts electroporated with RNA transcripts of the dicistronic construct in the presence or absence of a stable hairpin structure at the 5' terminus, suggesting that the former model is more likely. Similar results were obtained when a DNA fragment containing the PVX CP leader sequence was placed between two reporter genes in the transient assay system. These results suggest that potexvirus CP expression may take place from the genomic RNA as well as from the subgenomic RNA.

Base Sequence↗

PubMed2006

Rhizosphere bacteria affected by transgenic potatoes with antibacterial activities compared with the effects of soil, wild-type potatoes, vegetation stage and pathogen exposure.

A greenhouse experiment was performed to analyze a potential effect of genetically modified potatoes expressing antibacterial compounds (attacin/cecropin, T4 lysozyme) and their nearly isogenic, nontransformed parental wild types on rhizosphere bacterial communities. To compare plant transformation-related variations with commonly accepted impacts caused by altered environmental conditions, potatoes were cultivated under different environmental conditions, for example using contrasting soil types. Further, plants were challenged with the blackleg pathogen Erwinia carotovora ssp. atroseptica. Rhizosphere soil samples were obtained at the stem elongation and early flowering stages. The activities of various extracellular rhizosphere enzymes involved in the C-, P- and N-nutrient cycles were determined as the rates of fluorescence of enzymatically hydrolyzed substrates containing the highly fluorescent compounds 4-methylumbelliferone or 7-amino-4-methyl coumarin. The structural diversity of the bacterial communities was assessed by 16S rRNA-based terminal restriction fragment length polymorphism analysis, and 16S rRNA gene clone libraries were established for the flowering conventional and T4 lysozyme-expressing Desirée lines grown on the chernozem soil, each line treated with and without E. carotovora ssp. atroseptica. Both genetic transformation events induced a differentiation in the activity rates and structures of associated bacterial communities. In general, T4 lysozyme had a stronger effect than attacin/cecropin. In comparison with the other factors, the impact of the genetic modification was only transient and minor, or comparable to the dominant variations caused by soil type, plant genotype, vegetation stage and pathogen exposure.

Anti-Bacterial Agents↗

PubMed2001

Resistant potato selections contain leptine and inhibit development of the Colorado potato beetle (Coleoptera: Chrysomelidae).

We recently described a new source of host-plant resistance to the Colorado potato beetle, Leptinotarsa decemlineata (Say), in a tetraploid potato (Solanum tuberosum L.) selection, ND2858-1. This genotype, and selected backcross progeny, had little damage while check cultivars were defoliated in open-choice field assays. To further characterize the observed deterrence, we determined foliar glycoalkaloids and conducted no-choice assays with ND2858-1 backcross progeny genotypes (ND4382-n). Development of neonate L. decemlineata in detached leaf assays on resistant progeny genotypes was delayed and larval weight gain after 4 d was inhibited by 75% relative to larval development and weight gain on susceptible genotypes. Inhibition of larval development in detached leaf assays with the selected progeny genotypes was equivalent to that of high-leptine genotypes of S. chacoense Bitter. Foliar glycoalkaloids of resistant genotypes included low levels of leptines I and II. The unlikely nature of this cross and the presence of leptine in this and resistant progeny selections cast doubt on the recorded pedigree. Molecular analyses were conducted by restriction fragment-length polymorphism and amplified fragment-length polymorphisms. Both methods established a high degree of relatedness to S. tuberososum and S. chacoense but not to S. fendleri. We conclude that ND2858-1 did not originate from a cross with S. fendleri, but is likely derived from S. chacoense. Oviposition and larval survival were reduced when adult L. decemlineata were placed in cages with resistant genotypes; an effect that was enhanced by inclusion of Perillus bioculatus F. Therefore, the nonpreference previously observed in open-choice field defoliation assays is also associated with antibiotic effects on L. decemlineata. The resistance may be caused by leptines, but is greater than would be expected by the leptine content. This source of host plant resistance could be a cost-effective management strategy, especially if combined with other resistance mechanisms or compatible control measures to delay development of resistance in the target insects.

Animals↗

PubMed1976

Comparison of antibiotic-amended potato dextrose agar and acidified potato dextrose agar as growth substrates for fungi.

Fifteen fungal species, all isolated from food, were compared for their growth abilities on potato dextrose agar acidified to pH 3.5, and on nonacidified potato dextrose agar amended with 40 ppm chlortetracycline hydrochloride. Comparisons were made at 16, 21, 26, 32, and 37 degrees C. Of the 15 species, only Penicillium expansum exhibited better growth on the acidified medium than on the nonacidified antibiotic medium, while 9 species grew better on the nonacidified antibiotic medium. Five species grew equally well on either medium.

Agar↗

PubMed1981

Translation in vitro of ribonucleic acids from potato virus X, potato virus M and white clover mosaic virus.

Ribonucleic acids from three plant viruses: potato virus X (PVX), potato virus M (PVM) and white clover mosaic virus (WClMV) have been purified and used as messengers in a wheat germ cell-free system. It was demonstrated that each of these viruses contained heavy genomic RNA species of mol. wt. about 2 x 10(6), which appeared to be very efficient templates for protein synthesis in vitro. The synthesis of high-molecular-weight polypeptides: 180 x 10(3), 190 x 10(3) and 170 x 10(3) was directed by PVX, PVM and WClMV RNAs, respectively. None of the polypeptides directed by any of the RNAs studied corresponded to the coat proteins.

Molecular Weight↗

PubMed2001

Volatile flavour components of baked potato flesh. A comparison of eleven potato cultivars.

Tubers of eleven cultivars of potato were baked and the flavour compounds from the flesh were isolated by headspace adsorption onto Tenax and analysed by gas chromatography-mass spectrometry (GC-MS). Lipid degradation and the Maillard reaction were the main sources of flavour compounds, accounting for 22-69% and 28-77%, respectively, of the total yields. Various sulfur compounds, methoxypyrazines and terpenes were also identified at lower levels. Relative aroma impact values (RAVs) were calculated by dividing compound yields by the odour threshold value. Compounds contributing most to aroma (RAV > 10,000 in at least one cultivar) were 2-isobutyl-3-methoxypyrazine, 2-isopropyl-3-methoxypyrazine, beta-damascenone, dimethyl trisulfide, decanal and 3-methylbutanal. The observed differences in yields and RAVs for compounds among cultivars would be expected to result in differences in perceived flavour.

Cooking↗

PubMed2006

The effect of insecticide application sequences on the control and insecticide resistance status of the peach-potato aphid, Myzus persicae (Hemiptera:Aphididae), on field crops of potato.

Experiments were done on commercial potato crops in the UK to investigate the effect of different insecticide sequences on the control and insecticide resistance status of Myzus persicae (Sulzer). The work was done to provide field validation of similar laboratory studies done in 'field simulators'. To ensure adequate aphid populations and to influence the initial resistance status of the aphid population, cultured M. persicae from a clone of known resistance status (esterase R1, kdr heterozygote, non-MACE (modified acetylcholinesterase)) were inoculated into both experiments. Two-spray programmes starting with lambda-cyhalothrin (a pyrethroid insecticide) gave poor control in comparison with programmes starting with pirimicarb (a carbamate insecticide) or pirimicarb-containing mixtures. This concurred closely with the results obtained from single applications in field simulator studies. Treatment sequences containing pymetrozine (a pyridine azomethine insecticide) were also effective, though slower-acting. This again concurs with field simulator studies. The proportions of aphids carrying different resistance mechanisms were largely unaffected by treatment in these experiments. The implications of these results for field control strategies are discussed.

Analysis of Variance↗

PubMed1983

Oligomeric forms of potato spindle tuber viroid (PSTV) and of its complementary RNA are present in nuclei isolated from viroid-infected potato cells.

Different oligomeric forms of PSTV are detected in nuclei isolated from PSTV-infected potato cells by means of molecular hybridization, using as probes synthetic oligodeoxyribonucleotides with sequence specificity for (+)PSTV and for (-)PSTV. In addition to several species of longer-than-unit-length (-)PSTV molecules, two oligomeric forms of (+)PSTV are detected, which correspond in size to RNA strands of approximately two and three times viroid unit-length. They must be considered as the precursors of the circular and linear (+)PSTV monomers accumulating in the cell nucleus.

Base Sequence↗

PubMed1977

Studies on enzymic browning of potatoes (Solanum tuberosum). III. Kinetics of potato phenoloxidase (EC 1.14.18.1 monophenol, dihydroxyphenylalanine: oxygen-oxidoreductase).

From initial velocity studies a sequential mechanism for the reactions catalysed by phenoloxidase from potatoes is indicated. The data are in accordance with an ordered addition of oxygen and phenolic substrate to the enzyme, with oxygen being the first substrate bound at thermodynamic equilibrium. The Michaelis constants for L-tyrosine, L-dopa, and chlorogenic acid are 1.4 X 10(-3), 3.3 X 10(-4), and 1.4 X 10(-4) mol/l, respectively. The dissociation constant for the enzyme-oxygen complex is about 10(-3) mol/l. In the presence of chlorogenic acid no lag phase occurs in the course of L-tyrosine oxidation. With increasing amounts of chlorogenic acid the tyrosinase activity goes through a maximum. The significance of these findings for the in vivo action of the enzyme is discussed.

Catalysis↗

PubMed1990

Detection of potato spindle tuber viroid (PSTV) in dormant potato tubers by concatameric cDNA probe.

The 32P-labelled concatameric insert cut out from a plasmid pSPAv6.2(+), containing 6.2 copies of a full-length PSTV, was used to detect PSTV in dormant potato tubers by dot-blot hybridisation assay. The concatameric insert probe was 4 times more sensitive than the monomeric one. This allowed the detection of 0.5 pg of viroid RNA. The sensitivity makes th eoligomeric cDNA probe a useful alternative to cDNA probes.

DNA Probes↗

PubMed1997

Hydroponic potato production on nutrients derived from anaerobically-processed potato plant residues.

Bioregenerative methods are being developed for recycling plant minerals from harvested inedible biomass as part of NASA's Advanced Life Support (ALS) research. Anaerobic processing produces secondary metabolites, a food source for yeast production, while providing a source of water soluble nutrients for plant growth. Since NH4-N is the nitrogen product, processing the effluent through a nitrification reactor was used to convert this to NO3-N, a more acceptable form for plants. Potato (Solanum tuberosum L.) cv. Norland plants were used to test the effects of anaerobically-produced effluent after processing through a yeast reactor or nitrification reactor. These treatments were compared to a mixed-N treatment (75:25, NO3:NH4) or a NO3-N control, both containing only reagent-grade salts. Plant growth and tuber yields were greatest in the NO3-N control and yeast reactor effluent treatments, which is noteworthy, considering the yeast reactor treatment had high organic loading in the nutrient solution and concomitant microbial activity.

Anaerobiosis↗

PubMed2003

Tritrophic interactions between transgenic potato expressing snowdrop lectin (GNA), an aphid pest (peach-potato aphid; Myzus persicae (Sulz.) and a beneficial predator (2-spot ladybird; Adalia bipunctata L.).

Tritrophic interactions between transgenic potato expressing the insecticidal lectin from snowdrop (Galanthus nivalis agglutinin; GNA), an aphid pest, Myzus persicae (Sulz.), and a beneficial predator, the 2-spot ladybird (Adalia bipunctata L.) were investigated. Clonal plants expressing GNA at 0.1-0.2% total soluble protein in leaves were used. No significant effects on development and survival of ladybird larvae fed on aphids from these transgenic plants were observed, with larval survival in the experimental group being 90% compared to 89% for controls. There were also no effects on subsequent female or male longevity. Female fecundity was also investigated. Although no significant differences (p > 0.05) were observed in egg production between control and experimental groups, a 10%, reduction (p < 0.01) in egg viability (determined by % hatch) occurred in ladybirds fed aphids reared on transgenic plants. Additional studies were carried out using aphids fed on artificial diet containing GNA, to deliver quantified levels of the protein to ladybird adults. GNA had no deleterious effects upon adult longevity, but resulted in a consistent trend for improved fecundity. Egg production was increased by up to 70% and egg viability also increased significantly. The results suggest that GNA is not deleterious to ladybirds. Results from these studies highlight the need to discriminate between direct and indirect effects when studying tritrophic interactions between plants/pests/natural enemies. Furthermore, it emphasises the importance of demonstrating 'cause and effect'.

Animals↗

PubMed2003

Potato virus Y NIa protease activity is not sufficient for elicitation of Ry-mediated disease resistance in potato.

Ry confers extreme resistance (ER) to all strains of potato virus Y (PVY). In previous work, we have shown that the protease domain of the nuclear inclusion a protease (NIaPro) from PVY is the elicitor of the Ry-mediated resistance and that integrity of the protease active site is required for the elicitation of the resistance response. Two possibilities arise from these results: first, the structure of the active protease has elicitor activity; second, NIa-mediated proteolysis is required to elicit the resistance response. To resolve these possibilities, the NIaPro from PVY was randomly mutagenised and the clones obtained were screened for elicitation of cell death as an indicator of resistance and proteolytic activity. We did not find any mutants that had retained the ability to elicit cell death but had lost protease activity, as measured by processing of the NIa cleavage site in the viral genome. This was consistent with the idea that protease activity is necessary for elicitor activity. However, protease activity was not sufficient because we found three elicitor-defective mutants in which there was a high level of protease activity in this assay.

Base Sequence↗