Dependence on host constituents controlling food acceptance by Manduca sexta larvae

The host range of Manduca sexta L. (Lepidoptera: Sphingidae) is restricted in nature to plants in the family Solanaceae. However, naive hatchling larvae often accept and continue their development on foliage from a wide spectrum of unrelated plants. In contrast, solanaceous-experienced larvae refuse to feed on other plants. Experiments were designed to explore the role of constituents of various plants in this behavioral phenomenon. Fourth instar larvae reared on solanaceous hosts: tomato (Lycopersicon esculentum Mill.), potato (Solanum tuberosum L.), or tobacco (Nicotiana tabacum L.), and the leguminous non-host cowpea (Vigna sinensis Savi), or on artificial diet based on wheat germ were tested for their acceptance or preference when offered a new diet in both choice and no-choice situations. Under no-choice conditions, acceptability of cowpea foliage was strongly affected by the larval dietary experience. Most larvae reared on solanaceous foliage did not feed, whereas those larvae reared on non-solanaceous food readily accepted cowpea. Moreover, solanaceous foliage, leaf discs and extracts were readily accepted by larvae regardless of their dietary experience. Larvae reared on any of the solanaceous plants strongly preferred cowpea discs that were treated with solanaceous extract, while larvae reared on non-solanaceous diets did not discriminate between treated and control discs. Assays of cowpea extracts as well as acceptance of cowpea discs treated with solanaceous extract indicated a lack of detectable deterrent in cowpea. Our results suggest that the mechanism for induced host specificity in M. sexta larvae involves development of a dependence on solanaceous chemical constituents. We argue that this dependence on host plant chemistry has adaptive significance.     

Ultrastructure of the galeal sensory complex in adults of the Colorado potato beetle, Leptinotarsa decemlineata

ABSTRACT. The structure of galeal sensilla of the Colorado potato beetle, Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae), is described using electron microscopical methods. Previous electro-physiological studies indicate that these sensilla respond to amino acids, sucrose and plant saps. One physiological type is particularly sensitive to L-alanine and gamma amino butyric acid (GABA).
Three morphologically different types of sensilla occur on the galeal tip. The more numerous apical pegs are not distinguishable from one another on the basis of external structure, although they differ physiologically. Five sensory cells are associated with most apical pegs. One apical peg, the α-sensillum, contains only four cells. All apical pegs have one cell with a tubular body. The remaining cells have unbranched dendrites and are associated with a single apical pore.
Apical hairs differ from the apical pegs by having double innervation. Within the hair shaft, a dendritic sheath is lacking and the sensillar sinus extends to the base of the hair. The function of this hair type is not known.
Numerous mechanosensory hairs which surround the other sensilla are singly innervated and contain a tubular body at the level of the outer dendritic segments.     

Immunolocalization of solanaceous SUT1 proteins in companion cells and xylem parenchyma: new perspectives for phloem loading and transport

Leaf sucrose (Suc) transporters are essential for phloem loading and long-distance partitioning of assimilates in plants that load their phloem from the apoplast. Suc loading into the phloem is indispensable for the generation of the osmotic potential difference that drives phloem bulk flow and is central for the long-distance movement of phloem sap compounds, including hormones and signaling molecules. In previous analyses, solanaceous SUT1 Suc transporters from tobacco (Nicotiana tabacum), potato (Solanum tuberosum), and tomato (Solanum lycopersicum) were immunolocalized in plasma membranes of enucleate sieve elements. Here, we present data that identify solanaceous SUT1 proteins with high specificity in phloem companion cells. Moreover, comparisons of SUT1 localization in the abaxial and adaxial phloem revealed higher levels of SUT1 protein in the abaxial phloem of all three solanaceous species, suggesting different physiological roles for these two types of phloem. Finally, SUT1 proteins were identified in files of xylem parenchyma cells, mainly in the bicollateral veins. Together, our data provide new insight into the role of SUT1 proteins in solanaceous species.     

Role of galeal sensilla in host recognition and feeding behaviour of the Colorado potato beetle

Abstract. Close-range interactions with plants and the early stages of feeding behaviour of adult Colorado potato beetles, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), were studied using beetles with and without various mouthpart sensilla. Representative host, potato (Solarium tuberosum) , and non-host, tomato (Lycopersicon esculentum) , leaves were treated very differently by beetles with and without their galeal or palpal sensilla. Galeal sensilla were particularly important for beetles interacting with these two plants. Compared with normal beetles, fewer beetles without galeae fed on potato leaves, and those that did feed spent more time assessing the plant and took more bites before feeding. On tomtato, more beetles without galeae fed, spent less time assessing the plant and took fewer bites before feeding. Beetles without galeae also had lower consumption rates on potato and higher consumption rates on tomato. Beetles were very reluctant to feed on tomato if the galeae were present so removal of maxillary sensilla was studied only on potato. Without the sensilla on the maxillary palpi only the time between first touch and first bite was affected (lengthened). The importance of galeal sensilla in host recognition by this species and the implications for chemosensory studies are discussed here and in a companion paper.     

Eggplant mosaic virus, and its relationship to Andean potato latent virus

Eggplant mosaic virus (EMV), obtained from Solanum melongena L. from Trinidad, is readily transmitted by inoculation of sap to several solanaceous and a few non-solanaceous plant species. Purified preparations of EMV contain isometric particles 30 nm in diameter, and with sedimentation co efficients of either 111 or 53 S. The particles have thirty-two major morphological subunits. EMV is closely serologically related to Andean potato latent virus and has a similar host range, but is more virulent. Also, whereas EMV accumulates fastest in Nicotiana clevelandii leaves at 20–24 °C, Andean potato latent virus accumulates fastest at 15 °C, and fails to attain a serologically detectable concentration at 24 °C. A few symptomatologically or serologically distinguishable strains of EMV were obtained. EMV has properties typical of viruses of the Andean potato latent subgroup of the turnip yellow mosaic group of viruses, and its present cryptogram is */*:*/*:S/S:S/Cl.     

Isolation of a lectin from the pericarp of potato (Solanum tuberosum) fruits.

A lectin has been isolated from potato (Solanum tuberosum) fruits by affinity adsorption on to glutaraldehyde-fixed erythrocytes and elution with oligomers of N-acetylglucosamine. The characteristics of the lectin resemble those of the potato tuber lectin and other closely related lectins from solanaceous plants.     

Specificity in the olfactory orientation of the Colorado beetle, Leptinotarsa decemlineata

Wind induces positive anemotactic responses of unfed newly-emerged female Colorado beetles. These responses are enhanced by the volatiles of several solanaceous species i.e. Solanum tuberosum, S. nigrum, S. luteum, S. dulcamara, S. lycopersicum, Nicotiana tabacum, Capsicum annuum and Petunia hybrida, and a non-solanaceous species, Tropaeolum majus. Brassica oleracea, B. pekinensis, Raphanus sativus and Phaseolus vulgaris are neutral in this respect. Unfed post-diapause Colorado beetles also react to the vapours of undamaged potted potato plants. It is concluded that the olfactory orientation will mainly lead the Colorado beetle towards solanaceous species. When contact results, further steps in host plant selection will occur.

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Zusammenfassung Wind induziert positive anemotaktische Reaktionen von frisch geschlüpften, noch nicht gefütterten Weibchen des Kartoffelkäfers. Diese Reaktionen werden verstärkt durch flüchtige Verbindungen verschiedener Solanaceen, nämlich Solanum tuberosum, S. nigrum, S. luteum, S. dulcamara, S. lycopersicum, Nicotiana tabacum, Capsicum annuum und Petunia hybrida und eine Nichtsolanacee, Tropaeolum majus. Brassica oleracea, B. pekinensis, Raphanus sativus und Phaseolus vulgaris waren in dieser Hinsicht neutral. Ungefütterte Postdiapause-Kartoffelkäfer reagieren ebenfalls auf flüchtige Verbindungen von ungeschädigten, getopften Kartoffelpflanzen. Es wird geschlossen, daß die geruchliche Orientierung den Kartoffelkäfer vorwiegend zu Solanaceen-Arten leitet. Sobald sich ein Kontakt ergibt, werden weitere Schritte in der Wirtspflanzenwahl erfolgen.

     

Low-temperature stress induces transient oscillations in sucrose metabolism in Solanum tuberosum

Exposure to low but nonfreezing temperatures induces the net breakdown of starch and the accumulation of sucrose, glucose and fructose in potato tuber tissue, a complex phenomenon known as low-temperature sweetening (LTS). When transferred to 4 degrees C storage, tissue sucrose levels in LTS-sensitive potato tubers (Solanum tuberosum cv. Norchip) did not change monotonically to a new steady state, but rather transiently oscillated about the trajectory to the new steady state. The dynamic patterns observed in sensitive tubers grown in 1993 and 1994 were qualitatively similar. Quantitatively, however, the transient oscillation had a period of 11.5 days in 1993, whereas a period of 80 days was observed in 1994. In contrast, the sucrose levels of the LTS-tolerant potato tubers (Solanum tuberosum seedling ND860-2) increased monotonically to a higher level upon exposure to low temperatures.     

Electrophysiological responses of galeal contact chemoreceptors of Apis mellifera to selected sugars and electrolytes

Using conventional electrophysiological methods, the galeal sensilla chaetica of the honey bee, Apis mellifera, responded linearly to the log of solute concentrations of sucrose, glucose, fructose, NaCl, KCl, and LiCl but not to CaCl₂ or MgCl₂, which failed to give consistent responses. These sensillae had much higher firing rates for sugar than salt solutions; their relative responses to lower concentrations being NaCl < KCl < LiCl ? fructose < glucose ? sucrose. At higher concentrations NaCl < LiCl < KCl ? glucose < fructose ? sucrose. Four different spike types were seen. The first type had the highest amplitude and resulted from sugar stimulation. The second type had a lower height and occurred in the first 30 sec of salt stimulation. A third type with the lowest height appeared with those of the second type after prolonged stimulation with KCl. A fourth type with a high amplitude resulted from mechanical stimulation. The sensilla adapted to sugar solutions linearly to the logarithm of time and non-linearly to the log of salt concentrations. Glucose-fructose mixed-sugar solution effected synergism of response while sucrose solutions caused inhibition when mixed with glucose and/or fructose. Responses of the sensilla to mechanical stimulation showed phasic-tonic characteristics. None of the sensilla tested responded to water.     

Purification of Potato Leaf Plasma Membrane Protein pp34, a Protein Phosphorylated in Response to Oligogalacturonide Signals for Defense and Development

A potato (Solanum tuberosum L.) plasma membrane protein called pp34, the only known example of a plasma membrane protein that is phosphorylated specifically in response to defined Oligogalacturonide signals in plants, has been purified to apparent homogeneity. Polyclonal antibodies raised in rabbits against the purified pp34 protein immunoprecipitated a single thiophosphorylated protein species from potato plasma membranes, as analyzed by two-dimensional denaturing electrophoresis and fluorography. The pp34 antibodies also recognized a single protein in tomato (Lycopersicon esculentum L.) membranes that is thiophosphorylated in response to Oligogalacturonide elicitors, as demonstrated by western blotting and specific immunoprecipitation. These experiments confirm the identity of the tomato membrane protein as a pp34 homolog and establish the high monospecificity of the pp34 antibodies. This will permit further investigation of the role of protein phosphorylation in oligouronide signaling for defensive genes in potato and tomato plants.     

Isolation and characterization of plant N-acetyl glucosaminyltransferase I (GntI) cDNA sequences. Functional analyses in the Arabidopsis cgl mutant and in antisense plants

We report on the isolation and characterization of full-length cDNA sequences coding for N-acetylglucosaminyltransferase I (GnTI) from potato (Solanum tuberosum L.), tobacco (Nicotiana tabacum L.), and Arabidopsis. The deduced polypeptide sequences show highest homology among the solanaceous species (93% identity between potato and tobacco compared with about 75% with Arabidopsis) but share only weak homology with human GnTI (35% identity). In contrast to the corresponding enzymes from animals, all plant GnTI sequences identified are characterized by a much shorter hydrophobic membrane anchor and contain one putative N-glycosylation site that is conserved in potato and tobacco, but differs in Arabidopsis. Southern-blot analyses revealed that GntI behaves as a single-copy gene. Northern-blot analyses showed that GntI-mRNA expression is largely constitutive. Arabidopsis cgl mutants deficient in GnTI activity also possess GntI mRNA, indicating that they result from point mutations. GntI-expression constructs were tested for the ability to relieve the GnTI block in protoplasts of the Arabidopsis cgl mutant and used to obtain transgenic potato and tobacco plants that display a substantial reduction of complex glycan patterns. The latter observation indicates that production of heterologous glycoproteins with little or no antigenic glycans can be achieved in whole plants, and not in just Arabidopsis, using antisense technology.     

A new plant virus from the high jungle of the Eastern Andes; Solanum apical leaf curling virus (SALCV)

A previously undescribed plant virus, Solanum apical leaf curling virus (SALCV), was found in cultivated potato and indigenous wild solanaceous plants in an area of high jungle near San Ramon, Peru. Symptoms in potato consisting of red, purple or pink discoloration, curling, crinkling and dwarfing of apical leaves develop soon after infection. Symptoms from tuber-borne infection may also include dwarfing and stunting, dormancy may be prolonged and sprouts may be filiform producing small plants with very thin stems. The virus is transmissible by grafting, but was not transmitted through seed, by aphids or leafhoppers tested, nor by mechanical inoculation of sap. Infected Datura tatula and D. stramonium, the most useful indicator hosts, developed yellowing of the small veins of newly formed leaves followed by distortion, dwarfing, and cupping of subsequently formed leaves. Tomato, Solanum nigrum, Nicandra physalodes and Nicotiana benthamiana were also infected experimentally. N. physalodes, Solanum basendopogon, D. tatula and Physalis peruviana were naturally infected in the field. Antiserum produced in rabbits was suitable for ELISA which detected SALCV in a range of graft-inoculated and naturally infected plants. Most virus particles in purified preparations and those trapped on antiserum sensitised grids treated with infective sap were c. 52 times 17 nm and consisted of three quasi-isometric units in a straight chain. This particle morphology although novel, suggests possible affinities with geminiviruses.     

11-hydroperoxyeicosatetraenoic acid is the major dioxygenation product of lipoxygenase isolated from hairy root cultures of Solanum tuberosum.

The profile of primary dioxygenation products of arachidonic acid catalyzed by lipoxygenase isolated from hairy root cultures of Solanum tuberosum treated with a fungal elicitor was compared to that obtained for the enzyme from potato tubers. 11-Hydroperoxyeicosatetraenoic acid (11-HPETE) was the most abundant dioxygenation product formed followed by 8- and 5-HPETEs in the decreasing order of abundance. In contrast, 5-HPETE is the predominant oxidation product of lipoxygenase from potato tubers. Differences in the defense requirements of storage tuber as compared to roots may be the basis of the differences in regio-specificity demonstrated in this work.     

Resistance to potato virus Y and potato virus X in Solanurn brevidens

Although Solanum brevidens could be infected with potato virus X (PVX), potato virus Y⁰ (PVY⁰) and PVY^N, no symptoms of infection were apparent and tests by double antibody sandwich ELISA, electron microscopy and sap transmission to local lesion test plants indicated that the titres of PVX were less than a tenth of those of PVY⁰ and PVY^N were less than a hundredth of those in infected plants of PDH40, a susceptible dihaploid clone of S. tuberosum cv. Pentland Crown. Furthermore, PVY⁰- and PVY^N- infected leaves of S. brevidens were a poor source of inoculum in aphid transmission tests. The possibility of a common mechanism and genetic basis of resistance to PVY, PVX and potato leaf roll virus in S. brevidens is discussed.     

Phytochrome B mediates the photoperiodic control of tuber formation in potato

To determine whether phytochrome B is involved in the response of potato plants to photoperiod, a potato PHYB cDNA fragment was inserted in the antisense orientation behind the 35S CaMV promoter in Bin19 and this construct was transformed into Solanum tuberosum ssp. andigena plants which normally require short days for tuberization. Two independent transformants were obtained that had much lower levels of PHYB mRNA and protein, and which exhibited phenotypes characteristic of phyB mutants, for example, elongated stems and decreased chlorophyll content. The level of phyA, and of several phytochrome A-controlled responses, was unaffected in these plants. The photoperiodic control of tuberization in these antisense PHYB plants was abolished, the plants tuberizing in short day, long day, or short day plus night break conditions. This result shows that phytochrome B is required for the photoperiodic control of tuberization in potato ( Solanum tuberosum ssp. andigena ) and that it regulates this developmental process by preventing tuber formation in non-inductive photoperiods rather than by promoting tuberization in inductive photoperiods.     

Race nonspecific resistance for potato late blight

The late blight fungus (Phytophthora infestans) rots susceptible species of potato plants. None of the major varieties of potato (Solanum tuberosum) grown in the USA is resistant to US-8, the most prevalent genotype of the fungus. Now, Junqi Song, James Bradeen and colleagues have cloned the RB gene from the wild diploid potato species, Solanum bulbocastanum, using a map-based approach in combination with long-range PCR. Transgenic plants containing the gene, normally fully susceptible, displayed broad-spectrum late blight resistance.     

Evolutionary meta-analysis of solanaceous resistance gene and solanum resistance gene analog sequences and a practical framework for cross-species comparisons

Cross-species comparative genomics approaches have been employed to map and clone many important disease resistance (R) genes from Solanum species-especially wild relatives of potato and tomato. These efforts will increase with the recent release of potato genome sequence and the impending release of tomato genome sequence. Most R genes belong to the prominent nucleotide binding site-leucine rich repeat (NBS-LRR) class and conserved NBS-LRR protein motifs enable survey of the R gene space of a plant genome by generation of resistance gene analogs (RGA), polymerase chain reaction fragments derived from R genes. We generated a collection of 97 RGA from the disease-resistant wild potato S. bulbocastanum, complementing smaller collections from other Solanum species. To further comparative genomics approaches, we combined all known Solanum RGA and cloned solanaceous NBS-LRR gene sequences, nearly 800 sequences in total, into a single meta-analysis. We defined R gene diversity bins that reflect both evolutionary relationships and DNA cross-hybridization results. The resulting framework is amendable and expandable, providing the research community with a common vocabulary for present and future study of R gene lineages. Through a series of sequence and hybridization experiments, we demonstrate that all tested R gene lineages are of ancient origin, are shared between Solanum species, and can be successfully accessed via comparative genomics approaches.