Gynura Aurantiaca Research Articles

Diversity of weeds on bamboo seedling’s media in Bali Botanical Garden

In general, weeds are obnoxious plants that live in an unwanted place and have negative impact towards human, other plants and the environment. The research aimed to know the weeds species composition that composed in the growing media of Guadua chacoensis bamboo. The research was conducted in an open space of the Bali Botanical Garden nursery at an altitude of 1200 m a.s.l. The research was conducted for 3 months from July to October 2004. Results showed that as many as 28 species of weeds were found which included in 15 families. Weeds species compositions in each of the type of growing media are significantly different. In the soil media weeds comprises of Amaranthus blitum L. (Amaranthaceae) and Galinsoga parviflora Cav. (Asteraceae), in the humus media the weeds are Cyperus rotundus L. (Cyperaceae) and Gynura aurantiaca (Bl.) DC. (Asteraceae), in the cow’s feces media, the weeds is Amaranthus blitum L. (Amaranthaceae) and laslty in the KOMPENIT fertilizer media the weeds comprises of Eleusine indica (L.) Gaertn.(Poaceae), Drymaria cordata (L.) Willd. ex R. & S. (Caryophyllaceae ) and Cyperus rotundus L. (Cyperaceae).

Regeneration of Gynura aurantiaca ‘Purple Passion’ via indirect shoot organogenesis

Gynura aurantiaca (Blume) DC ‘Purple Passion’ is an important ornamental foliage plant. Its purple-colored leaves contain acylated anthocyanins which have potential to be natural food colorants. Production of this crop requires healthy and uniform starting materials or propagules. This study developed simple and efficient protocols for regenerating ‘Purple Passion’ through indirect shoot organogenesis. Reddish, purple colored callus was induced from leaf explants cultured on MS basal medium supplemented with 2.0 mg L−1 TDZ or 2.0 mg L−1 BA in combination with 0.5 mg L−1 2,4-D. Callus pieces (5 mm3) were cultured on the same medium with the same concentrations of TDZ or BA with 2,4-D for inducing adventitious shoots. More than 25 adventitious shoots were produced per callus piece. Microcuttings derived from the shoots were easily rooted in vitro, and rooted cuttings were transplanted into a peat-based substrate and grown in a shaded greenhouse. Plants grew vigorously in the shaded greenhouse with a high survival rate. They were morphologically stable without any phenotypic variation. Chromosome numbers of randomly selected regenerated plants and stock plants were the same with 2n = 40. Additionally, reddish, purple callus had significantly higher content of anthocyanins than leaves of regenerated plants grown in the shaded greenhouse, suggesting that callus induced through the established protocols could be used to produce acylated anthocyanins as natural food colorants through bioreactor culture.

In vitro system for studying interactions between Citrus exocortis viroid and Gynura aurantiaca (Blume) DC. metabolism and growing conditions

Citrus exocortis viroid (CEVd) is an economically important plant pathogen, which infects a broad range of hosts. In order to investigate complex interactions among viroid, host-growing conditions, and plant secondary metabolism, we setup an in vitro system for the cultivation of CEVd-infected and viroid-free Gynura aurantiaca (Blume) DC. shoots. Both basal Murashige and Skoog (MS) medium and MS medium supplemented with cytokinines supported the growth of shoots, but viroid-free shoots performed better than infected ones. The addition of cytokinines induced an increase in the concentration of purple-reddish pigment, cyanidin tetra-glucoside (GAA), which did not depend on the presence of viroid. The differences in single strand conformation polymorphism patterns between CEVd sequence variants obtained from plants grown on medium supplemented with cytokinines and those obtained from plants grown on basal MS medium or in the greenhouse, indicated that cytokinines may influence not only the plant metabolism, but also the viroid population structure.

Two nucleotide positions in the Citrus exocortis viroid RNA associated with symptom expression in Etrog citron but not in experimental herbaceous hosts

Citrus exocortis viroid (CEVd) is the causal agent of exocortis disease of citrus. CEVd has a wide host range that includes woody and herbaceous species. A new CEVd strain (CEVd(COL)), phylogenetically clustering with CEVd variants of Class A inducing severe symptoms in tomato, was identified in Colombia and shown to induce only extremely mild symptoms in Etrog citron indicator plants. Using site-directed mutagenesis, two nucleotide substitutions (314A → G and 315U → A) in the lower strand of the P domain of the predicted CEVd(COL) secondary structure resulted in a severe artificial CEVd(MCOL) variant. Conversely, two nucleotide exchanges (314G → A and 315A → U) in the same region of the severe variant CEVd(E-117) resulted in a symptomless artificial CEVd(ME-117) variant. Infectivity assays conducted with the natural and mutated variants showed that all induced severe symptoms in Gynura aurantiaca, tomato and chrysanthemum. This is the first report of the identification of pathogenic determinants of CEVd in citrus, and shows that these pathogenicity determinants are host dependent.

Cultural Guidelines for Commercial Production of Purple Passion Plant (Gynura aurantiaca)

ENH-1079, a 4-page illustrated fact sheet by Jianjun Chen and Richard J. Henny, provides guidelines for commercial production of this colorful, velvety foliage plant: propagation, cultural requirements, common problems, and recommendations for interior use. Includes references. Published by the UF Department of Environmental Horticulture, October 2007. ENH1079/EP346: Cultural Guidelines for Commercial Production of Purple Passion Plant (Gynura aurantiaca) (ufl.edu)

Molecular characterization of CEVd strains that induce different phenotypes in Gynura aurantiaca: structure-pathogenicity relationships

Two Citrus exocortis viroid isolates (CEVd-s and CEVd-129) that induce severe and mild symptoms in Gynura aurantiaca, respectively, have been characterized. They present nucleotide sequences in the pathogenicity motifs P(L), C and P(R) similar to those of "Class A" and "Class B". Infectivity and symptom expression in G. aurantica and tomato were evaluated with a selection of sequence variants recovered from both isolates. As expected, the two variants selected from CEVd-s induced severe symptoms. The variants selected from CEVd-129 induced mild symptoms, except one of them, named MJ, that presented an unusual genotype and induced severe symptoms in G. aurantiaca. The biological properties of MJ show that the two nucleotide changes of the C domain normally associated with the P(L) and P(R) motifs of "Class B" strains are not implicated in symptom expression. The relationship between "Class A" and "Class B" strains with the symptoms induced in clementine trees grafted on trifoliate orange is discussed.

RNA silencing as related to viroid induced symptom expression.

Evidence of post-transcriptional gene silencing (PTGS) in avocado infected by Avocado sunblotch viroid (ASBVd), the type species of family Avsunviroidae, was suggested by detection of ASBVd-specific 22-nucleotide RNAs. PTGS was observed in infected bleached and variegated symptomatic tissues as well as symptomless carrier foliar sources and fruit with typical sunblotch disease lesions. Tissues with the different symptom expressions, characterized by the presence of different predominant ASBVd variants, were found to induce PTGS at differential levels. Detection of the PTGS-associated small interfering RNAs (siRNAs) as well as relative concentration was also related to viroid titer. PTGS induced in Gynura aurantiaca infected with two closely-related variants of Citrus exocortis viroid, a member of family Pospiviroidae, was not directly related to viroid titer with initiation of symptoms.

CEVd-Induced Symptom Modification as a Response to a Host-Specific Temperature-Sensitive Reaction

Natural selection of two new variants of citrus exocortis viroid (CEVd) was detected by observing tissues displaying both severe and mild symptoms from a single Gynura aurantiaca. The variants CEVd-S (severe) and CEVd-M (mild), differing by only five nucleotides confined to the pathogenic (P) domain, remained stable when propagated by rooted cuttings or from successive plants inoculated with tissue extracts or transcripts from cDNA clones. CEVd-S induces a very severe reaction in Gynura that is consistent throughout a range of environmental conditions. However, symptoms resulting from CEVd-M infection can vary from a nonsymptomatic condition to a severe reaction when grown at 40°C. This differential response was confined to a single host, Gynura aurantiaca, and expressed under standard growing conditions. The distinct host responses induced by these variants could not be correlated with any changes in sequence or conformation of the dominant viroid variant, as predicted by molecular modeling. Therefore, the variable symptom expression appears to be associated with a specific temperature-sensitive response of Gynura aurantiaca.

Maintaining Vegetative Potted Purple Velvet Plants

The purple velvet plant (Gynura aurantiaca) has commercial potential as a potted plant due to its attractive purple foliage, if the malodorous flowers can be avoided. Plants were treated with seven concentrations of ethephon, three photoperiodic durations, three light intensities, and combinations of photoperiod and light intensity to inhibit flowering. Although foliar application of ethephon at 1200 to 4800 ppm (μL·L-1) completely inhibited flowering of purple velvet plants, plants were stunted and cutting harvest was impossible. Flowering was promoted at lower application rates of 150 to 300 ppm (μL·L-1). An 8-hour photoperiod increased plant quality and plants had the largest vegetative shoot number and the brightest purple color, compared to 12 or 16-hour photoperiods. All of the shoots were reproductive under the 16-hour photoperiod. Increasing the shade level from 0 to 60% (790 μmol·m-2·s-1 to 230 μmol·m-2·s-1) increased the number of vegetative shoots at 74 and 108 days after treatment commenced but reduced the total number of shoots by 28% at day 108. Plants grown under60% shade and short days had 94% vegetative shoots 102 days after placement in treatment. Growing plants under 8-hour photoperiod and 60% shade from fall to spring is recommended to maintain vegetative stock plants and produce high quality marketable plants. Chemical names used: (2-chloroethyl) phosphonic acid (ethephon).

154 Suppressing Purple Passion (Gynura aurantiaca) Flowering Using Selected Plant Growth Regulators

Gynura aurantiaca is a colorful foliage plant with creeping stems and velvety purple hairs that cover the green leaves. It grows rapidly, but is cultivated primarily for those attractive purple leaves. Annually during the spring, this plant produces prominent flowers both in appearance and smell, gaudy and malodorous. Flowering coupled with acquiring an over-grown leggy appearance have been key limitations in its production and use in interiorscaping. This study was undertaken to determine if an available commercial plant growth regulator could inhibit flowering. A-Rest (ancymidol), B-Nine (daminozide), Bonzi (paclobutrazol), cycocel (chlormequat chloride) and florel (ethephon) each diluted to three different concentrations were sprayed in two applications in early spring at 2-week intervals. Flowering and bud numbers and plant growth (number of lateral shoots, vine lengths and internode lengths) were recorded. Results indicated that applications of A-Rest, B-Nine, Bonzi and Cycocel, regardless of treatment concentrations, were ineffective in suppressing the flowering of this plant; whereas, florel completely suppressed flowering at the three concentrations used. The florel-treated plants also grew more lateral shoots, which produced a compact and dense bush-look, indicating that appropriate concentrations of florel application not only will stop flowering of purple passion but can also improve and prolong its aesthetic value as a potted or hanging-basket interior plant.

Direct Nucleotide Sequencing of Citrus Exocortis Viroid (CEV)

Citrus exocortis viroid (CEV), the causal agent of bark shelling disease in Poncirus trifoliata (L.) Raf, can be distinguished by its biological properties in Etrog citron and Gynura aurantiaca D. C. CEV isolate obtained from citrus trees of Çukurova region was reverse transcription-polymerase chain reaction assay (RT-PCR). The amplified products were gel purified, and subsequently sequenced without cloning, using the Promega fmol sequencing system. Both CEVc (citron) and CEVg (Gynura) were determined 371 nucleotides (nts) in length. Comparing the nucleotide sequence of CEV isolate from Çukurova region and California isolates of CEV, a number of exchanges were found in the pathogenic and variable domains.

A stable 463 nucleotide variant of citrus exocortis viroid produced by terminal repeats.

An unusual variant of citrus exocortis viroid (CEV) was detected when an inoculum source from Gynura aurantiaca D.C. was used to infect a hybrid tomato (Lycopersicon esculentum Mill. x L. peruvianum). The 92 nucleotide larger variant, CEV D-92, which displayed the characteristic circular and linear viroid structural forms, contained two repeated sequences spanning the V and T2 domains. A dramatic moderation of symptom expression in Gynura accompanied the incorporation of these repeated sequences. A comparison of the sequence and structure of CEV D-92 with coconut cadang-cadang viroid revealed similarities in the regions generating the naturally occurring terminal repeats suggesting a possible preferred site for RNA recombination between viroids.

Isolates of citrus exocortis viroid recovered by host and tissue selection

Isolates of citrus exocortis viroid (CEV) from a single sweet orange citrus source have been selected by sequential passage through the alternative hosts citron, Gynura aurantiaca, a hybrid tomato Lycopersicon esculentum x L. peruvianum, and from disorganized callus culture of the hybrid tomato. The distinctions in symptom expression, titre and electrophoretic mobility among the CEV isolates, operationally termed CEVc (citron), CEVg (Gynura), CEVt (tomato) and CEVcls (callus) are supported by characteristically different nucleotide sequences. The nucleotide sequence of full-length cDNA clones of CEVc purified from citron shows exchanges not reported for any previously described CEV variant. An unusual number of exchanges have been localized in the terminal domains of all the isolates analysed here. A common pattern of nucleotide exchanges, described as a 'tomato signature', can be detected in all of the isolates derived from hybrid tomato tissues.

The persistence of engineered Agrobacterium tumefaciens in agroinfected plants.

Several plant species, including tomato (Lycopersicon esculentum), Gynura aurantiaca, avocado (Persea americana), and grapefruit (Citrus paradisi) grafted on Troyer citrange (Poncirus trifoliata x C. sinensis) were "agro-infected" with Agrobacterium tumefaciens strain LBA-4404, carrying a mini-Ti plasmid with a dimeric cDNA of citrus exocortis viroid (CEVd). Extracts prepared from tissues of the agroinfected plants 38-90 days after inoculation were plated on selective media and found to contain large amounts of the engineered bacteria. These observations suggest the need for more stringent quarantine measures when handling A. tumefaciens cells harboring constructs for "agroinoculation" with plant viruses or viroids.

Incidence in Cyprus of citrus exocortis viroid and its mechanical transmission

A survey for citrus exocortis viroid (CEV) was conducted in commercial groves of the main citrus‐producing areas of Cyprus during 1987–1990. Of 573 trees sampled, representing 25 species and varieties, 506 (88.3%) were found to be infected when indexed by grafting to seedlings of‘Etrog’ citron (Citrus medica), selection Arizona 861. Levels of infection by CEV were lower in newer introductions than in introductions made before the 1940s. In greenhouse tests, CEV was readily transmitted from citron to healthy citron and gynura (Gynura aurantiaca) by knife‐blade inoculation. Retransmission of CEV from infected gynura back to citron was successful.

Polyamines in Plants Infected by Citrus Exocortis Viroid or Treated with Silver Ions and Ethephon

The levels of polyamines in leaves of Gynura aurantiaca DC and tomato, Lycopersicon esculentum Mill. cv Rutgers, infected with citrus exocortis viroid (CEVd) or treated with silver nitrate or ethephon (2-chloroethylphosphonic acid) were measured by HPLC in relation to development of symptoms. Previously it had been demonstrated that treatment of G. aurantiaca plants with silver nitrate or ethephon closely mimicked the effects of viroid infection in the plants. In the studies reported here, a marked decrease in putrescine level was observed in plants infected by CEVd or treated with silver ions or ethephon. There was no significant change in either spermidine or spermine levels. Treatment of G. aurantiaca plants with specific inhibitors of ethylene biosynthesis (aminoethoxyvinylglycine, Co(2+)) or ethylene action (norbornadiene) prevented the decrease of putrescine associated with silver nitrate treatment and had no effect on spermidine or spermine levels. The development of viroid-like symptoms, the production of associated pathogenesis-related proteins, and the rise in protease activity induced by silver nitrate, were all suppressed by exogenous application of putrescine. The decreased level of putrescine as an ethylene-mediated step in the transduction of the viroid and silver or ethephon signaling is discussed.

Variations in the “cross protection” effect between two strains of citrus exocortis viroid

SUMMARYIn a survey conducted to evaluate the biological properties of several field sources that induced a severe exocortis reaction on citron (Citrus medica L.), a viroid isolate which induced mild symptoms on Gynura aurantiaca was detected. This isolate was characterised as a strain of the citrus exocortis viroid (CEV) by size and homology, and was designated as CEV‐129. Cross protection assays using CEV‐129 as a “protecting” strain against the severe type strain of CEV demonstrated that a mild strain of CEV could provide apparent ‘protection’ against challenge inoculations with the severe strain. The protection effect, however, displayed a variability which ranged from only a brief delay to almost total impairment of symptom expression. The level of protection was dependent upon the length of the interval between the inoculations with the mild and the severe strains. In all cases the effect was temporary since the symptoms and viroid concentration which ultimately prevailed reflected the predominance of the severe strain in the mixed infection. The interpretation of these results and their relationship with previous reports of ‘cross protection’ reactions are discussed along with the consideration of the efficacy and limitations of this term with viroid infection.

Impairment of viroid infection inGynura aurantiacaplants by treatment with 2-chIoroethylphosphonic acid (ethephon)

Ethephon (2-chloroethylphosphonic acid), an ethylene-releasing compound, applied by spraying (3 mM) on apical leaves or pricking (0.2 M) fully expanded leaves of Gynura aurantiaca plants delayed symptom expression in plants inoculated with citrus exocortis viroid (CEV). Only the ethephon-pricked leaves accumulated the pathogenesis-related proteins PI and P2 originally found associated with citrus exocortis viroid (CEV) infection in this plant. No pathogenesis-related proteins appeared in the protected apical leaves until after the protection was overcome. Pathogenesis-related proteins have been implicated in resistance to pathogens. However, this ethephon-induced protection in G. aurantiaca plants was not correlated with detectable increases in the level of PI and P2 or any other protein in the protected leaves.

Synthesis of RNAs Specific to Citrus Exocortis Viroid by a Fraction Rich in Nuclei from Infected Gynura aurantiaca: Examination of the Nature of the Products and Solubilization of the Polymerase-Template Complex

SUMMARY Viroid-specific polymerase activity was detected in preparations rich in nuclei from Gynura aurantiaca infected with citrus exocortis viroid (CEV). The polymerase catalysed the synthesis of several RNAs, shown to be viroid-specific since they could not be observed in control experiments with healthy plants, and they contained CEV-specific sequences most of which were of the same polarity as the viroid RNA. The synthesis of the CEV-specific RNA species was greatly reduced in the presence of 1 μm-α-amanitin, suggesting the involvement of RNA polymerase II in this process. The structure of the viroid-specific RNA species was studied by chromatography on non-ionic cellulose, digestion with RNase under low and high ionic strength conditions, and analysis by polyacrylamide gel electrophoresis in non-denaturing and denaturing systems. The results showed that these RNAs synthesized in vitro contain unit and longer than unit length linear viroid strands forming multistranded complexes with single- and double-stranded regions. The RNAs therefore have the same structural properties as deduced for RNAs isolated from viroid-infected tissues which are the presumed replicative intermediates of the rolling circle mechanism proposed for viroid synthesis. A soluble fraction containing the polymerase-template complex responsible for the synthesis of the CEV-specific RNAs was isolated by treatment of the nuclei-rich preparation with heparin and DNase. This soluble fraction could be of interest in further studies to characterize the components of the polymerase-template complex involved in CEV replication.

Properties of a Viroid-replicating Complex Solubilized from Nuclei

SUMMARY An organelle-free fraction with the ability to synthesize citrus exocortis viroid (CEV) RNA was prepared from nuclei-rich samples taken from CEV-infected Gynura aurantiaca D.C. leaf tissue. This extraction was accomplished in the presence of the detergent sarkosyl. Characterization of the viroid synthetic reaction demonstrated that the solubilized complex retained the properties displayed by intact nuclei. These include optima of 1 mm-MnCl2, 10 mm-MgCl2 and 25 mm-(NH4)2SO4, as well as inhibition by α-amanitin (90% at 4 μg/ml) and by the chelators o-phenanthroline (78% at 5 mm) and hydroxyquinoline (45% at 5 mm). Nucleic acid-binding agents such as ethidium bromide and actinomycin D showed a low, non-specific inhibition at relatively high concentrations. Sucrose gradient sedimentation analysis of the sarkosyl supernatant (SSN) components before and after the RNA synthesis showed that the bulk of the progeny remained associated with the viroid complex which sedimented faster than phenol-treated viroid RNA. A high percentage of the CEV RNA molecules migrated in electrophoresis as the circular form. This suggests that all elements necessary for the synthesis of viroid RNA and processing to circular structures are present in the SSN. This endorses the potential of these subnuclear preparations for the study of the processes involved in viroid replication.