Recent Progresses in Eco-Friendly Fabrication and Applications of Sustainable Aerogels from Various Waste Materials

Tons of waste from residential, commercial and manufacturing activities are generated due to the growing population, urbanization and economic development, prompting the need for sustainable measures. Numerous ways of converting waste to aerogels, a novel class of ultra-light and ultra-porous materials, have been researched to tackle the issues of waste. This review provides an overview of the status of aerogels made from agricultural waste, municipal solid, and industrial waste focusing on the fabrication, properties, and applications of such aerogels. The review first introduced common methods to synthesize the aerogels from waste, including dispersion and drying techniques. Following that, numerous works related to aerogels from waste are summarized and compared, mainly focusing on the sustainability aspect of the processes involved and their contributions for environmental applications such as thermal insulation and oil absorption. Next, advantages, and disadvantages of the current approaches are analyzed. Finally, some prospective waste aerogels and its applications are proposed.

Identification of Pistacia-associated flexivirus 1, a putative mycovirus of the family Gammaflexiviridae, in the mastic tree (Pistacia lentiscus) transcriptome

In this study, we identified the genome sequence of the novel virus Pistacia-associated flexivirus 1 (PAFV1), a putative member of the mycovirus family Gammaflexiviridae (the order Tymovirales), via analysis of a transcriptome dataset for the mastic tree (Pistacia lentiscus, the family Anacardiaceae). PAFV1 was predicted to have three open reading frames (ORFs): ORF1, encoding a replicase (REP) with RNA-dependent RNA polymerase activity; ORF2, a movement protein (MP); and ORF3, a hypothetical protein. The PAFV1 REP sequence showed high similarity to those of three known members of the family Gammaflexiviridae i.e., Entoleuca gammaflexivirus 1 (EnFV1), Entoleuca gammaflexivirus 2 (EnFV2), and Botrytis virus F (BVF). A genome contig of the fungus Monosporascus cannonballus also contained a sequence of an endogenous virus similar to that of PAFV1. Sequence comparison and phylogenetic analysis indicated that PAFV1, EnFV1, and the endogenous virus of M. cannonballus formed a distinct subgroup (apart from EnFV2 and BVF), and may be the founding members of a novel genus in the family Gammaflexiviridae. Notably, MP sequences of PAFV1/EnFV1 showed similarity to the MP sequences of the mycovirus group called tobamo-like mycoviruses (an unassigned taxon), implying that genomic recombination occurred between members of the family Gammaflexiviridae and tobamo-like mycoviruses. Since PAFV1 is phylogenetically related to mycoviruses, PAFV1 may also be a mycovirus that infected a fungus associated with the mastic tree sample, which is evidenced by the presence of fungal ribosomal RNA sequences in the mastic tree transcriptome. Thus, the PAFV1 genome sequence may be useful in elucidating the genome evolution of Gammaflexiviridae and tobamo-like mycoviruses. Keywords: Pistacia-associated flexivirus 1; Gammaflexiviridae; mycovirus, mastic tree.

Identification of a novel plant amalgavirus (Amalgavirus, Amalgaviridae) genome sequence in Cistus incanus

Amalgaviridae is a family of double-stranded, monosegmented RNA viruses that are associated with plants, fungi, microsporidians, and animals. A sequence contig derived from the transcriptome of a eudicot, Cistus incanus (the family Cistaceae; commonly known as hoary rockrose), was identified as the genome sequence of a novel plant RNA virus and named Cistus incanus RNA virus 1 (CiRV1). Sequence comparison and phylogenetic analysis indicated that CiRV1 is a novel species of the genus Amalgavirus in the family Amalgaviridae. The CiRV1 genome contig has two overlapping open reading frames (ORFs). ORF1 encodes a putative replication factory matrix-like protein, while ORF2 encodes a RNA-dependent RNA polymerase (RdRp) domain. An ORF1+2 fusion protein, which functions in viral RNA replication, is produced by a +1 programmed ribosomal frameshifting (PRF) mechanism. A +1 PRF motif UUU_CGU, which matches the conserved amalgavirus +1 PRF consensus sequence UUU_CGN, was found at the boundary of CiRV1 ORF1 and ORF2. Comparison of 25 amalgavirus ORF1+2 fusion proteins revealed that only three different positions within a 13-amino acid segment were recurrently used at the boundary, possibly being selected so as not to interfere with correct folding and function of the fusion protein. CiRV1 is the first virus found to be associated with the Cistus species and may be useful for studying amalgaviruses.

Novel Divavirus (the family Betaflexiviridae) and Mitovirus (the family Narnaviridae) species identified in basil (Ocimum basilicum)

Transcriptome data obtained from a plant sample often contain a large number of reads that are derived from associated RNA virus genomes that were co-isolated during RNA preparation. These virus-derived reads can be assembled into a novel plant RNA genome sequence. Here, a basil (Ocimum basilicum) transcriptome dataset was analyzed to identify two new RNA viruses, which were named Ocimum basilicum RNA virus 1 (ObRV1) and Ocimum basilicum RNA virus 2 (ObRV2). A phylogenetic analysis of the ObRV1 RNA-dependent RNA polymerase (RdRp) motif indicated that ObRV1 is a novel species of the genus Divavirus of the family Betaflexiviridae. ObRV1 is the fourth divavirus species to be identified. The ObRV2 RdRp motif showed sequence similarity to viruses of the genus Mitovirus of the family Narnaviridae, which infect fungal mitochondria. Although most of the known mitoviruses do not produce a functional RdRp using the plant mitochondrial genetic code, the ObRV2 encodes a full-length RdRp using both the fungal and plant mitochondrial genetic codes.

Induction of in vitro flowering in Dendrobium Madame Thong-In (Orchidaceae) seedlings is associated with increase in endogenous N(6)-(Delta (2)-isopentenyl)-adenine (iP) and N (6)-(Delta (2)-isopentenyl)-adenosine (iPA) levels

We analysed the endogenous cytokinin levels of Dendrobium Madame Thong-In seedlings grown in vitro during vegetative and flowering-inductive periods. HPLC was used to fractionate the extracts and radioimmunoassay (RIA) was used for assay of zeatin (Z), dihydrozeatin (DZ), N(6)-(Delta(2)-isopentenyl)-adenine (iP) and their derivatives. Coconut water used in experiments was found to contain high level (>136 pmol ml(-1)) of zeatin riboside (ZR). Protocorms and seedlings cultured in medium with coconut water were found to contain 0.5-3.9 pmol g(-1) FW of the cytokinins analysed. Seedlings (1.0-1.5 cm) cultured in flowering-inductive liquid medium containing 6-benzyladenine (BA, 4.4 muM) and coconut water (CW, 15%) contained up to 200 and 133 pmol g(-1) FW of iP and iPA, respectively. These levels were significantly higher than all other cytokinins analysed in seedlings of the same stage and were about 80- to 150-folds higher than seedlings cultured in non-inductive medium. During the transitional (vegetative to reproductive) stage, the endogenous levels of iP (178 pmol g(-1) FW) and iPA (63 pmol g(-1) FW) were also significantly higher than cytokinins in the zeatine (Z) and dihydrozeatin (DZ) families in the same seedlings. Seedlings that grew on inductive medium but remained vegetative contained lower levels of iPA. The importance of the profiles of iP and its derivatives in induction of in vitro flowering of D. Madame Thong-In is discussed.

High frequency early in vitro flowering of Dendrobium Madame Thong-In (Orchidaceae)

We have successfully developed a method to induce early in vitro flowering of the self-pollinated seedlings of a tropical orchid hybrid, Dendrobium Madame Thong-In. Transition of vegetative shoot apical meristem to inflorescence meristem was observed when young protocorms were cultured in modified KC liquid medium. In contrast, protocorms cultured on Gelrite-solidified medium only produced axillary shoots and roots. CW was required to trigger the transitional shoot apical meristem and BA enhanced inflorescence stalk initiation and flower bud formation. However, normal flower development was deformed in liquid medium but developed fully upon transferring to two-layered (liquid over Gelrite-solidified) medium. Under optimal condition, in vitro flowering was observed about 5 months after seed sowing. Segregation of flower colours was observed in these seedlings and seedpods formed upon artificial pollination of the in vitro flowers.

Investigation of cytokinin-deficient phenotypes in Arabidopsis by ectopic expression of orchid DSCKX1

The plant hormone cytokinin plays a major role in regulating plant growth and development. Here we generated cytokinin-reduction Arabidopsis plants by overexpressing a heterologous cytokinin oxidase gene DSCKX1 from Dendrobium orchid. These transgenic plants exhibited reduced biomass, rapid root growth, decreased ability to form roots in vitro, and reduced response to cytokinin in growing calli and roots. Furthermore, the expression of KNAT1, STM, and CycD3 genes was significantly reduced in the transgenic plants, suggesting that cytokinin may function to control the cell cycles and shoot/root development via regulation of these genes.

Functional characterisation of a cytokinin oxidase gene DSCKX1 in Dendrobium orchid

Cytokinin oxidase plays an important role in the cytokinin regulatory processes. We have cloned a novel putative cytokinin oxidase, DSCKX1 (Dendrobium Sonia cytokinin oxidase), by mRNA differential display from shoot apices of Dendrobium Sonia cultured in the presence of BA. The DSCKX1 gene appears to have three alternative splicing forms and its expression of DSCKX1 was induced in a tissue-specific manner by cytokinins. In transgenic orchid plants overexpressing DSCKX1, the elevated level of cytokinin oxidase activity was accompanied by a reduction of cytokinin content. These plants exhibited slow shoot growth with numerous and long roots in vitro. Their calli also showed decreased capability of shoot formation. Conversly, antisense transgenic plants showed rapid proliferation of shoots and inhibition of root growth combined with a higher endogenous cytokinin content than wild-type plants. Thus DSCKX1 appears to play an important role on cytokinin metabolism and the related developmental programmes in orchid.

Isolation and characterization of the orchid cytokinin oxidase DSCKX1 promoter

The orchid DSCKX1 is a new member of the cytokinin oxidase gene family, which catalyses the degradation of cytokinins bearing unsaturated isoprenoid side chains. A 3.7 kb fragment upstream of the DSCKX1 coding region was isolated, sequenced and characterized by deletion analysis of DSCKX1::beta-glucuronidase gene fusions using transient orchid and stable Arabidopsis transformation systems. Functional analysis of 5' deletions defined the 5'-upstream region that directs the expression in distinct tissues. Regulatory elements affecting the cytokinin induction of the DSCKX1 gene have also been delineated

Spatial and temporal expression of the orchid floral homeotic gene DOMADS1 is mediated by its upstream regulatory regions

The orchid floral homeotic gene, DOMADSI, is a marker gene specifically expressed in the transitional shoot apical meristem during floral transition in Dendrobium Madame Thong-In. DOMADSI is not detectable in vegetative tissues except a weak expression in the stem. Its transcript is uniformly localized in both of the inflorescence meristem and floral primordia, and later expressed in almost all of the floral organs. We isolated and sequenced a 3.5 kb DOMADSI promoter fragment upstream of the transcription start site, demonstrating the location of several putative DNA-binding sites, through which MADS-box and class I knox genes may modulate the DOMADSI expression. To gain insight into the molecular basis of the regulation of DOMADS1, deletion analysis of the DOMADSI::beta-glucuronidase (GUS) gene fusions was performed by means of the stable orchid transformation systems. The study shows that the full-length upstream promoter sequence confers the same spatial and temporal GUS staining pattern as that of the distribution of DOMADSI RNA during orchid development. We also identified the distinct cis-acting regulatory regions required for the control of DOMADS1 expression in vegetative and reproductive tissues, as well as the shoot apical meristem during floral transition.

Lambda exonuclease-based subtractive hybridization approach to isolate differentially expressed genes from leaf cultures of Paulownia kawakamii

Genes that are preferentially expressed in a particular developmental pathway can be isolated by subtractive hybridization (SH). We developed a PCR-based approach coupled with lambda exonuclease digestion that allows for generating single-stranded tester and driver nucleic acids suitable for SH starting from cDNA libraries. An efficient subtraction strategy was developed to overcome some of the problems in the previously described SH protocols, such as the need for large amounts of experimental tissue, RNase contamination during solution hybridization, and postsubtraction recovery of nucleic acids. We used this method to obtain cDNA corresponding to genes expressed during adventitious shoot regeneration from excised leaf cultures of the fast-growing tree Paulownia kawakamii. Over 36 cDNA clones were isolated and 1 of the differentially expressed clones codes for a leucine zipper transcription factor. This clone showed about sixfold higher level of expression in the shoot-forming tissues (tester) compared to that in the callus-forming tissues (driver) of Paulownia, suggesting that differentially expressed genes can be efficiently isolated using this simple lambda exonuclease-based subtractive hybridization method.

The expression of Brostm, a KNOTTED1-like gene, marks the cell type and timing of in vitro shoot induction in Brassica oleracea

We studied the early events of de novo formation of adventitious shoot meristems in stem segments of Brassica oleracea. A regeneration system was used that is efficient, rapid, highly responsive to cytokinins and does not involve callus formation, thus allowing studies on a direct developmental switch of cells in the stem segment to form adventitious shoot meristem cells. Shoot meristem cells and dividing cells were marked from very early stages using in situ hybridization studies with Brostm, a Brassica homologue of the Arabidopsis SHOOTMERISTEMLESS (STM) gene, and a cyclin box-derived probe, Brocyc, respectively. We show that the process of developmental switching starts before any cell division occurs in the stem explants. This switching occurs synchronously both longitudinally and transversely in the explant, in groups of 5-7 phloem parenchyma cells subtending vascular bundles in the explant. Brostm is induced specifically in response to a cytokinin, benzyladenine, within 4 h of treatment and the transcripts persist during cell proliferation leading to shoot differentiation. We also show that during adventitious shoot formation, cells expressing Brostm are distinct from those expressing Brocyc. Lastly, our data suggest that, although developmental switching is initiated synchronously within 4 h of treatment, it requires 8 h of treatment for the establishment of organogenic determinance. The latter process is aynchronous, implying that additional factors formed later than Brostm are required to achieve maximal levels of determined cell populations to form adventitious shoots in vitro.

DOH1, a class 1 knox gene, is required for maintenance of the basic plant architecture and floral transition in orchid

We report here the isolation and identification of an orchid homeobox gene, DOH1, from Dendrobium Madame Thong-In. Analyses of its sequence and genomic organization suggest that DOH1 may be the only class 1 knox gene in the genome. DOH1 mRNA accumulates in meristem-rich tissues, and its expression is greatly downregulated during floral transition. In situ hybridization analysis demonstrates that DOH1 is also expressed in the incipient leaf primordia and is later detected in the same region of the inflorescence apex, as in DOMADS1. Overexpression of DOH1 in orchid plants completely suppresses shoot organization and development. Transgenic orchid plants expressing antisense mRNA for DOH1 show multiple shoot apical meristem (SAM) formations and early flowering. In addition, both the sense and antisense transformants exhibit defects in leaf development. These findings suggest that DOH1 plays a key role in maintaining the basic plant architecture of orchid through control of the formation and development of the SAM and shoot structure. Investigations of DOMADS1 expression in the SAM during floral transition reveal that the precocious flowering phenotype exhibited by DOH1 antisense transformants is coupled with the early onset of DOMADS1 expression. This fact, together with the reciprocal expression of DOH1 and DOMADS1 during floral transition, indicates that downregulation of DOH1 in the SAM is required for floral transition in orchid and that DOH1 is a possible upstream regulator of DOMADS1.

Differential gene expression during floral transition in an orchid hybrid Dendrobium Madame Thong-In

 We have developed an in vitro orchid (Dendrobium grex Madame Thong-In) system as a model for investigating gene expression during floral transition. Total RNA was isolated from vegetative shoot apical meristems (VSAM) and transitional shoot apical meristems (TSAM). Using the mRNA differential display method, we identified 53 cDNA clones differentially expressed in VSAMs and 16 cDNA fragments specifically expressed in TSAMs. Northern blot analysis confirmed that, on the basis of their transcripts, 12 cDNAs decreased and 8 cDNAs increased during floral transition. Sequence analysis suggested that 5 clones are likely to be transcription factors, including one MADS-box gene of the AGL2 subfamily, one class 1 knox gene and one homolog of the Drosophila seven-up gene. Other clones showed homology with those coding for Arabidopsis SOD copper chaperone, CKI and the tobacco 21D7 protein.

Identification and characterization of three orchid MADS-box genes of the AP1/AGL9 subfamily during floral transition

Gene expressions associated with in vitro floral transition in an orchid hybrid (Dendrobium grex Madame Thong-In) were investigated by differential display. One clone, orchid transitional growth related gene 7 (otg7), encoding a new MADS-box gene, was identified to be specifically expressed in the transitional shoot apical meristem (TSAM). Using this clone as a probe, three orchid MADS-box genes, DOMADS1, DOMADS2, and DOMADS3, were subsequently isolated from the TSAM cDNA library. Phylogenetic analyses show that DOMADS1 and DOMADS2 are new members of the AGL2 subfamily and SQUA subfamily, respectively. DOMADS3 contains the signature amino acids as with the members in the independent OSMADS1 subfamily separated from the AGL2 subfamily. All three of the DOMADS genes were expressed in the TSAM during floral transition and later in mature flowers. DOMADS1 RNA was uniformly expressed in both of the inflorescence meristem and the floral primordium and later localized in all of the floral organs. DOMADS2 showed a novel expression pattern that has not been previously characterized for any other MADS-box genes. DOMADS2 transcript was expressed early in the 6-week-old vegetative shoot apical meristem in which the obvious morphological change to floral development had yet to occur. It was expressed throughout the process of floral transition and later in the columns of mature flowers. The onset of DOMADS3 transcription was in the early TSAM at the stage before the differentiation of the first flower primordium. Later, DOMADS3 transcript was only detectable in the pedicel tissues. Our results suggest that the DOMADS genes play important roles in the process of floral transition.

Synergism in replication of cymbidium mosaic potexvirus (CymMV) and odontoglossum ringspot tobamovirus (ORSV) RNA in orchid protoplasts

An in vitro orchid protoplast isolation method to study replication kinetics of CymMV and ORSV was developed. This method allows the isolation of viable and raphid-free petal protoplasts from an orchid hybrid, Dendrobium Sonia (Dendrobium Caesar x Dendrobium Tomie Drake). The optimum field strength for both viral RNA to achieve good efficiency of electroporation was 750 V/cm and the optimum viral RNA concentration required was 1 microgram and 4 micrograms per 2 x 10(6) protoplasts for CymMV and ORSV, respectively. Autoradiographs of Northern blots depicting the viral genomic and subgenomic RNA in the extracts, referred to as the "Replication Footprint Profiles" (RFP) of specific CymMV/ORSV virus were prepared at different time intervals. Viral RNA synthesis reached a maximum at 18 h for CymMV and 24 h for ORSV. When CymMV and ORSV viral RNA were electroporated into the protoplasts simultaneously, detection signals of both the positive and negative strand viral RNA increased as compared to the singly infected protoplasts. Thus, synergism in replication of CymMV and ORSV was observed in orchid protoplasts.

An efficient in vitro method for mass propagation of a woody ornamentalIxora coccinea L

Various factors that affect culture establishment, shoot growth, proliferation and rooting ofIxora coccinea L., a woody shrub, were studied. Stem cuttings (decapitated shoot, three nodes) were the most suitable explants for multiple-shoot proliferation, and when cultured on a woody plant medium (WPM) containing 2.5 μM BA produced axillary shoots which branched repeatedly, yielding an average of 27 shoots per explant after 6 weeks in culture. Kinetin, 2-iP, zeatin and thidiazuron all induced multiple-shoot formation, but were less effective than BA. While the presence of IAA in the multiplication medium was detrimental to shoot proliferation, shoot growth was not affected by IAA. The production of large amounts of basal callus and vitrification of shoots were the major problems to be avoided in proliferating shoot cultures. Addition of TIBA to the multiplication medium markedly reduced basal callusing, while sealing the culture vessels with a fluorocarbon polymer (tetrafluoroethyleneperfluoroalkyl vinyl ether) film (Neoflon PFA film) almost completely eliminated vitrification. A reduction in the number of vitrified shoots was also achieved with AVG treatment. Following this protocol of using BA-supplemented WPM and Neoflon film, it would be possible to produce more than 100,000 plants from a single stem cutting in 1 year.

High frequency adventitious shoot regeneration from excised leaves ofPaulownia spp. cultured in vitro

High frequency, direct regeneration of shoots was induced in leaf cultures ofPaulownia tomentosa, P. fortunei x P. tomentosa andP. kawakamii. The optimum culture medium for the leaf explants derived from shoot cultures was Murashige-Skoog (MS) medium supplemented with 10 μM indole-3-acetic acid and 50 μM benzyladenine. Up to 40 shoots were obtained over a 4 month culture period from each leaf explant. Rooting occurred spontaneously in the shoots that were about 1 cm tall when subcultured on phytohormone-free MS medium. The plantlets could be transplanted successfully. Some of the transplantedP. tomentosa plantlets flowered in the greenhouse one year after transplanting. The protocol is suitable not only for rapid multiplication of the various species ofPaulownia, but also for analytical studies associated with adventitious shoot regeneration.

The complete sequence of a Singapore isolate of odontoglossum ringspot virus and comparison with other tobamoviruses

The complete sequence of a Singapore isolate of odontoglossum ringspot virus (ORSV-S1) comprises 6609 nucleotides (nt) and four open reading frames (ORFs 1 to 4). The 126/183-kDa RNA-dependent RNA polymerase (RdRp), 33-kDa movement protein (MP) and 18-kDa coat protein (CP) cistrons are located at nt 63-3401/4901, 4807-5718, and 5721-6197 on the genome, respectively. The 5' UTR contains three copies of an 8-base direct repeat and (CAA)n motifs. Characteristic tRNA-like structure and three consecutive homologous regions were present in the 3' UTR. The genomic RNA and MP of ORSV-S1 are one of the longest among all members of the TOV group. Phylogenetic analysis of all four genes indicates evolutionary divergence, but within each gene there are some degrees of evolutionary convergence. The conserved amino acid sequences in the MP can be used for the classification of tobamoviruses.

Delineation of an immunodominant and human T-cell lymphotropic virus (HTLV)-specific epitope within the HTLV-I transmembrane glycoprotein

Antibody reactivity to the transmembrane region of human T-cell lymphotropic virus type I (HTLV-I) envelope, gp21, is observed in virtually all individuals infected with HTLV-I or HTLV-II. Recombinant proteins encoding selected portions of gp21 are described and used to define two immunogenic regions. The first epitope (designated GD21-I) contains amino acids 361 to 404 of the HTLV-I envelope and reacted with all of 54 sera from HTLV-I- and HTLV-II-infected individuals. The second epitope (designated BA21) expresses amino acids 397 to 430 of the HTLV-I envelope and was recognized by 33 of 54 HTLV antisera. To determine the specificity of GD21-I and BA21, sera from 17 HTLV-negative individuals with nonspecific reactivity to p21E were tested. None of these sera reacted with GD21-I, but 16 of 17 sera reacted with BA21. With virtually complete reactivity to sera from HTLV-infected individuals and no reactivity to sera from p21E-reactive uninfected individuals, GD21-I will be useful in immunoassays for the detection of HTLV infection.

An in vitro method for rapid regeneration of a monopodial orchid hybrid Aranda Deborah using thin section culture

A thin section culture system for rapid regeneration of the monopodial orchid hybrid Aranda Deborah has been developed. Thin sections (0.6-0.7mm thick) obtained by transverse sectioning of a single shoot tip (6-7mm), when cultured in Vacin and Went medium enriched with coconut water (20% v/v), produced an average 13.6 protocorm-like bodies (PLB) after 45 days, compared to 2.7 PLB formed by a single 6-7 mm long shoot tip under same culture condition. Addition of α-naphthaleneacetic acid to Vacin and Went medium enriched with coconut water further increased PLB production by thin sections. PLB developed into plantlets on solid Vacin and Went medium containing 10% (v/v) coconut water and 0.5 g l(-1) activated charcoal. With this procedure, more than 80,000 plantlets could be produced from thin sections obtained from a single shoot tip in a year as compared to nearly 11,000 plantlets produced by the conventional shoot tip method.

Nucleotide sequence of a flower-specific MADS box cDNA clone from orchid

An orchid (Aranda deborah) mature flower cDNA library was screened with an agamous cDNA probe from Arabidopsis. One positive clone for agamous gene was isolated, cloned and sequenced. This cDNA clone (om1) has a full length open reading frame of 750 bp corresponding to 250 amino acid residues. Comparison of om1 MADS box with that of its counterparts in tomato and Arabidopisis reveals significantly high homology (> 95%). Northern analysis indicated this gene is expressed in mature flowers and not in young developing inflorescences or young floral buds. In the mature flowers, it is only expressed in petals and weakly in sepals but not in the column (gynostemium).

Rapid detection of cymbidium mosaic virus by the polymerase chain reaction (PCR)

A direct, simple and sensitive method was developed for the detection of cymbidium mosaic virus (CyMV), based on the polymerase chain reaction (PCR). Two oligonucleotide primers were selected from regions that are homologous to potexviruses and CyMV, and used to hybridize with purified viral RNA and particles. This resulted in the amplification of a 313 bp fragment after 30 cycles of PCR in all samples. A less prominent fragment of 227 bp was also obtained due to mispriming of the second primer. The amplified fragments were easily seen in an agarose gel when stained with ethidium bromide. As little as 1 fg of viral RNA (about 200 target copies) or 10 fg of purified virus (approximately 130 viral particles) were detectable. For CyMV infected orchid leaf tissues, 10 microliters aliquots of 1 mm3 tissue homogenate in 1 ml could be detected routinely. All reverse transcription and amplification reactions were carried out in a single tube and results can be obtained within 5 h.

Role of Ethylene on de Novo Shoot Regeneration from Cotyledonary Explants of Brassica campestris ssp. pekinensis (Lour) Olsson in Vitro

The promotive effect of AgNO(3) and aminoethoxyvinylglycine (AVG) on in vitro shoot regeneration from cotyledons of Brassica campestris ssp. pekinensis in relation to endogenous 1-amino-cyclopropane-1-carboxylic acid (ACC) synthase, ACC, and ethylene production was investigated. AgNO(3) enhanced ACC synthase activity and ACC accumulation, which reached a maximum after 3 to 7 days of culture. ACC accumulation was concomitant with increased emanation of ethylene which peaked after 14 days. In contrast, AVG was inhibitory to endogenous ACC synthase activity and reduced ACC and ethylene production. The promotive effect of AVG on shoot regeneration was reversed by 2-chloroethylphosphonic acid at 50 micromolar or higher concentrations, whereas explants grown on AgNO(3) medium were less affected by 2-chloroethylphosphonic acid. The distinctive effect of AgNO(3) and AVG on endogenous ACC synthase, ACC, and ethylene production and its possible mechanisms are discussed.

Recycling of respiratory CO2 during Crassulacean acid metabolism: alleviation of photoinhibition in Pyrrosia piloselloides

The regulation of Crassulacean acid metabolism (CAM) in the fern Pyrrosia piloselloides (L.) Price was investigated in Singapore on two epiphytic populations acclimated to sun and shade conditions. The shade fronds were less succulent and had a higher chlorophyll content although the chlorophyll a:b ratio was lower and light compensation points and dark-respiration rates were reduced. Dawn-dusk variations in titratable acidity and carbohydrate pools were two to three times greater in fronds acclimated to high photosynthetically active radiation (PAR), although water deficits were also higher than in shade fronds. External and internal CO2 supply to attached fronds of the fern was varied so as to regulate the magnitude of CAM activity. A significant proportion of titratable acidity was derived from the refixation of respiratory CO2 (27% and 35% recycling for sun and shade populations, respectively), as measured directly under CO2-free conditions. Starch was shown to be the storage carbodydrate for CAM in Pyrrosia, with a stoichiometric reduction of "C3-skeleton" units in proportion to malic-acid accumulation. Measurements of photosynthetic O2 evolution under saturating CO2 were used to compare the light responses of sun and shade fronds for each CO2 supply regime, and also following the imposition of a photoinhibitory PAR treatment (1600 μmol·m(-2)·s(-1) for 3 h). Apparent quantum yield declined following the high-PAR treatment for sun- and shade-adapted plants, although for sun fronds CAM activity derived from respiratory CO2 prevented any further reduction in photosynthetic efficiency. Recycling of respiratory CO2 by shade plants could only partly prevent photoinhibitory damage. These observations provide experimental evidence that respiratory CO2 recycling, ubiquitous in CAM plants, may have developed so as to alleviate photoinhibition.

Species preservations in an optimal harvest model with random prices

In this paper, we consider an optimal harvest model in which the objective is to maximize the expected return. The unit price of biomass is assumed constant until a random time when the price increases by a given amount. Furthermore, due to obvious environmental protection requirements, it is assumed that the fishery population is bounded from below for all time so as to reduce the danger of species extinction. Clearly, this problem is an optimal control problem in which a random parameter is involved. However, due to its special structure, it is shown that the problem is convertible into a deterministic optimal control problem and hence is solvable by an existing optimal control software package, MISER. The practical implication of several computed results obtained by this approach is discussed. They are also compared with other related results in the literature.

Studies on lysine:N6-hydroxylation by cell-free systems of Aerobacter aerogenes 62-1

Electron microscopic examination has revealed the vesicular nature of the membrane component, of the cell-free system of Aerobacter aerogenes 62-1, which catalyses lysine: N6-hydroxylation. Regardless of the orientation of the vesicles, N-hydroxylation process is still stimulated by pyruvate. Both pyruvate oxidation and lysine: N6-hydroxylation were inhibited by protonophores and Gramicidin S.

Direct somatic embryogenesis from protoplasts of Citrus mitis Blanco

Protoplasts isolated from embryogenic suspension cultures of Citrus mitis were cultured in a medium without any plant growth substances. Somatic embryos developed directly from protoplasts without an obvious intervening callus phase. As many as 1,800 somatic embryos developed from 4 ml of protoplast suspension (density 2×10(6)/ml) cultured for 35 days. Upon transferring the embryoids to medium with 1 mgl(-1) GA3, they developed into plant-lets. Rooted plantlets were obtained in 3 months after protoplast isolation.

Amino acid pools in CHL V79 cells during induction of thermotolerance: reduction in free intracellular glutamine

The amino acid pools in Chinese hamster lung V79 cells were measured as a function of time during hyperthermic exposure at 40.5 degrees and 45.0 degrees C. Sixteen of the 20 protein amino acids were present in sufficient quantity to measure accurately. The total amino acid pool and all individual amino acids, except glutamine, remained relatively constant for at least 90 min at 40.5 degrees C and for 30 min at 45 degrees C. The glutamine pool decreased rapidly to 20% of its control value within 30 min at 40.5 degrees C with a T1/2 = 15 min. At 45 degrees C, the decrease was 36%. Thermotolerance developed at 40.5 degrees C with a T1/2 = 30 min; thus, glutamine depletion preceeds the development of thermotolerance. The depletion of glutamine is probably due to increased metabolism and oxidation of glutamine through the TCA cycle at hyperthermic temperatures. Glutamine, as is true for other amino acids, was shown to protect proteins from thermal inactivation and V79 cells from hyperthermic killing when added in excess (4-10 mM) to the medium during heat stress. However, the stability of the total amino acid pool during the development of thermotolerance indicates that resistance to heat does not result from the accumulation of amino acids which then protect against thermal damage. The effects of the large decrease in the glutamine pool are unknown, although glutamine depletion may act as a signal for part of the heat shock response.

Analysis of all protein amino acids as their tert.-butyldimethylsilyl derivatives by gas-liquid chromatography

A gas chromatographic method for the separation and quantitation of the 20 protein amino acids is described using N-methyl-N(tert.-butyldimethylsilyl)trifluoroacetamide, with 1% tert.-butyldimethylchlorosilane as catalyst, to prepare the tert.-butyldimethylsilyl amino acid derivatives. Alkylsilylation of amino acids proceeds at 140 degrees C in 20 min. The derivatives formed in the one-step reaction are used directly for gas-liquid chromatographic analysis, using a flame-ionization detector, without prior isolation or purification. Complete separation and quantitation of all protein amino acids are readily achieved using a 15-m DB-5 capillary column. Strict linearity extends from less than 15 to about 100 ng for all amino acids except Arg, which has a linear range from 50 to 300 ng. The limits of detection, however, range from one to several hundred nanograms. The method was used to analyze the free amino acid pool in carnation petals.

Photosynthetic Carbon Assimilation in a Shootless Orchid, Chiloschista usneoides (DON) LDL: A Variant on Crassulacean Acid Metabolism

Photosynthetic carbon assimilation in the roots of a shootless orchid Chiloschista usneoides (DON) LDL involves the synthesis and accumulation of malic acid from CO(2) in darkness. Malic acid is consumed in the light.The roots do not possess stomata or any means of diurnally regulating the diffusive conductance of the pathway between the internal gas phase of the plant and the atmosphere. Regulation of internal CO(2) concentration near to atmospheric levels avoids a large net loss of CO(2) to the atmosphere during malic acid consumption in the light.The water-absorbing function of the velamen conflicts with the photosynthetic function of the roots. Plants with water-saturated velamina do not acquire CO(2) from the atmosphere at night.