A Developmental Pattern of Flowering in Colored <Emphasis Type="Italic">Zantedeschia</Emphasis> spp.: Effects of Bud Position and Gibberellin

The restricted flowering of colored cultivars ofZantedeschia is a consequence of developmental constraints imposed by apical dominance of the primary bud on secondary buds in the tuber, and by the sympodial growth of individual shoots. GA₃ enhances flowering inZantedeschia by increasing the number of flowering shoots per tuber and inflorescences per shoot. The effects of gibberellin on the pattern of flowering and on the developmental fate of differentiated inflorescences along the tuber axis and individual shoot axes were studied in GA₃ and Uniconazole-treated tubers. Inflorescence primordia and fully developed (emerged) floral stems produced during tuber storage and the plant growth period were recorded. Days to flowering, percent of flowering shoots and floral stem length decreased basipetally along the shoot and tuber axes. GA₃ prolonged the flowering period and increased both the number of flowering shoots per tuber and the differentiated inflorescences per shoot. Activated buds were GA₃ responsive regardless of meristem size or age. Uniconazole did not inhibit inflorescence differentiation but inhibited floral stem elongation. The results suggest that GA₃ has a dual action in the flowering process: induction of inflorescence differentiation and promotion of floral stem elongation. The flowering pattern could be a result of a gradient in the distribution of endogenous factors involved in inflorescence differentialtion (possibly GAs) and in floral stem growth. This gradient along the tuber and shoot axes is probably controlled by apical dominance of the primary bud. Online publication: 7 April 2005     

Changes in carbohydrate contents of <Emphasis Type="Italic">Zantedeschia</Emphasis> leaves under gibberellin-stimulated flowering

The effect of gibberellic acid (GA₃) on the carbohydrate accumulation in relation to vegetative growth of Zantedeschia ‘Black Magic’ plants undergoing transition to flowering was investigated. In response to GA treatment the carbohydrate level increased independently of earlier stimulation of shoot emergence. Under vegetative growth stage the content of reducing sugars of leaf blades was 2.5-fold higher than in control plants, and suggests the stimulation of photosynthetic activity. The changes observed during the flowering, in principle noted in petiole tissues, support the GA-effect on assimilate transport to the sink organs. Moreover, the high level of non-structural carbohydrates in petiole tissues, in particular reducing sugars, can be an effect of photosynthetic activity of these organs and/or essential for osmoregulation and high turgor pressure. The results indicate that apart from the influence on the shoot emergence, the GAs may stimulate the photosynthetic activity from the beginning of shoot growth and are thus responsible for the enhancement of callas flower yield.     

GA signaling and <Emphasis Type=Italic>CO/FT</Emphasis> regulatory module mediate salt-induced late flowering in <Emphasis Type=Italic>Arabidopsis thaliana</Emphasis>

Flowering timing is very important for the reproductive success of higher plants. However, effects of salt on plant flowering and the underlying molecular mechanisms are largely unknown. Here, we show that salt stress delays flowering in Arabidopsis in a dose-dependent manner. Mild salt stress (≤50 mM NaCl) promoted and prolonged the vegetative growth, whereas high salinity (≥100 mM NaCl) largely delayed or inhibited the transition from vegetative growth to reproductive development. The gibberellin (GA)-pathway plays an important role in this phenotype, and application of exogenous GA could restore late flowering induced by salt. In addition, the CONSTANS (CO)/FLOWERING LOCUS T (FT) module may also play a critical role in mediating the effects of salt on flowering. The mRNA abundance of CO was significantly reduced by salt stress in a dose-dependent manner. The constans (co-2) mutants did not respond to moderate salt stress, whereas over-expressing CO manifested no delay in flowering time in response to salinity. Expression of FT, SOC1 and LFY in the downstream of the pathways was also reduced by salt according to dose. Moreover, salt-sensitive mutant salt overly sensitive3 (sos3) exhibited greater sensitivity in flowering, further suggesting that ion disequilibrium mediates salt-induced late flowering. Kexue Li and Youning Wang contributed equally to this report.     

Cold storage and cryopreservation of hairy root cultures of medicinal plant <Emphasis Type=Italic>Eruca sativa</Emphasis> Mill., <Emphasis Type=Italic>Astragalus membranaceus</Emphasis> and <Emphasis Type=Italic>Gentiana macrophylla</Emphasis> Pall.

To explore the possibility of an effectively long-term preservation of the germplasm of the HR lines of medicinal plant Astragalus membranaceus, Gentiana macrophylla Pall., and Eruca sativa Mill., both cold storage and cryopreservation approaches were attempted and compared. After 5-month cold storage on half strength Murashige and Skoog (1962) (1/2 MS) agar medium (AM), up to 82.9, 75.7, and 100% of the A. membranaceus, G. macrophylla and E. sativa hairy roots (HRs) recovered growth, respectively. The survival rates of A. membranaceus and G. macrophylla HRs significantly decreased, whereas that of E. sativa HR was unchanged with the addition of increased levels of exogenous abscisic acid (ABA) during cold storage. Using the encapsulation–vitrification (EV) method for cryopreservation, the G. macrophylla HRs died, whereas up to 6 and 73% of the A. membranaceus and E. sativa HRs survived, respectively. The HR lines evaluated with both methods showed no significant differences in morphology and growth rate compared with controls that were not subjected to preservation methods. These results suggest that cold storage is a more suitable alternative for the HR lines of the three studied plant species and that specificity of plant species have profound effects on the effectiveness of preservation.     

Thidiazuron Promotes <Emphasis Type=Italic>In Vitro</Emphasis> Plant Regeneration of <Emphasis Type=Italic>Arachis correntina</Emphasis> (<Emphasis Type=Italic>Leguminosae</Emphasis>) via Organogenesis

Arachis correntina (Burkart) Krapov. & W.C. Gregory is a herbaceous perennial leguminous plant growing in the Northeast of the Province Corrientes, Argentina. It is important as forage. The development of new A. correntina cultivars with improved traits could be facilitated through the application of biotechnological strategies. The purpose of this study was to investigate the plant regeneration potential of mature leaves of A. correntina in tissue culture. Buds were induced from both petiole and laminae on 0.7% agar-solidified medium containing 3% sucrose, salts and vitamins from Murashige and Skoog (MS) supplemented with 0.5–25 M thidiazuron (TDZ). Shoot induction was achieved by transference of calli with buds to MS supplemented with 5 M TDZ. Fifty-four percent of the regenerated shoot rooted on MS + 5 M naphthaleneacetic acid. Histological studies revealed that shoots regenerated via organogenesis.     

Alanine racemase from the green alga <Emphasis Type=Italic>Chlamydomonas reinhardtii</Emphasis>

Summary. Chlamydomonas reinhardtii, a unicellular green microalga, could grow to a stationary phase having optical density of 2.0–2.5 at 750 nm in Tris-acetate-phosphate (TAP) medium containing 0.1% D-alanine. D-alanine has no inhibitory effect on growth and induced alanine racemase activity 130-fold more than without D-alanine in the green alga. Although C. reinhardtii cultured in the TAP medium showed alanine racemase activity, the content of free D-alanine was only 0.14%. The enzyme was partially purified by ammonium sulfate fractionation followed by three kinds of liquid chromatography using DEAE Toyopearl, Phenyl Sepharose, and TSK G3000 SWXL columns. The specific activity for L-alanine of the partially purified alanine racemase was 3.8 μmol/min/mg. The molecular weight of the enzyme was determined to be approximately 72,000 by gel filtration. The enzyme showed a maximum activity at 45 °C and pH 8.4 and requires pyridoxal 5′-phosphate as a coenzyme.     

Purification of branched-chain amino acid aminotransferase from <Emphasis Type=Italic>Helicobacter pylori</Emphasis> NCTC 11637

Summary. Branched-chain amino acid aminotransferase was purified by several column chromatographies from Helicobacter pylori NCTC 11637, and the N-terminal amino acid sequence was analyzed. The enzyme gene was sequenced based on a putative branched-chain amino acid aminotransferase gene, ilvE of H. pylori 26695, and the whole amino acid sequence was deduced from the nucleotide sequence. The enzyme existed in a homodimer with a calculated subunit molecular weight (MW) of 37,539 and an isoelectric point (pI) of 6.47. The enzyme showed high affinity to 2-oxoglutarate (K _m = 0.085 mM) and L-isoleucine (K _m = 0.34 mM), and V _max was 27.3 μmol/min/mg. The best substrate was found to be L-isoleucine followed by L-leucine and L-valine. No activity was shown toward the D-enantiomers of these amino acids. The optimal pH and temperature were pH 8.0 and 37 °C, respectively.     

The expression of analgesic-antitumor peptide (<Emphasis Type=Italic>AGAP</Emphasis>) from Chinese <Emphasis Type=Italic>Buthus</Emphasis><Emphasis Type=Italic>martensii</Emphasis> Karsch in transgenic tobacco and tomato

The present study aimed to obtain analgesic-antitumor peptide (AGAP) gene expression in plants. The analgesic-antitumor peptide (AGAP) gene was from the venom of Buthus martensii Karsch. Previous studies showed that AGAP has both analgesic and antitumor activities, suggesting that AGAP would be useful in clinical situations as an antitumor drug. Given that using a plant as an expression vector has more advantages than prokaryotic expression, we tried to obtain transgenic plants containing AGAP. In the present study, the AGAP gene was cloned into the plasmid pBI121 to obtain the plant expression vector pBI-AGAP. By tri-parental mating and freeze–thaw transformation, pBI-AGAP was transformed into Agrobacterium tumefaciens LBA4404. Tobacco (Nicotiana tabacum) and tomato (Lycopersicom esculentum) were transformed by the method of Agrobacterium-mediated leaf disc transformation. The transformants were then screened to grow and root on media containing kanamycin. Finally, transformations were confirmed by analysis of PCR, RT-PCR and western blotting. The results showed that the AGAP gene was integrated into the genomic DNA of tobacco and tomato and was successfully expressed. Therefore, the present study suggests a potential industrial application of AGAP expressed in plants.     

Transposon display supports transpositional activity of <Emphasis Type=Italic>P</Emphasis> elements in species of the <Emphasis Type=Italic>saltans</Emphasis> group of <Emphasis Type=Italic>Drosophila</Emphasis>

Mobilization of two P element subfamilies (canonical and O-type) from Drosophila sturtevanti and D. saltans was evaluated for copy number and transposition activity using the transposon display (TD) technique. Pairwise distances between strains regarding the insertion polymorphism profile were estimated. Amplification of the P element based on copy number estimates was highly variable among the strains (D. sturtevanti, canonical 20.11, O-type 9.00; D. saltans, canonical 16.4, O-type 12.60 insertions, on average). The larger values obtained by TD compared to our previous data by Southern blotting support the higher sensitivity of TD over Southern analysis for estimating transposable element copy numbers. The higher numbers of the canonical P element and the greater divergence in its distribution within the genome of D. sturtevanti (24.8%) compared to the O-type (16.7%), as well as the greater divergence in the distribution of the canonical P element, between the D. sturtevanti (24.8%) and the D. saltans (18.3%) strains, suggest that the canonical element occupies more sites within the D. sturtevanti genome, most probably due to recent transposition activity. These data corroborate the hypothesis that the O-type is the oldest subfamily of P elements in the saltans group and suggest that the canonical P element is or has been transpositionally active until more recently in D. sturtevanti.     

A new name in <Emphasis Type=Italic>Pavetta</Emphasis> L. (<Emphasis Type=Italic>Rubiaceae</Emphasis>)

Summary  The name Pavetta modesta (Hiern) S. E. Dawson is a later homonym of P. modesta Bremek. Pavetta crystalensis is proposed as a new name.     

Cryopreservation of <Emphasis Type=Italic>Robinia</Emphasis><Emphasis Type=Italic>pseudoacacia</Emphasis>

Cryopreservation of Robinia pseudoacacia explants by vitrification achieved 78% survival following the stepwise preculture of shoot tips in (0.3 + 0.5 + 0.7 M) sucrose with a 80 min incubation in PVS2; compared to 87% survival after desiccation of explants to 30% water content, following 3 days alginate bead (with glycerol and sucrose treatments) preculture in 0.7 M sucrose.     

A new species of <Emphasis Type=Italic>Cortinarius</Emphasis> sect. <Emphasis Type=Italic>Orellani</Emphasis> from Japan

Cortinarius breviradicatus sp. nov., found in deciduous forests, is described and illustrated from Niigata, Japan. It is characterized by its medium-sized to large dark brown basidiocarp, acutely conical pileus, and rooting stipe, and by subglobose to broadly ellipsoid basidiospores. In addition, the extracting solution from its basidiocarps exhibits a strong fluorescence around 400–430 nm in ultraviolet radiation (250 nm), which was observed in a species of Cortinarius sect. Orellani. The new species belongs to the section Orellani. The differences between the new taxon and similar species are briefly discussed.     

Disrupting Abscisic Acid Homeostasis in Western White Pine (<Emphasis Type="Italic">Pinus monticola</Emphasis> Dougl. Ex D. Don) Seeds Induces Dormancy Termination and Changes in Abscisic Acid Catabolites

To investigate the role of abscisic acid (ABA) biosynthesis and catabolism in dormant imbibed seeds of western white pine (Pinus monticola), ABA and selected catabolites were measured during a combined treatment of the ABA biosynthesis inhibitor fluridone, and gibberellic acid (GA). Fluridone in combination with GA effectively disrupted ABA homeostasis and replaced the approximately 90-day moist chilling period normally required to break dormancy in this species. Individually, both fluridone and GA treatments decreased ABA levels in the embryos and megagametophytes of white pine seeds compared to a water control; however, combined fluridone/GA treatment, the only treatment to terminate dormancy effectively, led to the greatest decline in ABA content. Fluridone treatments revealed that a high degree of ABA turnover/transport occurred in western white pine seeds during the initial stages of dormancy maintenance; at this time, ABA levels decreased by approximately two-thirds in both embryo and megagametophyte tissues. Gibberellic acid treatments, both alone and in combination with fluridone, suggested that GA acted transiently to disrupt ABA homeostasis by shifting the ratio between biosynthesis and catabolism to favor ABA catabolism or transport. Increases in phaseic acid (PA) and dihydrophaseic acid (DPA) were observed during fluridone/GA treatments; however, increases in ABA metabolites did not account for the reduction in ABA observed; additional catabolism and/or transport of ABA and selected metabolites in all probability accounts for this discrepancy. Finally, levels of 7′ hydroxy-ABA (7′OH-ABA) were higher in dormant-imbibed seeds, suggesting that metabolism through this pathway is increased in seeds that maintain higher levels of ABA, perhaps as a means to further regulate ABA homeostasis.