Showing papers in "Journal of Plant Biology in 1999"

Binary Vectors for Efficient Transformation of Rice

Abstract: We constructed binary vectors that were designed for transfer and expression of a gene into rice chromosomes. The binary vectors contained the hygromycin-resistance gene for selection of transformants and multiple-cloning sites within the transfer DNA. In addition, vectors were designed to express foreign genes using four kinds of promoters. We also report a procedure for efficient transformation of rice plants using scutellum-derived calli and theAgrobacterium strain LBA4404.

Germin-like proteins: structure, phylogeny, and function

Abstract: Germin-like proteins (GLPs) are a large family of polypeptides present in all plants that share high identity to wheat germin. Germin is a 130 kDa homooligomeric glycoprotein composed of 26 kDa subunits, which was originally identified in monocots (McCubbin et al., 1987). It is expressed in developing seedlings, although it is not found in mature seed, nor in immature embryos. Rather, its synthesis is induced within five hours following imbibition of seeds. Its expression increases as the embryo grows (Thompson and Lane, 1980; Grzelczak and Lane, 1984) and accumulates in the apoplast (Lane et al., 1986). Germin was originally described as a relatively rare protein that was present only in germinating wheat; however, with the advent of genome sequencing projects, it has become increasingly evident that germin and the related GLPs are indeed ubiquitous in the plant kingdom. The best characterized family of germin-like proteins is found in Arabidopsis (Table 1), where there are at least 27 individual family members (Membr~ et al., 1997; Carter et al., 1998; Sage-Ono et al., 1998). A similar large family is known to occur in rice, in which at least eight GLP cDNAs have been deposited in the databases and hexaploid wheat which contains at least seventeen members (Lane et al., 1991). Within the past five years, numerous reports indicate that expression of GLPs occurs in all major plant tissues as well as some unusual sources including pollen (Leitner et al., 1998) and a GLP that is secreted into floral nectar. GLPs are also highly expressed. Of the 35,680 cDNAs that have been deposited in the Arabidopsis thaliana EST databases, surprisingly 39 of these encode germin-like proteins. Thus, mRNAs encoding GLPs represent about 0.1% of all of the mRNAs cloned in this project. Further, among ESTs from Mesembryanthemum crystallinum plants, germin-like proteins are one of the most abundant families of proteins representing 1.9% of all mRNAs examined (JC Cushman & CB Michalowski, personal communication). Thus, these highly abundant, extracellular

Regulation of Both Light- and Auxin - Mediated Development by the Arabidopsis lAA3 / SHY2 Gene

Abstract: Light affects plant growth and development throughout the life cycle. However, light signals do not function autonomously but should be integrated with endogenous developmental factors such as the plant hormone auxin to specify correct developmental decisions. We have previously reported that theArabidopsis shy2-1D mutation alters various light responses, including highly photomorphogenic development in darkness. Here we show that the mutation also alters various auxin responses, including constitutive formation of lateral roots and reduced auxin sensitivity in inhibition of hypocotyl and root growth. The mutation is a gain of function mutation occuring in theIAA3 gene, one of theAux/IAA family genes encoding putative transcription factors of auxin-responsive genes. These results suggest that IAA3/SHY2 may play important roles in both light-and auxin-mediated development Considering that Aux/IAA proteins and auxin response transcription factors interact with one another, we propose that IAA3/SHY2 may integrate light signals into auxin-mediated developmental responses.

An Adaptive Feature of Some Mangroves of Sundarbans , West Bengal

Abstract: Mangrove taxa, apart from their morphological characters, have some unique leaf anatomical features which are very much related to their adaptation as the plants grow in unstable, variable and saline environments with regular tidal influence. Special stomatal structures with extended cuticles render the transpiration rate in many taxa. The presence of glandular and non-glandular hairs on the abaxial and/or adaxial leaf surfaces in some taxa are related to salt secretion of these plants. Comparatively large amounts of water storage tissues occur in the hypodermal or mesophyll tissue of the leaves, reflecting the adaptive nature of mangroves in their stressful habitat. The occurrence of terminal tracheids helps with capillary water storage within the leaf. The coriaceous nature of the leaves in some taxa is due to the presence of sclereids within the mesophyll region. It is noted thatHeritiera is unsuitable to the highly saline habitat of the Sundarbans forest region because of some anatomical peculiarities.

Systematic significance of seed coat morphology inSilene L. s. str. (sileneae-caryophyllaceae) from Korea

Abstract: Seeds of eight species ofSilene s. str. in Korea were examined with a dissecting stereomicroscope and a scanning electron microscope (SEM) to evaluate the systematic significance of seed coat microstructure. The seeds ofSilene s. str. were characterized by triangular or reniform shape, planed or concave dorsal surface in outline, tuberculate or colliculate testa, and sinuated cell margin. Based on the degree of grooves and invagination at dorsal surface, the seeds of the examined taxa ofSilene s. str. fall into two distinct groups: (I) dorsal grooves inconspicuous, surface planed (Silene jenisseensis andS. repens), (II) dorsal grooves conspicuous, surface concave (six remaining taxa). Within each group, seeds of all species may be further distinguished based on shape, size, and testa surface sculpturing. A key to the different species or groups of species is provided, and the systematic significance between/among the taxa is also briefly discussed.

Changes in the isozyme composition of antioxidant enzymes in response to aminotriazole in leaves of Arabidopsis thaliana

Abstract: The changes in isozyme profiles of catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX), and glutathione reductase (GR) during severe deactivation of total CAT activity by aminotriazole (AT) treatment were investigated in the leaves ofArabidopsis thaliana (Columbia ecotype) in relation to H2O2-mediated oxidative stress. In spite of striking deactivation of total CAT activity by 0.1 mM AT, there were no significant differences in H2O2 levels or total leaf soluble protein contents including a Rubisco in both the control and AT-treated leaves. On the other hand, one specific protein band (molecular mass, 66 kD) was observed on the SDS-gel from leaf soluble proteins whose staining intensity was strikingly enhanced by AT treatment for 6 h. However, this band disappeared at 12 h. In the native-gel assays of CAT, POD, APX and GR isozymes, AT remarkably inhibited the expression of the CAT1 isozyme with no effects on CAT2 and CAT3, and generally had no effect on POD isozyme profiles. However, AT stimulated the intensity of activities of pre-existing APX1 and GR1 isozymes. In particular, it induced a new synthesis of one GR isozyme. Therefore, these results collectively suggest that a striking deactivation of total CAT activity by AT inA. thaliana leaves largely results from the suppression of CAT1 isozyme, and that APX1, GR1, and a newly synthesized GR isozyme could complement the role of CAT1 to metabolize H2O2 into non-toxic water.

Molecular cloning and characterization of constans-like cdna clones of the fuji apple

Abstract: Two cDNA clones,MdCOL1 andMdCOL2, encoding CONSTANS (CO)-like proteins were isolated from an apple (Malus domestica cv. Fuji) fruit cDNA library. Both proteins contain two zinc finger motifs at the amino terminal end and a putative nuclear localization domain at the carboxyl terminal end. Genomic DNA blot analysis suggests that theCO-like genes are members of a small multigene family. RNA blot and RT-PCR analyses revealed that these genes are expressed in every organ that was examined. However, the expression levels were higher in floral buds and fruits at their early developmental stages compared to late reproductive stages or vegetative organs. Such expression patterns are quite different from those of theCO-like genes fromArabidopsis, which show strong organ specificity in either roots, cauline leaves, or flowers. These results indicate that the appleCO-like genes are significantly different from theArabidopsis genes and that they appear to play important roles in reproductive organ development.

Plant distribution in relation to soil properties of reclaimed lands on the West Coast of Korea

Abstract: Plant species distribution was studied on five reclaimed lands and one intertidal flat (control) on the western coast of Korea. Nineteen soil properties were analyzed. Of these, soil moisture, electrical conductivity, and levels of Na and Cl had the greatest effect on plant distribution. The plant species were divided into four groups, according to the amount of soil moisture found at their habitats.Triglochin maritimum andTypha angustata were found on the wettest sites;Phragmites communis, Carex scabrifolia, Suaeda japonica, Zoysia sinica, andSalicornia herbacea in places with relatively high moisture;Aster tripolium andPhacelurus latifolius in areas with medium levels of moisture; andAtriplex subcordata, Chenopodium virgatum, andTrifolium repens in the driest areas. The species also were divided into four groups, according to the degree of soil electrical conductivity: Highest,S. herbacea, Limonium tetragonum, Suaeda asparagoides, andS. japonica; Relatively high,A. tripolium, C. scabrifolia, P. communis, Artemisia scoparia, andZ sinka; Relatively low,Setaria viridis, C. virgatum, Sonchus brachyotus, A. subcordata, Calamagrostis epigeios, andT. angustata; and Lowest,Imperata cylindrica var.koenigii, Aeschynomene indica, Lotus corniculatus var.japonicus, andT. repens. On reclaimed land, plant species were found in zones, according to the degree of desalinization (i.e., levels of Na and Cl).

Functional role of CAAT box element of the nopaline synthase (nos) promoter

Abstract: The nopaline synthase (nos) promoter is active in a wide range of plant tissues and regulated by various environmental stimuli. It was previously found that the CAAT box region is important for nos promoter activity. In the present study, the location of the CAAT box element was determined by site specific mutation analysis. Point mutations within the conserved CAAT box element significantly reduced the promoter response in transgenic tobacco plants and calli to wounding, H2O2, methyl jasmonate, and 2,4-D, but not to salicylic acid. However, mutations immediately upstream from the CAAT box did not affect these responses. These results suggest that the CAAT box element is important in responding to certain stimuli.

Foliar responses ofPeristrophe bicalyculata to coal smoke pollution

Abstract: Study of the foliar responses ofPeristrophe bicalyculata (Reth) Nees to the pollution caused by thermal power plant emissions revealed that the stomatal size, pore length, density, and index, as well as the photosynthetic rate and total chlorophyll content were reduced inP. bicalyculata plants at the polluted site in pre-flowering, flowering as well as post-flowering stage of plant growth. Contrary to this, stomatal conductance increased at each stage. The intercellular level of carbon dioxide was raised in the pre-flowering and flowering stages but decreased later at the polluted site.

Plant community structure in reclaimed lands on the West Coast of Korea

Abstract: To clarify the vegetation structure of salty areas, species distribution was survayed according to topography, species association, community ordination, and community classification. We studied one natural tidal flat and five reclaimed lands on the western coast of Korea. Species composition and vegetation profiles changed conspicuously over time and by topographical regions. Regardless of the time that elapsed after reclamation, halophytes and glycophytes coexisted on the sites where the leaching of soil salts was slow. Species association was weak among plants in the early stages on reclaimed lands. With time, however, the strength of species associations increased among halophytes and glycophytes, and the two groups were linked by salt-tolerant glycophytes. This resulted in a series of species associations on old reclaimed lands. In the study of plant community ordination, halophytic communities were located on one side of axis I, glycophytic communities on the other. Several communities of salt-tolerant glycophytes were located between the two groups. When key species were used to classify communities, we found that halophytic and glycophytic communities were intermixed.

Inhibition of auxin-induced ethylene production by salicylic acid in mung bean hypocotyls

Abstract: Salicylic acid (SA), a common plant phenolic compound, influences diverse physiological and biochemical processes in plants. To gain insight into the mode of interaction between auxin, ethylene, and SA, the effect of SA on auxininduced ethylene production in mung bean hypocotyls was investigated. Auxin markedly induced ethylene production, while SA inhibited the auxin-induced ethylene synthesis in a dose-dependent manner. At 1 mM of SA, auxininduced ethylene production decreased more than 60% in hypocotyls. Results showed that the accumulation of ACC was not affected by SA during the entire period of auxin treatment, indicating that the inhibition of auxin-induced ethylene production by SA was not due to the decrease in ACC synthase activity, the rate-limiting step for ethylene biosynthesis. By contrast, SA effectively reduced not only the basal level of ACC oxidase activity but also the wound-and ethylene-induced ACC oxidase activity, the last step of ethylene production, in a dose-dependent manner. Northern and immuno blot analyses indicate that SA does not exert any inhibitory effect on the ACC oxidase gene expression, whereas it effectively inhibits both the in vivo and in vitro ACC oxidase enzyme activity, thereby abolishing auxin-induced ethylene production in mung bean hypocotyl tissue. It appears that SA inhibits ACC oxidase enzyme activity through the reversible interaction with Fe2+, an essential cofactor of this enzyme. These results are consistent with the notion that ethylene production is controlled by an intimate regulatory interaction between auxin and SA in mung bean hypocotyl tissue.

Changes in hydrogen peroxide content and activities of antioxidant enzymes in tomato seedlings exposed to mercury

Abstract: Thirty-day-old seedlings of tomato (Lycopersicon esculentum Mill) were treated with various Hg concentrations (0, 10, and 50 μM) for up to 20 days, and the hypothesis that Hg induces oxidative stress leading to the reduction of biomass and chlorophyll content in leaves was examined The accumulation of Hg in seedlings increased with external Hg concentration and exposure time, and Hg content in roots exposed to 50 μM Hg for 20 days was about 27-fold higher than that in shoots Furthermore, Hg exposure not only reduced biomass and chlorophyll levels in leaves but also caused an overall increase of endogenous H2O2, lipid peroxidation products (malondialdehyde), and antioxidant emzymes activities such as superoxide dismutase, catalase, and peroxidase in leaves and roots Our results suggest that the suppression of growth and the reduction of chlorophyll levels in tomato seedlings exposed to toxic Hg levels may be caused by an enhanced production of active oxygen species and subsequent high lipid peroxidation

Expression patterns of theNPP1 protein phosphatase gene and biochemical activity of its encoded protein

Abstract: TheNPP1 cDNA encoding the catalytic subunit of a type 1 serine/threonine protein phosphatase (PP1) was previously cloned and characterized inNicotiana tabacum (Plant Mol Biol 36, 315–322,1998). In this study, the expression patterns ofNPP1 mRNA in response to various stimuli were examined to gain insight on the cellular function of the NPP1 protein.NPP1 mRNA accumulation was stimulated by Ca++, wounding, fungal elkitiors, and chitosan in leaves. However, with abscisic acid treatment, no change in transcript levels was observed. The recombinant NPP1 protein was catalytically active and could dephosphorylate the autophosphorylated recombinant NtCDPK1, a calcium-dependent protein kinase from tobacco.

Ultrastructure of amyloplasts and intercellular transport of old and new scales inFritillaria ussuriensis

Abstract: Amyloplast structure and intercellular transport in old and new scales ofFritillaria ussuriensis were observed by means of electron microscope. Most amyloplasts in old scales contained one starch grain, which was constructed by the layered deposition of starch around the hilum. Membrane systems and stroma of amyloplasts were pushed aside to form a shell surrounding the starch grain. In contrast, amyloplast shells in new scales contained a relatively light stroma and few internal membranes that were not organized into grana and stroma thylakoids. Active intercellular transport was observed in both new and old scales. Encytosis and exocytosis were common in the cell membrane and produced many vesicles containing numerous particles and filaments. These results lay the foundation for the further study on the mechanisms of growth and development in

Distribution and phytotoxicity of cadmium in tomato seedlings

Abstract: Thirty-day-old seedlings of tomato (Lycopersicon esculentum cv. Kwangsoo) were treated with various cadmium (Cd) concentrations (0, 10, 50, 100, and 500 μM) for up to 20 days, and the detailed distribution of absorbed Cd and its phytotoxicity in different plant parts (root, stem, and leaves) were investigated. The accumulation of Cd in plants increased with external Cd concentrations and Cd was strongly retained by roots, with less than 30% of the absorbed Cd being transported to shoots. Among the leaves, the lower positioned older leaves accumulated more Cd than the younger leaves. Furthermore, Cd-exposure not only reduced the dry weight and length of both shoot and root, chlorophyll levels in leaves, and levels of photosynthesis, but also enhanced the concentration of malondialdehyde (a lipid peroxidation product) in all plant parts. Our results indicate that the physiological impairment of tomato seedlings exposed to toxic levels of Cd may be related to the internal distribution of absorbed Cd, prolonged exposure, and oxidative stress in different plant parts.

Modified plasmodesmata inSorghum (Sorghum bicolor L Moench) leaf tissues infected by maize dwarf mosaic virus

Abstract: The early acute response (EAR), a type of hypersensitive response, is defined by small chlorotic spots at the base of the youngest leaf of sorghum (Sorghum bicolor L. Moench) cultivar HOK, and usually appears within five days after inoculation with maize dwarf mosaic virus strain A (MDMV-A). These chlorotic spots become necrotic one to two days later and the leaf tissues are rapidly killed. In leaf tissues showing EAR, plasmodesmal fields contained many modified plasmodesmata of various sizes and structures within thickened cell walls. The membranous vesicles and tubules, derived from the extended terminal structures of modified plasmodesmata, were blocked by callose-like deposits in the area between the cell wall and plasmalemma. Also observed were two opposite-directed channels united via a central cavity at the middle lamella of the cell wall, one end of which was connected to the plasmalemma, but the other end sealed off to form a bulbous extension. The localized structure, an extraprotoplasmic sac containing aggregates of elongated virus-like particles associated with the modified plasmodesmata, was located between the plasmalemma and the cell wall. The sac was bound by membranes, and appeared to be sealed and completely excluded from the protoplasm. Extraprotoplasmic sacs appeared to be derived from the terminal extension of modified plasmodesmata, and these modification seem to be related to restriction of the viral spread.

Aluminum uptake and aluminum-induced rapid root growth inhibition of rice seedlings

Abstract: Aluminum (Al) inhibits root growth in acidic soil, but the site of action of Al remains unclear. We investigated whether the rate of Al accumulation correlates to Al-indeced rapid root growth inhibition in rice seedlings (Oryza sativa L. cv. Youngnam). Growth of roots was significantly inhibited by 100 μM AICI3, as early as 1 h after the treatment. The inhibition of root growth was strongly dependent on Al concentration (l50 = 20 (μM) and Al-exposure time (l50 = 23 min at 25 μM Al) in a solution of 10 mM KCI and 1 mM CaCl2 buffered by 10 mM Mes/KOH (pH 4.5). Using ICPES, massive uptake of Al by roots was observed even at 15 min treatment of 25 μM Al. The kinetics of Al uptake by the roots closely corresponded to the inhibitory effects of Al on root growth. When the roots of seedlings were exposed to 50 (μM Al for 1 h, then sectioned and stained with hematoxylin, all cell types of the roots showed the presence of Al in the cytoplasm. These results indicate that Al was rapidly taken up into the root cells and thereby reduced root growth.

Structural changes in root and shoot ofBacopa monniera in response to salt stress

Abstract: Various concentrations of salt (NaCI) were shown to have an influence on the differentiation of tissues in the root and stem ofBacopa monniera (L) Wettst. Higher concentrations induced drastic changes in roots grown on salt-supplemented media; epidermal and cortical cells experienced changes in shape, size, and orientation and/or were got disintegrated. A low concentration of salt induced a profuse development of root hairs which gradually disappeared at higher concentrations. Air spaces in the stem cortex were enlarged and xylem cell walls in the vascular ring were thickened.

Construction of small binary vectors forAgrobacterium-Mediated transformation in plants

Abstract: Despite the popular use of theAgrobacterium-mediated method for transforming plants, only a very limited number of binary vectors are available. In addition, those binary vectors are rather inconvenient for plasmid manipulation because of their large size. Here, we report the construction of small binary vectors, pBmin1 and pBminGFP1, forAgrobacterium-mediated transformation. The sizes of pBmin1 and pBminGFP1 are approximately 5.0 kb and 6.5 kb, respectively. These vectors contain one kanamycin resistance gene, with a double promoter for expression in both bacteria and plant cells. Vector pBminGFP1 has the 35S-GFP chimeric gene as a reporter. These small binary vectors would greatly facilitate plasmid manipulation and plant transformation.

NsMADS1, a member of the MADS gene family fromNicotiana sylvestris

Abstract: A cDNA clone,NsMADS1, was isolated fromNicotiana sylvestris. Sequence homology analysis indicated that the gene is a member of the SQUA subfamily. Its transcript was detectable primarily in reproductive organs, especially in sepals and carpels. When the gene was expressed ectopically in tobacco plants, no phenotypic alteration was observed. Thus,NsMADS1 appears to be a new member of the MADS gene family.

The response to oxidative stress induced by magnesium deficiency in kidney bean plants

Abstract: To understand the plant response to oxidative stresses, we studied the influence of magnesium (Mg++) deficiency on the formation of hydrogen peroxide (H2O2), malondialdehyde (MDA), and protease activity in kidney bean plants. The expression pattern of proteins under Mg++ deficiency also was examined via two-dimensional electrophoresis. The formation of H2O2 and MDA increased in the primary leaves of plants grown in a nutrient solution deficient in Mg++. Protease activity in Mg++-deficient plants was also higher than in those grown with sufficient Mg++. The expression pattern of the proteins showed that 25 new proteins were generated and 64 proteins disappeared under Mg++-deficient conditions. Therefore, a deficiency in Mg++ may cause oxidative stress and a change in protein expression. Some of these proteins may be related to the oxidative stress induced by Mg++ deficiency.

Ultrastructure and development of nonarticulated laticifers in seedlings ofEuphorbia maculata L.

Abstract: The ultrastructure of nonarticulated laticifers in the seedlings ofEuphorbia maculata was studied at various developmental stages. The apical regions of the seedling laticifers growing intrusively contained large nuclei with mainly euchromatin and dense cytoplasm possessing various and many organelles such as rich ribosomes, several small vacuoles, giant mitochondria with dense matrices, rough endoplasmic reticulum, dictyosomes, and proplastids. This result suggested that the apical regions of laticifers were metabolically very active. Laticifers in seedlings at the first-leaf developmental stage did not contain latex particle. In seedlings at second-leaf growth stage, the laticifer cells contained numerous and elongated small vacuoles. These vacuoles appeared to arise by dilation of the endoplasmic reticulum and frequently possessed osmiophilic or electron-dense latex particles. The small vacuoles fused with the large vacuole occupying the central portion of the subapical region of laticifers, and then the latex particles were released into the large central vacuole. The latex particles varied in size and were lightly or darkly stained. Proplastids with a dense matrix and a few osmiophilic plastoglobuli were filled with an elongated starch grain and thus were transformed into amyloplasts. Latex particles were initially produced in the laticifers after seedlings had developed their second young leaves. In seedlings at forth-leaf stage, latex particles with an alveolated rim were found in the laticifers.

Molecular evidence for the phylogenetic position of Hanabusaya asiatica Nakai (Campanulaceae), an endemic species in Korea

Abstract: The phylogenetic relationship of the Korean endemic genus,Hanabusaya, to other campanulaceous genera has been controversial since it was described by Nakai in 1911. Three genera of Campanuloideae,Symphyandra, Adenophora, andCampanula, have been considered closely related by various taxonomists on the basis of anther shape, gross morphology, and pollen characters, respectively. We have tested these competing taxonomic hypotheses using the internal transcribed spacer (ITS) sequences of nuclear ribosomal DNA from 12 taxa representing 7 genera of Campanulaceae. The molecular phylogeny indicates strongly thatHanabusaya is more closely allied toAdenophora than toCampanula orSymphyandra. The phylogenetic affinity ofHanabusaya andAdenophora is supported by a 100% bootstrap value and a high decay index (13). The average sequence divergence value (Kimura’s 2-parameter method) betweenHanabusaya and theAdenophora species is 2.58. The value is significantly (about ten times) lower than the ones observed betweenHanabusaya and the species ofCampanula (average of 23.52) and betweenHanabusaya andSymphyandra (24.95). The ITS sequence phylogeny suggests that some morphological characters, such as fused anthers and corolla shape, are homoplastic in the Campanulaceae genera.

Turnover of cell-wall polysaccharides during somatic embryogenesis and development of celery (Apium graveolens L.)

Abstract: Non-embryogenic cells (NEC) and embryogenc cells (EC) were separated from cell clusters derived from the hypocotyl segments of celery seedlings, which had been suspension-cultured in MS medium supplemented with 105 M 2,4-D. The EC formed globular embryos in medium without 2,4-D. The globular embryo developed through heart-shaped, torpedo to cotyledonary embryos within 10 days. The EC and developing embryos were fractionated into symplastic [MeOH, hot water (HW), starch (S)] and apoplastic [pectin, hemicellulose, TFA (trifluoroacetic acid)-soluble and cellulose] fractions. The EC contained lower levels of sugar in the MeOH fraction and higher levels of starch than NEC. In the apoplastic fractions, there were no differences of total sugar amounts between NEC and EC. Cellulose contents were about 10% of the wall polysaccharides. During somatic embryogenesis, total sugar contents of the MeOH and HW fractions increased till the heart-shaped embryo stage, and then decreased during the torpedo and cotyledonary embryo stages. The sugar contents of the starch, pectin, TFA-soluble, and cellulose fractions did not change during the stages mentioned above. However, the hemicellulose substances remarkably increased during embryogenesis, and then decreased as the development proceeded. The neutral sugar components of the hemicellulosic fractions were analyzed. Arabinose increased markedly in EC to the globular embryo stage, but decreased as the development proceeded. Galactose increased only at the torpedo and cotyledonary embryo stages. Xylose was present at lower levels in all stages of embryogenesis than in the differentiated hypocotyl cell walls. These results suggest that there was a high turnover of arabinogalactan polysaccharides during embryogenesis, and that xylan accumulated in the cell walls of differentiated cells

Reexamination of sectional classification in far easternEuphorbia subgenusEsula (Euphorbiaceae) using morphological and phenolic data

Abstract: Reexamining the classification proposed by Hurusawa, the phylogeny of Far EasternEuphorbia subgenusEsula was analyzed using thirteen morphological and seventeen phenolic compound data. These data were analyzed independently and in combination using PAUP under the assumptions of Fitch parsimony. Ten species, comprised of three sections and five subsections within Far EasternEuphorbia subg.Esula and one outgroup from subg.Chamaesyce, were used as terminal taxa. The phylogenetic results did not support the sectional classifications within subg.Esula proposed by Hurusawa. SectionDecussatae was nested in the paraphyletic sectEsula in all of the analyses, and the relationship of sectHelioscopiae was equivocal among data sets. The disagreement of data sets over the placement ofEuphorbia ebracteolata is probably due to a hybrid origin of the species and missing phenolic data forE. pallasii. A sister-group relationship of the Korean endemicE. fauriei with the widespreadE. pekinensis was strongly supported by the morphological and phenolic data.

Characterization of chromosomal DNA and DNA polymorphism in Korean cultivars ofAllium sativum L.

Abstract: The genetic background of the garlic (Allium sativum L.) is not well understood, since it is cultivated exclusively by vegetative propagation. To understand its genetic background, a local cultivar, Danyang, was chosen, and several basic characteristics of its chromosomal DNA were examined. Its G + C content was 40.6%, and the relative proportion of fast reassociated sequences, intermediate reassociated sequences, and slow reassociated sequences were 12%, 40%, and 48%, respectively. The genome size, calculated based on reassociation kinetic experiments, was 1.11 x 1010 bp or 12.16 pg per haploid genome. To compare the genetic variation among four local cultivars, Munkyung, Seosan, Euiseong, and Danyang, random amplified polymorphic DNA (RAPD) analysis was performed. By using slightly longer primers, 18–24 nucleotides in size, than the traditional primers used for such analysis, more reliable RAPD results were obtained. 15 primers gave rise to amplified bands, and the results could be grouped into two categories. The patterns of amplified products produced by 12 primers, group A, were polymorphic. These results were analyzed using a NTSYS-PC (Numerical Taxonomy and Multivariate Analysis System), and a dendrogram grouping the four local cultivars was produced. The three primers of group B gave rise to a monomorphic band pattern from four local garlic clutivars, indicating that these primers possibly recognize garlic specific sequences. These primers were useful in identifying genetic variations among theAllium species.

Differential response ofAzolla microphylla kaulf. andAzolla filiculoides Lam. to sodium fluoride

Abstract: We assessed the differential response ofAzolla microphylla andAzolla filiculoides to fluoride stress by growing them in culture media containing 1 to 50 ppm sodium fluoride (NaF).A microphylla had a higher total chlorophyll content thanA. filiculoides. Both species showed gradual decreases in protein content as the concentration of NaF increased.A. microphylla accumulated less proline thanA. filiculoides when more NaF was added to the culture medium. For all concentrations tested, the amount of residual fluoride in the nutrient media that supportedA. microphylla was higher than in the nutrient media used for growingA. filiculoides.

Expression and regulation of theRSI-1 gene during lateral root initiation

Abstract: The tomato geneRSI-1 was previously identified as a molecular marker for auxin-induced lateral root initiation. We have further characterized the expression mode of theRSI-1 gene in tomato andArabidopsis thaliana. Northern blot analyses revealed that the gene was induced specifically by auxin in tomato roots and hypocotyls. For experiments with transgenic plants, the 5′ flanking region of theRSI-1 gene was linked to a GUS reporter gene, then transformed into tomato andArabidopsis. In these transgenic tomato plants, GUS activity was detected at the sites of initiation for lateral and adventitious roots. Expression of the fusion gene was auxin-dependent and tissue-specific. This was consistent with results from the northern blot analyses. In transgenicArabidopsis, the overall expression pattern of theRSI-GUS gene, including tissue specificity and auxin inducibility, was comparable to that in transgenic tomato seedlings. These results indicate that an identical regulatory mechanism for lateral root initiation might be conserved in both plants. Thus, the expression mode of theRSI-CUS gene inArabidopsis mutants defective in lateral root development should be investigated to provide details of this process.