June 1999, Volume 41 Issue 6

 

          Research Articles
A Preliminary Study on Direct Regeneration of Flower Buds from Peduncle Calli in Dracaena fragrans cv. massangeana
Author: LI Xue-Dong, CHANG Qing and LU Wen-Liang
Journal of Integrative Plant Biology 1999 41(6)
      
    Flower buds were directly regenerated from calli in vitro in the woody plant Dracaena fragrans cv. massangeana Hort. On modified MS medium supplemented with 1.0 mg/L 6-BA and 1.0 mg/L IBA, two kinds of calli, A and B, were formed from the peduncle explants cultured for 5 months. Calli A were loose and on their surface there were many irregular granule-like structures (GLC); Calli B were compact and had bigger tumor-like structures (TLC) on their surface. When the GLC and TLC were transferred onto the medium respectively with 0.4 mg/L 6-BA and 1.0 mg/L IBA, flower buds were differentiated directly from the GLC but only vegetative buds and roots were differentiated from the TLC after culturing for 4 weeks. The GLC could be partly transformed into TLC in the continuous passage culture. Assays on hormones revealed that at a fixed IBA concentration of 0.4 mg/L the defferentiation frequency of flower budding was increased as the 6-BA concentration was decreased from 2.0 mg/L to 10 mg/L. Alternatively, at a fixed 6-BA concentration of 2.0 mg/L, the flower budding frequency was increased when the IBA concentration was changed from 0.4 mg/L to 1.0 mg/L. Moreover, the addition of 2.0 mg/L zeatin to the culture medium containing 2.0 mg/L 6-BA and 0.4 mg/L IBA was favorable to the regeneration of the flower buds. Nevertheless supplementing 1.0 mg/L GA3 into the medium on which the calli had differentiated into flower buds, the flower buds would gradually wither after 2 weeks in culture.
Abstract (Browse 1926)  |  Full Text PDF       
Effects of Salicylic Acid and Aspirin on the ATP Contents in Wheat Seedlings Under NaCl Stress
Author: ZHANG Shi-Gong, GAO Ji-Yin and SONG Jing-Zhi
Journal of Integrative Plant Biology 1999 41(6)
      
    Four wheat ( Triticum aestivum L. ) genotype, "Chinese Spring", "Nongda 85021" (salt sensitive genotypes) and "Chadianhong", "Dong 68"( salt resistant genotypes) seedlings under NaC1 stress were involved. The results showed that, exogenous salicylic acid and aspirin relatively increased the ATP content in wheat seedlings under NaC1 stress, and the increasing range of root was larger than that of shoot, not only in the salt sensitive genotypes but also in the salt resistant genotypes. This suggests that an energy balance is maintained in wheat seedlings under NaC1 stress.
Abstract (Browse 1933)  |  Full Text PDF       
Isolation and Cytological Observation of Viable Sperm Cells of Rice
Author: GOU Xiao-Ping, WANG Sheng-Hua and CHEN Fang
Journal of Integrative Plant Biology 1999 41(6)
      
    Sperm cells of rice ( Oryza sativa L. ) were isolated from mature pollen grains near anthesis using osmotic shock with sucrose solution. They were separated from pollen contaminants by a Percoll gradient centrifugation. Isolated sperm cells were viable as tested with the fluorochromatic reaction. Cytological observations revealed that the two sperm cells just released from a pollen grain were linked together and each had a long tail-like extension. The isolated sperm cells were spherical with irregular surface and most of them separated, but some still remained in pairs that connected by finger-like structure. As observed with TEM, the isolated sperm cell was surrounded by a single plasma membrane and cell wall did not exist. Sperm nucleus was large and euchromatic.
Abstract (Browse 1763)  |  Full Text PDF       
Genetic Diversity and Geographic Variation in Natural Populations of the Endemic Castanea Species in China
Author: LANG Ping and HUANG Hong-Wen
Journal of Integrative Plant Biology 1999 41(6)
      
    Genetic variability in 30 populations of three endemic Castanea (Tourn.) L. species (C. moUissima BI., C. seguinii Dode. and C. henryi (Skan) Rehd. et Wils. ) in China was investigated using isoelectric focusing in thin-layer polyacrylamide slab gels at 20 loci coding for 12 enzyme systems. C. mollissima was found to possess a significant higher value of genetic variability than that of the other two species. The percentage of polymorphic loci (P) and the expected heterozygosity (He) were 90.0% and 0. 311 at the species level, respectively; while P = 84.7 %, He = 0.295 at the population level. Comparison of the population genetic variability of C. mollissima in three regions of China, the populations from the Yangtze River valley showed a markedly higher mean expected gene heterozygosity. The results provided additional evidence that the Yangtze River valley, particularly in Shennongjia area, was the center of the genetic diversity of C. moUissima. Genetic relationships among populations and species were assessed by Nei genetic identity (I) and standard genetic distance (D), suggesting that C. mollissima and C. seguinii have a closer relationship, and genetic distances were correlated with geographical distances among populations. Genetic differentiation between populations in C. mollissima, C. seguinii and C. henryi was 7.5%, 10.9% and 22.1%, respectively, and the gene flow rate (Nm) was 3.20, 2.05 and 0.88 respectively. The study provides useful imfonnation for understanding of the origin and evolutionary events in genus Castanea and planning an effective conservation strategy.
Abstract (Browse 1822)  |  Full Text PDF       
Research on Succession Model FOROAK of Mongolian Oak Korean Pine (Quercus mongolica-Pinus koraiensis) Forest
Author: SANG Wei-Guo, CHEN Ling-Zhi and MA Ke-Ping
Journal of Integrative Plant Biology 1999 41(6)
      
    Based on forest dynamics theory, gap model FOROAK was developed for simulating long-termdynamics of Mongolian oak (Quercus rnongolica Fisch. )-Korean pine (Pinus koraiensis Sieb. et Zucc. )forest. The model included two parts: biological growth and environmental impacts on growth. Different areapatches were used in simulating forest changes. The results showed that this forest gap was 0.05 hm2. Themodel testing demonstrated that it could reasonably simulate forest dynamic process, and had a very highaccuracy to predict species compositions. The observed species basal areas was similar to the predicted at 60,100 and 270 year forests, the observed species compositions were similar to the predicted at old forest period.Complex changes were found through modeling forest dynamics of bare ground. Mongolian oak and white birch( Betula platyphylla Sukacz. ) dominated at early stage, forest dominated by broad leaved species was formedat middle stage, and then Korean pine dominated at latter stage. The prediction of current primary forestshowed that it was steady during the next 300 year period, the number of trees and the biomass of Korean pine changed very little.
Abstract (Browse 1954)  |  Full Text PDF       
Study on the CO2 release Rate of Soil Respiration and Litter Decomposition in Stipa grandis Steppe in Xilin River Basin, Inner Mongolia
Author: CHEN Si-Qing, CUI Xiao-Yong, ZHOU Guang-Sheng and LI Ling-Hao
Journal of Integrative Plant Biology 1999 41(6)
      
    Based on the measurement of the CO2-release rate of soil respiration and litter decomposition in Stipa grandis Smim steppe in Xilin River Basin, Inner Mongolia, the authors analyzed the seasonal dynamic pattern of soil respiration and litter decomposition and their relation to the aboveground biomass, belowground biomass and environmental factors. The results were as follows: (1) The seasonal dynamic pattern fit nearly a trapezoidal curve and the highest CO2-release rate appearing in the late August was 2.51 gCm-2d-l; (2) The seasonal dynamic pattern of CO2-release rate was generally consistent with that of the aboveground biomass, especially with the green aboveground biomass, but was not consistent with or even contrary to that of the belowground biomass; (3) The litter layer on the soil surface could slow down the emission of CO2 from soil to atmosphere; (4) The soil moisture (x) was highly correlated with the CO2-release rate (y), which could be described by a logarithmic regression model: y = 3.4691og10x-2.053 (r = 0.92, P < 0.01).
Abstract (Browse 1976)  |  Full Text PDF       
Screening of Salt Tolerant Watercress Variants on Natural Seawater Contained Medium
Author: DU Li-Qun, LI Yin-Xin, LI Hong-Jie, GUO Bei-Hai, ZHU Zhi-Qing and ZHOU Bai-Cheng
Journal of Integrative Plant Biology 1999 41(6)
      
    The responses of stem segments of watercress ( Nasturtium offtcinale R. Br. ) to 6-BA, NAA and 2,4-D were studied. MS medium supplemented with 2.0 mg/L 6-BA, 0.2 mg/L 2,4-D was used for callus initiation and maintainance. MS medium supplemented with 4.0 mg/L 6-BA was suitable for plant regeneration and MS medium without plant hormone supplement was used for rooting and plant propagation. For screening of salt. tolerant calli, stem segments of watercress were plated onto callus initiation medium containing 1/3 natural seawater. Seventeen out of the 325 plated explants produced calli. The growth curves demonstrated that the growth rate of salt-tolerant calli on saline medium almost matched that of the control calli on normal medium. Some of the salt-tolerant calli were transferred to the normal regeneration medium or saline regeneration medium to induce plant regeneration. In the first case, buds and shoots were regenerated in the same way as those of control calli on normal regeneration medium. More than 1 000 regenerated shoots were obtained of which 83 regenerated shoots were cut and transferred to saline MS base medium. At first, all shoot growth was inhibited, but 40 days after the transfer, rapid-growing axillary shoots were observed on 16 of the original shoots but none on the control shoots on saline MS base medium. Moreover, green spots appeared on most calli 10 days after they were transferred to saline medium, however buds appeared only on 5 calli from the 30 transferred calli and at the end only 2 rapid-growing shoots were obtained from two calli. In total, 18 variant lines were obtained through propagation of the salt-tolerant shoots on saline MS base medium. RAPD analysis was performed in 10 of the 18 salt-tolerant variant lines and DNA variation was detected in all the tested variant lines.
Abstract (Browse 2214)  |  Full Text PDF       
Partial Purification of the Plasma Membrane H+ ATPase from Wheat Roots
Author: QIU Quan-Sheng and SU Xue-Feng
Journal of Integrative Plant Biology 1999 41(6)
      
    The plasma membrane vesicles were purified from wheat (Triticum aestivum L. ) roots by the sucrose gradient centrifugation methods. Partially purified plasma membrane H+ -ATPases from wheat roots were prepared from the plasma membrane vesicles by a process including Triton X-100 and KC1 treatment, Zwittergent 3-14 solubilization and ammonium sulfate precipitation. The specific activity of H+ -ATPase was increased gradually during purification, and an 8.4 folds increase in ATPase activity was finally obtained. SDS-PAGE showed that the polypeptide of 94 kD was accumulated during the purification and a final content of 15.7 folds increased after the purification. The results indicated that the partially purified plasma membrane H + -ATPases were stimulated by K+ and inhibited by vanadate and N, N'-dicyclohexylcarbodiimide; however, they were not inhibited by NaN3, NaNO3 and Na2MoO4.
Abstract (Browse 1842)  |  Full Text PDF       
Effects of Elevated CO2 and High Temperature on Single Leaf and Canopy Photosynthesis of Rice
Author: LIN Wei-Hong, BAI Ke-Zhi and KUANG Ting-Yun
Journal of Integrative Plant Biology 1999 41(6)
      
    The increase of atmospheric CO2 concentration is indisputable. In such condition, photosynthetic response of leaf is relatively well studied, while the comparison of that between single leaf and whole canopy is less emphasized. The stimulation of elevated CO2 on canopy photosynthesis may be different from that on single leaf level. In this study, leaf and canopy photosynthesis of rice ( Oryza sativa L. ) were studied throughout the growing season. High CO2 and temperature had a synergetic stimulation on single leaf photosynthetic rate until grain filling. Photosynthesis of leaf was stimulated by high CO2, although the stimulation was decreased by higher temperature at grain filling stage. On the other hand, the simulation of elevated CO2 on canopy photosynthesis leveled off with time. Stimulation at canopy level disappeared by grain filling stage in beth temperature treatments. Green leaf area index was not significantly affected by CO2 at maturity, but greater in plants grown at higher temperature. Leaf nitrogen content decreased with the increase of CO2 concentration although it was not statistically significant at maturity. Canopy respiration rate increased at flowering stage indicating higher carbon loss. Shading effect caused by leaf development reached maximum at flowering stage. The CO2 stimulation on photosynthesis was greater in single leaf than in canopy. Since enhanced CO2 significantly increased biomass of rice stems and panicles, increase in canopy respiration caused diminishment of CO2 stimulation in canopy net photosynthesis, keaf nitrogen in the canopy level decreased with CO2 concentration and may eventually hasten CO2 stimulation on canopy photosynthesis. Early senescence of canopy leaves in high CO2 is also a possible cause.
Abstract (Browse 1865)  |  Full Text PDF       
Physiological Mechanisms of Growth inhibition by Concentrated Potassium in Dunaliella Salina
Author: LIU Pei-Ran and WU Wei-Hua
Journal of Integrative Plant Biology 1999 41(6)
      
    It was observed in our preliminary experiments that the growth of Dunaliella salina (Dunal) Teed. cultured in medium containing 1 mol/L NaC1 was almost completely inhibited by the addition of 100 mmol/L KC1. This study was focused on elucidating the physiological mechanisms by which high K+ inhibits D. salina growth. Under the control conditions, the pH of the medium rapidly increased from 8 to 10 along with the growth of D. salina. However, addition of 100 mmol/L KCI significantly inhibited the increase of medium pH. The results suggested that the growth of D. salina may require a low environmental of H + concentration or be related to the H + transport into the D. salina cells. Interestingly, D. salina cultured in various media with different pH buffered with 40 mmol/L Tris-HC1 (or Tris-NaOH) did not show any significant difference in the growth rates. This result brings up the question on the previous hypothesis that Na+/H+ antiport plays a major role in Na + extrusion in D. salina. The photosynthetic rate of D. salina was not inhibited immediately following the addition of high K+ in the reaction medium, but it was significantly inhibited after the pretreatment of algae with high K+ for 12 hours or longer. The results from simultaneous measurements of O2 evolution of D. salina and the changes in pH of the medium revealed that the inhibitory effect of high K + on D. salina growth was somehow associated with K+ effect on pH changes in the medium. The high K+ treatment of D. salina also resulted in significant decrease of chlorophyll contents in the algae. It is concluded that the inhibitory effects of high K + on photosynthesis of D. salina may, at least partially, account for the growth-inhibition of D. salina growth by high K+; the inhibitory effects of high K+ on D. salina photosynthesis may result from the influence of K + on H + transport across the plasma membranes of D. salina cells.
Abstract (Browse 1907)  |  Full Text PDF       
Conditional Selection of the Extraction and Isolation of ABA Binding Protein(s) from Vicia faba Abaxial Epiderm
Author: WU Zhong-Yi, JIA Wen-Suo and ZHANG Da-Peng
Journal of Integrative Plant Biology 1999 41(6)
      
    The abaxial epiderm of Vicia faba L. was chosen to prepare the crude extract of ABA binding protein (ABA-BP). The activity of ABA-BP was dependent on different extraction methods. The specific binding capacity of ABA-BP extracted with 0.5% Triton X-100 (binding activity (B) = 0. 487 nmoL/g protein) was higher than that with extracted cold acetone (0. 325 nmol/g protein) or (NH4)2SO4(0. 223 nmol/ g protein). The activity duration of ABA-BP extracted with Triton X-100 (60% Bmax after 40 h) was longer than that with cold acetone (30% Bmax after 10 h). The ABA-BP activity of binding ABA was sensitive to pH change with an optimum pH of 6.5. The ABA-BP specific binding activity decreased quickly under high concentration of NaC1 ( > 300 mmoL/L), but increased 12% with 5 mmol/L KC1. Some divalent cations like Ca2+ and Mg2 + were required for enhancing the ABA-BP activity. These optimum conditions are primordial for ABA-BP purification.
Abstract (Browse 1867)  |  Full Text PDF       
Effects of Rewatering on Light Harvesting Chlorophyll a/b Protein Complex of Photosystem in Zea mays
Author: HAO Li-Min, WANG Hong-Liang and LIANG Hou-Guo
Journal of Integrative Plant Biology 1999 41(6)
      
    The amount and conformation of light-harvesting chlorophyll a/b-protein complex (LHC ) of photosystem II and the expression of a gene encoding for LHC were investigated when maize ( Zea mays L. ) seedlings were exposed to water stress and rewatering. The relative water content (RWC) and water potential in maize leaves decreased markedly after 72 h of water stress; the content of chlorophyll and apoproteins of LHC and the mRNA level of a gene encoding for LHC were reduced pronouncedly, but not recovered after 24 h of rewatering. However, the conformation of LHC in thylakoids was also altered by water stress but could be recovered by 24 h of rewatering. The authors proposed that two ways of dissipating relattive excess excitation energy may be encountered in the photosynthetic membrane. A fast way is by changing the conformation of LHC and another relatively slow way is the reduction of components of LHC , through which the reduction of apoproteins of LHC can be regulated partly at the transcript level.
Abstract (Browse 1732)  |  Full Text PDF       
Cloning and Analysis of AtJ3 Gene in Arabidopsis thaliana
Author: ZHOU Ren-Gang and Jan A. MIERNYK
Journal of Integrative Plant Biology 1999 41(6)
      
    The nucleotide sequence of a cDNA clone from Arabidopsis thaliana (L.) Heynh. "ecotype Columbia" was determined. The open reading frame encoded a protein, AtJ3, which was highly homologous to DnaJ protein of E. coli. The predicted amino acid sequence of AtJ3 contained J-domain, G or GFdomain, Cysteine-rich Zn finger-like sequence, which were all characteristic of this class of DnaJ homologues. And the C-teminal of At J3 was -CAQQ, a farnesylation motif. Using primers based on the cDNA, the corresponding gene AtJ3 was isolated and sequenced. The structure of this gene consisted of six exons interrupted by five introns. The results of Southern analysis indicated that AtJ3 was a single structure gene. At J3 was censtitutively expressed in cotyledons, leaves, roots, flowers, and siliques based on Northern analysis. Heat shock at 32 led to increase in mRNA expression in leaves.
Abstract (Browse 1909)  |  Full Text PDF       
Study on Genomic Changes in Partial Amphiploids of Common Wheat Wheatgrass
Author: LIU Bao, HE Meng-Yuan and HAO Shui
Journal of Integrative Plant Biology 1999 41(6)
      
    According to conventional theory, little genomic changes should occur in homozygous and stable amphiploids of the grass family, particularly those involving polyploid wheat as a parent. In the present study, however, extensive genomic changes were detected in two octoploid partial amphiploids of common wheat ( Triticum aestivum L. )-wheatgrass ( Agropyron intermedium (Host) P.B. = Elytrigia intermedia (Host) Nevski = Thinopyrum intermedium (Host) Barkworth and Dewey), namely Zhong 3 and Zhong 5, by RFLP an, analysis using 10 low-copy, wheat chromosome-specific sequences and 33 representative homoeologous group-specific sequences as probes. C, enomic changes involved loss of wheat hybridization fragment (s) and/or acquisition of new fragment(s). Uniformity of the RFLP patterns among 5 individual plants taken respectively from Zhong 3 and Zhong 5 in two successive generations, suggested that genomic changes probably had occurred in the early few generations after octoploid amphiploid formation, and remained essentially static thereafter, The highly similar RFLP patterns between Zhong 3 and Zhong 5, which had identical genomic constitution but differed from each other due to involvement of different wheat varieties as parents imply that genomic changes were probably not at random. Possible causes for the extensive and rapid genomic changes in the newly formed plant amphiploids, as well as their implications for polyploid genome evolution and breeding application are discussed.
Abstract (Browse 1817)  |  Full Text PDF       
Molecular Evidence of a Pair of PCR Primer for Rye 1R Chromosome Specificity
Author: WANG Er-Ming, XING Hong-Yan, ZHANG Wen-Jun, WEN Yu-Xiang and WEI Rong-Xuan
Journal of Integrative Plant Biology 1999 41(6)
      
    Based on the differences of rRNA intergenic sequences between wheat ( Triticum aestivum L. ) and rye ( Secale cereale L. ), rye specific primer set NOR-R1 was synthesized according to Koebner' design. PCR analyses were carried out on different DNA substrates of common wheat and its relatives such as Agropyron elongataum (Host) Beauv., Haynaldia villosa Shur. and Hordeum vulgare L. The results confirmed that NOR-R1 primer set is specific to rye. It was found that PCR using DNAs from wheat materials containing 1R chromosome resulted in the specific amplification products of rye, whereas no amplification product was detected in PCR when using DNAs with other rye chromosomes. FISH (Fluorescent in situ Hybridization) further revealed that the binding sites for the primer set NOR-R1 were only on nucleolar organizing region of chromosome 1R. These results indicated that the primer set NOR-R1 provides a useful means for molecular tagging of rye chromosomes 1 R in wheat genetic background.
Abstract (Browse 1810)  |  Full Text PDF       
Virus Movement Protein Gene Mediated Resistance Against Cucumber Mosaic Virus Infection
Author: ZHANG Zhen-Chen, LI Da-Wei, ZHANG Lee, YU Jia-Lin and LIU Yi
Journal of Integrative Plant Biology 1999 41(6)
      
    Tobacco (Nicotiana tabactum L. ) "NC89" plants were transformed with deletion mutant of cucumber mosaic virus (CMV) movement protein (MP) gene and full-length CMV MP gene, respectively. The transformed plants were analyzed with polymerase chain reaction (PCR), PCR-Southem, Southern and Western blots. R0 generation of the transgenic plants were inoculated with CMV. Five out of 10 lines of tobacco plants (BMPK) transformed with CMV MP deletion mutant gene showed high resistance to CMV infection and remained symptomless for up to 50 days post-inoculation. In contrast, tobacco plants (BMPR) transformed with full-length CMV MP gene did not show resistance to CMV infection. However, most of the infected full-length CMV MP gene transgenic plants recovered by showing none or very mild mosaic symptoms in 40 days post-inoculation. The results of R1 generation of the BMPK transgenic plants tested under field conditions showed that all 5 lines of transgenic plants could delay the virus disease development.
Abstract (Browse 1786)  |  Full Text PDF       
A Study on the Leaf Structure of Four Reed Ecotypes
Author: ZHENG Wen-Ju, WANG Shuang and ZHANG Cheng-Lie
Journal of Integrative Plant Biology 1999 41(6)
      
    The leaf anatomy and uhrastructure of the vascular bundle sheath cells of four ecotypes of reed (Phragmites communis Trin. ) were observed with light and electron microscope. The four ecotypes were the swamp reed, dune reed, heavy salt meadow reed and the light salt meadow reed. It was shown that the intracellular content of the vascular bundle sheath cells of the swamp reed was lower than that of the dune reed; that of the heavy salt meadow reed was between that of the former two reeds and that of the light salt meadow reed and that of the light salt meadow reed was similar to the dune reed. The chloroplasts in the swamp reed were round-shaped with poorly developed grana. Starch grains were not visualized. The uhrastructure of their chloroplasts were similar to those in the typical C3 plants as wheat. By contrast, the chloroplasts in the vascular bundle cells of the dune reed were elliptical with their structure similar to that of the typical C4 plants as maize. These chloroplasts contained some poorly developed grana thykloid. The chloroplasts of the vascular bundle sheath cells in the heavy salt meadow reed were similar to those seen in the dune reed, however, those in the light salt meadow reed appeared to be beth round .and elliptical in shape. The above results suggested a great habitat variation did occur among the four ecotypes of reed in which these exists an obvious evolutional trend from C3 to C4 plants.
Abstract (Browse 2114)  |  Full Text PDF       
Structure Characteristics Associated with Salt Tolerance of Populus euphratica
Author: GU Rui-Sheng, JIANG Xiang-Ning and GUO Zhong-Chen
Journal of Integrative Plant Biology 1999 41(6)
      
    The characteristics of the cell and organ structures of Populus euphratica Oliv. in relation to salt and osmotic tolerance were compared with those of P. tomentosa Cart. in vitro under the electron and light microscopic observation. P. euphratica exhibited characteristic structure which was associated with salt stress. It had well-developed epidermis and exodermis in the root tip and poorly developed conducting tissue in leaf. Root hairs were formed closer to the root tips. AsP. euphratica were stressed with salt and PEG, more abundance of chondriosomes and plastids in the cytoplasm and more containing substance in the plastid were observed and the osmophilic substance was obviously displayed in the cytoplasm and in the posterior margin of the vacuole. The filamentous structure, bigger nucleus and nucleolus were visualized in the stressed suspension-cultured cells of P. euphratica. The meristemic cells in the root tip of P. euphratica could maintain their structure when the plant was subjected to 8 g/L NaCl stress. It was also demonstrated that the cell wall and plasmalemma of P. euphratica were tightly combined as a dentate form, explaining why the cell could endure severe salt or osmotic stress and resist to plasmolysis indicating that P. euphratica possesses a solid structure base as a defense to salt stress.
Abstract (Browse 1941)  |  Full Text PDF       
Recent Research Advances in Plant Small Nucleolar RNA
Author: ZHONG Ling and QU Liang-Hu
Journal of Integrative Plant Biology 1999 41(6)
      
    Eukaryotic cell contains diverse populations of metabolically stable small nucleolar RNAs (snoRNA). They are involved in many aspects of rRNA processing and maturation, snoRNAs have been identified in a wide range of eukaryotes and are presumed to be ubiquitous. Most of the snoRNAs characterized are from vertebrate and yeast, in which more than 130 species have been defined but only about 10 species of plant snoRNAs have been identified. The main reason may lie in the difficulties involved in different methodologies in isolating plant nuclei and nucleoli in appropriate amounts and purity for biochemical analysis. Although the study of plant snoRNA started later and the number of plant snoRNA is less, comparing with other eukaryotes, plant snoRNAs possess at least two distinct specific properties: (a) The way of snoRNA gene transcription. U3 is the first snoRNA discovered and identified in both vertebrate and plant. Plant U3 snoRNA gene promoters are clearly distinct from their yeast and mammamia counterparts, in beth the essential cis elements and the determinants of RNA polymerase specificity. The genes encoding the U3 snoRNA in plant are transcribed by RNA poi. , but all other organisms studied to date are by RNA Dol. 11. Plant U3 gene contains the conserved promoter elements USE and TATA, in a poi. -specific spacing. (b) The clusters of snoRNA genes. In animal and yeast, a large number of snoRNA are encoded within the introns of protein- ceding genes. The introns contain only single sonRNA gene and their processing involves exonucleolytic release of the snoRNA from debranched intron lariats. In contrast, some U14 genes and other snoRNAs, including box C/D and ACA families in plant, are found in clusters and are expressed polycistronically. And in the first intron of rice hsp70 gene, six snoRNAs, including box C/D and ACA families, closely linked together. How transcription of snoRNAs is coordinated with the expression of nueleolar or ribosomal proteins and the nature of the processing machinery remain to be elucidated. These differences from yeast and vertebrates, in snoRNA gene transcription and gene organization, imply the characteristic pathway of the evolution of the plant snoRNA genes.
Abstract (Browse 1757)  |  Full Text PDF       
Ultrastructural Study on the Degenerative Processes of Procambial Cells in Maize Leaf Blades
Author: OUYANG Xue-Zhi, XIE Shao-Ping and HE Zhu-Mei
Journal of Integrative Plant Biology 1999 41(6)
      
    Cell degeneration often occurred in Zea mays L. leaf procambium in various stages of development and could be classified either in the form of autolysis or condensation. In the autolytic degeneration the cells underwent a series of events from the appearance of prominant autophagie activity in the early stages, accompanied by a decrease of ribosomes and electron density of cytoplasm to the final stages of autolysis resulting in disorganization and disappearnce of all protoplasmic components, of which the nuclei and plasmalemma were the last to disappear. In the condensed type the initiation of cell degeneration was accompanied by an increase in the cytoplasmic density. As cell degeneration progressed, the protoplasmic components appeared to disintegrate and disappear in an orderly fashion i.e. dictyosomes and ER disorganized first, followed by plastids, nuclei and some mitochondria. The plasmalemma, ribosomes and mitochondria were still recognizable as the cell being crashed by the surrounding cells during the final stages of degeneration.
Abstract (Browse 2008)  |  Full Text PDF       
 

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