Differential expression of <Emphasis Type="Italic">Histone H3</Emphasis> gene in tea (<Emphasis Type="Italic">Camellia sinensis</Emphasis> (L.) O. Kuntze) suggests its role in growing tissue

Histone proteins are integral part of chromatin and their expression is typically linked to DNA replication in the S phase of cell cycle. Histone H3 is one of the four histones, along with H2A, H2B and H4, which forms the eukaryotic nucleosome octomer core. Using differential display of mRNA and rapid amplification of cDNA ends (RACE), a full-length Histone H3.1 cDNA (CsH3) was isolated from tea leaves. The open reading frame consisted of 411 nucleotides and deduced amino acid sequence comprised of 136 amino acid residues. CsH3 shared 79-82% and 98% identity at nucleotide and amino acid sequences, respectively with Histone H3 isolated from other plant species. During active-growth period of tea, higher expression was observed in apical buds that decreased gradually with increasing age of the leaf. During dormancy season, the expression of CsH3 was severely down-regulated in all the leaves studied. CsH3 was found to be down regulated in response to drought stress and ABA treatment and up-regulated by GA(3) treatment. A positive association of CsH3 abundance with active cellular growth suggested its role in plant growth and development.     

Periodicity of response to abscisic acid in lateral buds of willow (Salix viminalis L.)

Aseptically cultured lateral buds of Salix viminalis L. collected from field-grown trees exhibited a clear periodicity in their ability to respond to exogenous abscisic acid (ABA). Buds were kept unopened by ABA only when the plants were dormant or entering dormancy. Short days alone did not induce bud dormancy in potted plants but ABA treatment following exposure to an 8-h photoperiod prevented bud opening although ABA treatment of buds from long-day plants did not. Naturally dormant buds taken from shoots of field-grown trees and cultured in the presence of ABA opened following a chilling treatment. In no cases were the induction and breaking of dormancy and response to ABA correlated with endogenous ABA levels in the buds.Abbreviations ABA abscisic acid - GA₃ gibberellic acid - HPLC high-performance liquid chromatography - LD long day - MeABA methyl ABA - PAR photosynthetically active radiation - SD short day     

梨树花芽休眠解除与活性氧代谢的关系

梨树(Pyrus bretschneideri Rehd.)自然休眠和休眠解除时,花芽的活性氧代谢发生变化.O2-·产生速率和H2O2的含量在休眠期间上升,在休眠后期下降.抗氧化系统中SOD活性在自然休眠期呈下降趋势,自然休眠结束活性上升.POD和CAT活性在自然休眠期上升.抗氧化物质AsA和GSH的含量随休眠进行而下降,休眠解除过程中重新升高.APX和GR的活性在休眠期间活性下降,休眠结束活性迅速上升.这些结果表明:花芽的休眠与活性氧的代谢有很大关系.     

Cell cycle regulation during growth-dormancy cycles in pea axillary buds

Accumulation patterns of mRNAs corresponding to histones H2A and H4, ribosomal protein genes rpL27 and rpL34, MAP kinase, cdc2 kinase and cyclin B were analyzed during growth-dormancy cycles in pea (Pisum sativum cv. Alaska) axillary buds. The level of each of these mRNAs was low in dormant buds on intact plants, increased when buds were stimulated to grow by decapitating the terminal bud, decreased when buds ceased growing and became dormant, and then increased when buds began to grow again. Flow cytometry was used to determine nuclear DNA content during these developmental transitions. Dormant buds contain G₁ and G₂ nuclei (about 3:1 ratio), but only low levels of S phase nuclei. It is hypothesized that cells in dormant buds are arrested at three points in the cell cycle, in mid-G₁, at the G₁/S boundary and near the S/G₂ boundary. Based on the accumulation of histone H2A and H4 mRNAs, which are markers for S phase, cells arrested at the G₁/S boundary enter S within one hour of decaptitation. The presence of a cell population arrested in mid-G₁ is indicated by a second peak of histone mRNA accumulation 6 h after the first peak. Based on the accumulation of cyclin B mRNA, a marker for late G₂ and mitosis, cells arrested at G₁/S begin to divide between 12 and 18 h after decapitation. A small increase in the level of cyclin B mRNA at 6 h after decapitation may represent mitosis of the cells that had been arrested near the S/G₂ boundary. Accumulation of MAP kinase, cdc2 kinase, rpL27 and rpL34 mRNAs are correlated with cell proliferation but not with a particular phase of the cell cycle.     

Physiological and Environmental Requirements for Poplar (Populus deltoides) Bark Storage Protein Degradation

In poplar (Populus deltoides Bartr. ex Marsh), a 32-kD bark storage protein (BSP) accumulates in the bark during autumn and winter and declines during spring shoot growth. We investigated the physiological and environmental factors necessary for the degradation of poplar BSP. Poplar plants were exposed to short-day (SD) photoperiods for either 28 or 49 d. Plants exposed to short days for 28 d formed a terminal bud but were not dormant, whereas exposure to short days for 49 d induced bud dormancy. BSP accumulated in bark of plants exposed to both SD treatments. The level of BSP declined rapidly when nondormant plants were returned to long days. BSP levels did not decline in dormant plants that were exposed to long-day (LD) conditions. If dormant plants were first treated with either low temperatures (0[deg]C for 28 d) or with 0.5 M H2CN2 to overcome dormancy and then returned to long days, the level of BSP declined. Removal of buds from non-dormant or dormant plants in which dormancy had been overcome inhibited the degradation of BSP in LD conditions. BSP mRNA levels rapidly declined in plants exposed to long days, irrespective of the dormancy status of the plants or the presence or absence of buds. These results indicate that the buds of poplars are somehow able to communicate with bark storage sites and regulate poplar BSP degradation. These results further support an association of BSP mRNA levels with photoperiod because short days stimulate BSP mRNA accumulation, whereas long days result in a decline of BSP mRNA abundance.     

Involvement of gibberellins in breaking bud dormancy in euphorbia crinkle mosaic virus-infected stem cuttings ofEuphorbia pulcherrima willd.

Euphorbia pulcherrima, an ornamental plant, exhibits severe systemic viral infection. It grows vegetatively during summer and is dormant in winter. During the dormant period the buds on healthy stem cuttings remained dormant or rarely formed cyathia while the buds on virus-infected stem cuttings grew into leafy shoots and never became dormant. Quantitative estimation has revealed that breaking of bud dormancy in virus-infected stem cuttings may be regulated by markedly higher GA-like activity in them throughout the period than in their corresponding healthy stem cuttings.     

Change in plasma membrane ATPase activity during dormancy release of vegetative peach-tree buds

Plant dormancy and dormancy breaking depend, at least partially, on peculiar short distance relationships between buds and tissues underlying buds (bud stands). In peach-tree, it was previously observed that dormancy was related to a high nutrient absorption capacity in tissues underlying buds. This situation could be linked to higher plasma membrane ATPase activity (EC 3.6.1.3), inducing a higher nutrient absorption, in bud stands. This work consists of characterization of the plasma membrane ATPase activity in vegetative buds and bud stands during the rest period and dormancy release. During the dormant period (October and November), plasma membrane ATPase activity was found to be higher in bud stands than in buds. This was correlated with a lower amount of plasma membrane ATPase in buds compared to bud stands during this period. Moreover, plasma membrane ATPase activation by trypsin treatment was not the same in both tissues and different levels of ATPase activation could be noted within the same tissue during the different stages of dormancy release. According to these results, it can be postulated that dormancy release in peach-tree, is related to modifications of plasma membrane ATPase properties in buds and bud stands during winter time.     

Changes in Protein Interactions of Cell Cycle-Related Genes during the Dormancy-to-Growth Transition in Pea Axillary Buds

Apical dominance is a phenomenon in which a terminal bud growspredominantly and the growth of the axillary buds is suppressed.Here, we investigated the molecular mechanisms associated withcell cycle control that occur in pea axillary buds as a resultof decapitation. Proliferating cell nuclear antigen (PCNA) proteinwas detected in both dormant and growing buds, while PCNA mRNAwas absent in dormant buds. Pissa;CycBl;2 and Cdc2 proteinswere undetectable during dormancy. To analyze an interactionbetween PCNA and Pissa;CycD3;l, we performed anti-PCNA immunoaffinitycolumn chromatography. Pissa;CycD3;l protein was detected inthe eluate prepared from the dormant buds, but not in the eluateprepared from the growing buds. Furthermore, we performed anti-Pissa;CycD3;limmunoaffinity column chromatography. PCNA protein was detectedin the eluate prepared from the dormant buds, but not in theeluate prepared from the growing buds. These results indicatedthat PCNA associated with Pissa;CycD3;l only during dormancy.In addition, the interaction between PCNA and Pissa;CycD3;lwas confirmed by a yeast two-hybrid system. (Received April 8, 1998; Accepted August 5, 1998)     

Relation of polyamine biosynthesis to the initiation of sprouting in potato tubers

The polyamines putrescine, spermidine, and spermine and their biosynthetic enzymes arginine decarboxylase, ornithine decarboxylase and S-adenosyl-l-methionine decarboxylase are present in all parts of dormant potato (Solanum tuberosum L.) tubers. They are equally distributed among the buds of apical and lateral regions and in nonbud tissues. However, the breaking of dormancy and initiation of sprouting in the apical bud region are accompanied by a rapid increase in ornithine decarboxylase and S-adenosyl-l-methionine decarboxylase activities, as well as by higher levels of putrescine, spermidine, and spermine in the apical buds. In contrast, the polyamine biosynthetic enzyme activities and titer remain practically unchanged in the dormant lateral buds and in the nonbud tissues. The rapid rise in ornithine decarboxylase, but not arginine decarboxylase activity, with initiation of sprouting suggests that ornithine decarboxylase is the rate-limiting enzyme in polyamine biosynthesis. The low level of polyamine synthesis during dormancy and its dramatic increase in buds in the apical region at break of dormancy suggest that polyamine synthesis is linked to sprouting, perhaps causally.     

Metabolic changes in cherry flower buds associated with breaking of dormancy in early and late blooming cultivars

Changes of metabolic activities during dormancy and breaking of dormancy in the cherry flower buds of early blooming (EB) cultivar ( Prunus avium L. cv. Coeur de Pigeon) and late blooming (LB) cultivar ( Prunus serrulata Lindl. cv. Kwanzan) were determined. The LB buds had higher polyamines, protein and 1-(malonylamino) cyclopropane-1-carboxylic acid (MACC) content than the EB buds. During the dormant state, the DNA, RNA, protein and polyamines in the EB buds were low but increased slowly and steadily, whereas those in the LB buds remained at a consistently higher level. The transition from dormancy to the active state in both cultivars was characterized by a sharp increase in DNA, RNA, protein, polyamines, S-adenosyl-methionine (SAM), 1-aminocyclopropane-1-carboxylic acid (ACC) and MACC. After initial swelling and development of flowers, the levels of all these components decreased. Polyamine and ethylene biosyntheses did not seem to be competing for their common substrate, SAM, during flower bud development.     

Effect of growth regulators on proton transport through cytoplasmic membrane of potato tuber cells

Effects of the growth regulators epibrassinolide-694 (EB), gibberellic acid (GA), and abscisic acid (ABA) on the ATP-dependent translocation of H+ through the membranes of plasma membrane vesicles of potato (Solanum tuberosum L.) tuber cells were studied. The ATP-dependent accumulation of H+ in the plasma membrane vesicles from dormant tubers was inhibited by EB and ABA and stimulated by GA. After the break of dormancy, the stimulatory effect of GA increased, the inhibitory effect of ABA decreased, and EB stimulated the accumulation of H+ in the vesicles. The data suggest that the plasma membrane H+ ATPase is a target of phytohormones that regulate the dormancy of potato tubers.     

In Vitro Regeneration of Mat Sedge (Cyperus pangorei Rottb)

An in vitro protocol was developed for regeneration of Cyperus pangorei that may supplement enough raw materials for the mat weaving community. Callus was initiated from inflorescence explants on Murashige and Skoog’s (MS) medium supplemented with 5 and 10 μM each of 2, 4-D, 2, 4, 5-T and CPA. Development of numerous de novo spikelets from immature inflorescence explants grown in (10 μM) 2, 4, 5-T was observed. MS with 5 μM Kn and 100 ml l^?1 Coconut milk (CM) promoted shoot regeneration from calli. Calli from 2,4-D and CPA medium sub-cultured on medium containing 5 μM BAP, 5 μM Kn, 1 μM IAA and 100 ml l^?1 CM produced extensive and rapid rhizogenesis with wiry and scaly roots. Micropropagation using rhizome buds on MS medium with BAP, Kn and Zeatin at 10 μM concentrations resulted in shoot release and multiplication by breaking the bud dormancy. An average of 10 shoots per explant was produced in 10 μM BAP, whereas (10 μM) Kn and (10 μM) Zeatin induced only single shoot formation. The shoots were transferred to rooting media comprising 10 μM IAA with 1 μM BAP or Kn and then acclimatized. The results accomplished were found to be useful in developing a complete in vitro regeneration protocol towards the mass production of Cyperus species, which may provide a basis for further genetic improvements that may prove its use as an alternative natural fibre resource in commercial applications.     

Breaking the apple embryo dormancy by nitric oxide involves the stimulation of ethylene production

Mature seeds of apple (Mallus domestica Borb. cv. Antonówka) are dormant and do not germinate unless their dormancy is removed by several weeks of moist-cold treatment. We investigated the effect of short-term (3 h) nitric oxide (NO) pretreatment on breaking of apple embryonic dormancy expressed as inhibition of germination and morphological abnormalities of young seedlings. Imbibition of embryos isolated from dormant apple seeds with sodium nitroprusside (SNP) or S-nitroso,N-acetyl penicillamine (SNAP) as NO donors resulted in enhanced germination. Moreover, NO treatment removed morphological abnormalities of seedlings developing from dormant embryo. The NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-teramethylimidazoline-1-oxyl-3 oxide (cPTIO) removed the above effects. NO-mediated breaking of embryonic dormancy correlated well with enhanced ethylene production. Inhibitor of ethylene synthesis (AOA) reversed the stimulatory effect of NO donors on embryo germination. Additionally SNP reduced embryo sensitivity to exogenously applied ABA ensuing dormancy breakage. We can conclude that NO acts as a regulatory factor included in the control of apple embryonic dormancy breakage by stimulation of ethylene biosynthesis.     

Stamen development and winter dormancy in apricot (Prunus armeniaca)

Background and Aims

In temperate woody perennials, flower bud development is halted during the winter, when the buds enter dormancy. This dormant period is a prerequisite for adequate flowering, is genetically regulated, and plays a clear role in possibly adapting species and cultivars to climatic areas. However, information on the biological events underpinning dormancy is lacking. Stamen development, with clear differentiated stages, appears as a good framework to put dormancy in a developmental context. Here, stamen developmental changes are characterized in apricot (Prunus armeniaca) and are related to dormancy.

Methods

Stamen development was characterized cytochemically from the end of August to March, over 4 years. Developmental changes were related to dormancy, using the existing empirical information on chilling requirements.

Key Results

Stamen development continued during the autumn, and the flower buds entered dormancy with a fully developed sporogenous tissue. Although no anatomical changes were observed during dormancy, breaking of dormancy occurred following a clear sequence of events. Starch accumulated in particular places, pre-empting further development in those areas. Vascular bundles developed and pollen mother cells underwent meiosis followed by microspore development.

Conclusions

Dormancy appears to mark a boundary between the development of the sporogenous tissue and the occurrence of meiosis for further microspore development. Breaking of dormancy occurs following a clear sequence of events, providing a developmental context in which to study winter dormancy and to evaluate differences in chilling requirements among genotypes.     

Studies in Wild Oat Seed Dormancy: I. THE ROLE OF ETHYLENE IN DORMANCY BREAKAGE AND GERMINATION OF WILD OAT SEEDS (AVENA FATUA L.)

Seed of Avena fatua were shown to exhibit a characteristic loss of dormancy during dry storage at 25 C, whereas similar seed stored at 5 C maintained dormancy. 2-Chloroethylphosphonic acid was shown to increase germination of partly dormant seed imbibed under certain temperature regimes; a similar effect could not be established for fully dormant or fully nondormant seed. Using gas-liquid chromatography, natural ethylene levels were followed during imbibition of fully dormant and nondormant seed. A large peak in production was observed in the period prior to radicle emergence in the case of the nondormant seed. Measurements of ethylene production taken at 15 C, following periods of after-ripening in moist soil at either 5 or 25 C, indicated that endogenous production was unlikely to be a main cause of dormancy breakage in this species. The possibility that endogenous ethylene could play a role in natural dormancy breakage in aged seeds is discussed. The practical possibilities of 2-chloroethylphosphonic acid as a dormancy breaking agent in a field situation are outlined.