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.     

Tubercle bacilli generate a novel cell wall-associated pigment after long-term anaerobic culture

Many cases of tuberculosis result from reactivation of previously acquired latent infections. Models to study such persister forms often involve gradual depletion of oxygen during culture as poor aeration is a characteristic of non-progressive TB granulomas. Anaerobically cultured bacilli develop a thickened outer-most cell wall layer. Here, we analyzed this layer from anaerobically cultured Mycobacterium tuberculosis and Mycobacterium bovis BCG. By six weeks of anaerobiosis a pigment was detected at levels > 60-fold higher in anaerobic than aerobic bacilli. This pigment was responsible for the electron-dense appearance of the thickened cell wall layer and gave an electrospray mass spectrometry peak at 409 Da (M+Na)+ or (M+H)+. We termed this pigment APP1, anaerobically produced pigment 1, the first pigment identified in M. tuberculosis.     

Inflorescence bud proteins of Pistacia vera

 The Pistacia vera L. (common name pistachio) is a unique dioecious and deciduous tree species, which is productive under harsh desert climates. We have identified and purified an Inflorescence Bud Protein of 32 kDa (IBP32) from male pistachio trees. There is a close correlation between its accumulation and inflorescence bud development and its disappearance and flowering. Using antibodies raised against this protein, we have identified in female trees the IBP32 and in addition a 27 kDa protein (IBP27), which appears to be specific to female inflorescence buds. The accumulation and disappearance of IBP27 follows the same pattern as that of IBP32. These proteins are glycoproteins rich in glycine and alanine and are highly hydrophilic. Based on the analytical results and immunological cross-reactivity between dehydrin antibodies and the IBPs, it is assumed that the latter are dehydrin-like and may protect inflorescence bud meristems against cold injury during dormancy. The IBPs are the major proteins of the pistachio bud, therefore they may also serve as nitrogen storage during winter for inflorescence bud growth in spring. Received: 17 October 1997 / Accepted: 6 March 1998     

Recovery of plants from “Near-Lethal” stress

This study reports on the dieback and recovery of red-osier dogwood, Cornus sericea L. plants from near-lethal (NL, sublethal) stress after varying lengths of post-stress environment (PSE). Intact dormant stems were subjected to 47° C for one hour during either October, November or December, and then placed into either constant 0° C or 23° C (dark condition) or kept under natural conditions at Corvallis, OR. Plants exposed to NL-heat stress in October died prior to 9 weeks of 0° C PSE, while none of the plants from other PSE treatments showed signs of injury. For plants exposed to NL-heat stress during November and December, stemdieback occurred at 0° C after 12 and 15 weeks, respectively. None of the plants from the other PSE treatments were injured. Post-stress temperatures of 0° or 5° C following NL-heat in October were lethal while temperatures above 10° C allowed recovery. Post-stress exposure to 0° C injured excised stems within 48 h, whereas irreversible damage to whole plants occurred by two weeks. Dormant plants exposed in October to other stresses, e.g., freezing temperature and hydrogen cyanamide, at NL dosages showed that these stresses also caused plant dieback at 0° C and little or no dieback at 23° C PSE.Abbreviations NL Near-Lethal - PSE Post-Stress Environment     

Membrane turnover in imbibed dormant embryos of the wild oat (Avena fatua L.)

Germinating non-dormant (ND) embryos of wild oat incorporate [³H]glycerol into phospholipid, and a 250% increase in total extractable phospholipid occurs within 72 h. During germination, leveles of phosphatidyl inositol showed the greatest change, increasing approximately 5-fold.Imbibed dormant (D) embryos of the wild oat also incorporate [³H]gycerol into phospholipids, but there is no net synthesis. A continuous turnover of membrane phospholipids could be demonstrated in pulse chase experiments, and although the proportions of most phospholipids does not change, there was a decrease of 50% in phosphatidyl serine.The half-life of [³H]glycerol in the extracted phospholipids of D and ND embryos varies between 35 and 57 h, and in membrane fractions separated on sucrose density gradients the half-lives vary between 26 and 56 h.D embryos induced to germinate with GA and ND embryos in which germination is repressed by ABA show similar phospholipid changes to ND and D embryos respectively, with the exception that the proportion of phosphatidyl serine remained unchanged in the ND-ABA embryos.It is concluded that the continual turnover of membranes of imbibed dormant embryos is consistent with the maintenance of cellular integrity determining the longevity of the seed under natural conditions.Abbreviations D dormant - ND nondormant - ABA abscisic acid - GA gibberellic acid (GA₃)     

Cytochemieal Observation on Garlic Clove before and after Temperature-Modulated Break of Dormancy

Usually, garlic clove keeps itself in dormancy during summer months and tends to break their dormancy as the climate becomes cooler toward autumn. Prolonged storage of garlic clove under relatively high temperature is a good measure taken in practics to retain its dormancy and refrain from sprouting. In fact, if garlic is stored around 30 ℃, its dormancy can be extended to more than six months while its exposure to low temperature (4 ℃) for a short duration will eventualy break its dormancy. The Dormant release can be diagnosed in the upper epidermis by signs of nuclear disintegration and appearance of APase, ATPase and POase activities. The nuclei in dormant epidermal cells keep their characteristic round shape and in the central position of the cells which are devoid of the enzyme activities mentioned. In case the clove is kept in 30℃ over a year, partial disintegration of the cells evacuation of the constituents also take place, as clearly shown by numerous proteinaceous granules suspended in the interior and by “nuclear extrusion” across the intercellular boundary.     

Effects of Dormancy Regulating Chemicals on Innate and Salinity Induced Dormancy in the Invasive <Emphasis Type="Italic">Prosopis juliflora</Emphasis> (Sw.) DC. Shrub

The effect of different types and concentrations of dormancy regulating chemicals (DRCs) on innate and induced dormancy was evaluated under optimal germination conditions in the invasive Prosopis juliflora shrub. Lower concentrations of gibberellic acid (0.3 mM) and kinetin (0.05 mM) were more effective in enhancing germination % and rate at higher concentrations of NaCl, but the reverse was true for thiourea. None of the DRCs alleviated innate dormancy of P. juliflora. Germination % and rate decreased as salinity increased. Percent final germination of non-treated seeds was significantly reduced at 500 mM NaCl and virtually inhibited in 600 mM NaCl. Germination reduction in 500 mM NaCl was not alleviated by any of the DRCs, but inhibition induced at 600 mM NaCl was partially alleviated by all the DRCs. Gibberellic acid had a significantly greater effect than kinetin in alleviating germination inhibition. For restoration of saline soil through the use of P. juliflora, results suggest using DRCs, particularly gibberellic acid and thiourea, as a preseeding treatment can overcome the problem of reduced germination.     

The evolutionary ecology of seed germination of Arabidopsis thaliana: variable natural selection on germination timing

Germination timing of Arabidopsis thaliana displays strong plasticity to geographic location and seasonal conditions experienced by seeds. We identified which plastic responses were adaptive using recombinant inbred lines in a field manipulation of geographic location (Kentucky, KY; Rhode Island, RI), maternal photoperiod (14-h and 10-h days), and season of dispersal (June and November). Transgressive segregation created novel genotypes that had either higher fitness or lower fitness in certain environments than either parent. Natural selection on germination timing and its variation explained 72% of the variance in fitness among genotypes in KY, 30% in June-dispersed seeds in RI, but only 4% in November-dispersed seeds in RI. Therefore, natural selection on germination timing is an extremely efficient sieve that can determine which genotypes can persist in some locations, and its efficiency is geographically variable and depends on other aspects of life history. We found no evidence for adaptive responses to maternal photoperiod during seed maturation. We did find adaptive plasticity to season of seed dispersal in RI. Seeds dispersed in June postponed germination, which was adaptive, while seeds dispersed in November accelerated germination, which was also adaptive. We also found maladaptive plasticity to geographic location for seeds dispersed in June, such that seeds dispersed in KY germinated much sooner than the optimum time. Consequently, bet hedging in germination timing was favorable in KY; genotypes with more variation in germination timing had higher fitness because greater variation was associated with postponed germination. Selection on germination timing varied across geographic location, indicating that germination timing can be a critical stage in the establishment of genotypes in new locations. The rate of evolution of germination timing may therefore strongly influence the rate at which species can expand their range.     

Relationship between water content and afterripening in red rice

Reactions regulating seed dormancy can proceed at water contents which are probably too low to permit metabolic activity. The loss of dormancy via afterripening of red rice. ( Oryza sativa L.) seeds was examined as a representative case. Equilibration of seeds to various moisture contents showed that afterripening was most rapid at 6–14% moisture content (dry weight basis). Afterripening did not occur at > 18% moisture content and was severely inhibited at < 5% moisture content. Seed viability was greater than 95% for all treatments. Utilization of moisture isotherms to calculate water-binding enthalpy values identified the optimal afterripening range as approximately the boundary between water-binding region 1 and region 2. From these findings, it is suggested that afterripening may involve some oxidative reactions which are inhibited at lower water contents by the rising free-energy and at the higher side by metabolic reactions.     

Metabolic and structural responses of pine buds under climate chamber conditions

Scots pine ( Pinus sylvetris L.) plants, about 2 m high, were placed in controlled conditions for 2 weeks in January, April and November. During the experiments made in January, the conditions in the climate chambers simulated either a gradual or abrupt advancement of spring. In April they simulated either the advancement of the season or its reversal back to January. In November the plants were transferred to conditions that resembled spring. In January, pieces of buds collected at the end of the experiment were also fixed for electron microscope studies.
Isolation of the ribosomes and the determination of their in vitro translation capacity revealed that in January the response to environmental changes was evident. An increase in synthesized proteins was caused by a rise in the translation capacity of ribosome assemblies rather than by an increase in their quantity. The cellular ultras-structure changed in conformity with the changes characteristic of the spring. In April, the plants transferred to the climate chambers maintained their ability to synthesize proteins, but the buds were judged to be under stress. In November die ability of the buds to respond to environmental changes was retarded or inhibited.