Biomedical subjects

J D Bewley

Publications and source records attributed to J D Bewley.

At least 37 records · Page 2Linked to original sources

PubMed1985

Reprogramming of Protein Synthesis from a Developmental to a Germinative Mode Induced by Desiccation of the Axes of Phaseolus vulgaris.

Immature seeds of Phaseolus vulgaris cv Taylor's Horticultural removed from the pod at 32 days of development do not germinate unless first subjected to desiccation. Our results show that premature drying not only redirects metabolism from a developmental to a germination program but it does so permanently, thus effecting an irreversible switch. This is shown by in vitro protein synthesis, and analysis of poly(A)(+) mRNA with a cDNA probe specific for phaseolin message. For example, the pattern of proteins synthesized in vitro by the mRNA fraction from fresh and prematurely dried axes show strong similarities; on the other hand, the mRNA population from rehydrated axes code for a different set of proteins. Also, the message for phaseolin is preserved following the normal maturation process and premature desiccation of seeds. Following rehydration of immature seeds at the desiccation-tolerant stage, this message is no longer detectable in the axes.

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PubMed1984

Plant Desiccation and Protein Synthesis. IV. RNA Synthesis, Stability, and Recruitment of RNA into Protein Synthesis during Desiccation and Rehydration of the Desiccation-Tolerant Moss, Tortula ruralis.

Upon rehydration of desiccated Tortula ruralis, RNA synthesis is immediately resumed; this resumption is quicker in moss recovering from slow drying than from rapid drying. Newly synthesized RNA enters the protein synthetic complex almost immediately upon rehydration, reaching control steady state levels within 2 hours after slow drying and 6 hours after rapid drying. RNA synthesized in the 1st hour following the readdition of water enters into polysomes much earlier after slow drying than after rapid drying. The RNA components of the protein synthetic complex are stable to desiccation at either slow or rapid speeds, although more so following the former drying regime. Immediately upon rehydration, these conserved RNA are readily utilized for protein synthesis, and continue to be so at least 4 hours thereafter. Hence, the speed of desiccation affects the rate at which RNA is synthesized upon subsequent rehydration, as well as the mode of utilization of that RNA.

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PubMed1984

Synthesis of the crystalloid protein complex in vivo in the endosperm of developing castor bean seeds.

The synthesis of subunit polypeptides of the crystalloid protein complex has been examined in endosperm from developing castor bean (Ricinus communis L. cv Hale) seeds. Pulse-label and -chase studies in vivo have shown that synthesis initially involves the formation of high molecular weight precursors (50 to 60 kilodaltons) comprising peptide-linked acidic and basic polypeptides. Precursor processing involves the posttranslational cleavage of the peptide bond to yield authentic and polypeptides. This processing has a half-life of 35 to 40 minutes and is preceded by a 45- to 60-minute lag period. Both precursor and subunit polypeptides are shown to exhibit similar molecular weight and pI heterogeneity, and this is suggested to be due to the expression of a multigene family.

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PubMed1984

Plant Desiccation and Protein Synthesis : V. Stability of Poly (A) and Poly (A) RNA during Desiccation and Their Synthesis upon Rehydration in the Desiccation-Tolerant Moss Tortula ruralis and the Intolerant Moss Cratoneuron filicinum.

Upon desiccation of gametophytes of the desiccation-tolerant moss Tortula ruralis preexisting pools of poly(A)(-) RNA (rRNA) remain inact, regardless of the speed at which desiccation is achieved. Preexisting poly(A)(+) RNA pools (mRNA) are unaffected by slow desiccation but are substantially reduced during rapid desiccation. Poly(A)(-) RNA involved in protein synthesis is also unaffected by desiccation, whereas the levels of polysomal poly(A)(+) RNA in rapid- and slow-dried moss closely reflect the state of the protein synthetic complex in these dried samples.Poly(A)(-) RNA pools, both total and polysomal, are also stable during the rehydration of both rapid- and slow-dried moss. The total poly(A)(+) RNA pool decreases upon rehydration, but this reduction is simply an expression of the normal turnover of poly(A)(+) RNA in this moss. Analysis of polysomal fractions during rehydration reveals the continued use of conserved poly(A)(+) RNA for protein synthesis. The rate of synthesis of poly(A)(+) RNA upon rehydration appears to depend upon the speed at which prior desiccation is administered. Rapidly dried moss synthesizes poly(A)(+) RNA at a faster rate, 60 to 120 minutes after the addition of water, than does rehydrated slowly dried moss. Recruitment of this RNA into the protein synthetic complex also follows this pattern. Comparative studies involving the aquatic moss Cratoneuron filicinum are used to gain an insight into the relevance of these findings with respect to the cellular mechanisms associated with desiccation tolerance.

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PubMed1984

Plant Desiccation and Protein Synthesis : VI. Changes in Protein Synthesis Elicited by Desiccation of the Moss Tortula ruralis are Effected at the Translational Level.

Upon rehydration of the moss Tortula ruralis following desiccation at a rapid or slow rate, there is increasing utilization of newly synthesized-poly(A)(+) RNA for protein synthesis. Initially, poly(A)(+) RNA conserved in the dry moss is associated with polysomes, but by 2 hours of rehydration there is an overwhelming recruitment of newly synthesized poly(A)(+) RNA, at the expense of conserved messages. In rehydrated moss, there is a marked synthesis in vivo of new proteins, which are separable by two-dimensional electrophoresis, and identifiable by fluorography. These new proteins, termed rehydration proteins, are synthesized after both rapid and slow desiccation, but their synthesis persists longer after rapid desiccation. The protein patterns obtained following in vitro translation of bulk RNA from hydrated, desiccated, and rehydrated moss were qualitatively identical. Thus the differences in protein patterns observed in vivo must result from preferential selection of specific mRNAs from the same pool, which is indicative of control of protein synthesis at the translational level. The implications of these observations in relation to the response of the moss to drying in its natural environment are discussed.

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PubMed1984

Membrane Organization of the Desiccation-Tolerant Moss Tortula ruralis in Dehydrated States.

Membrane organization of the desiccation tolerant moss Tortula ruralis was studied in several intensely dehydrated states (75% relative humidity [RH], 90% RH, plasmolysis in molar salt, freezing to -20 degrees C) by (31)P nuclear magnetic resonance and ultrastructural analyses. Both methods revealed that even at 75% RH (-400 bars), the moss cellular membranes retained extended phospholipid bilayers. Ultrastructural analyses of the fully hydrated moss showed an extensive proliferation of membrane vesicles in the endoplasmic reticulum. During dehydration, these vesicles form layers of membrane under the plasmalemma and in some cases appear to fuse with the surface membrane. This suggests that these vesicles may serve as a reservoir of membranes to accommodate for membrane surface area changes during desiccation and subsequent rehydration.

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PubMed1984

Induction of heat shock protein messenger RNA in maize mesocotyls by water stress, abscisic Acid, and wounding.

Exposure of the excised growing region of the mesocotyl of young corn seedlings to heat shock stimulated the production of specific heat shock proteins and the intensification of synthesis of two proteins with a molecular weight of approximately 70,000. Water stress and abscisic acid also stimulated synthesis of these 70,000-dalton proteins, and other unique proteins distinct from those induced by heat shock. Growing tissues of intact corn mesocotyls exposed to heat shock, water stress, or abscisic acid accumulated mRNA species homologous to a cloned genomic probe of the 5' end of the 70,000-dalton Drosophila heat shock protein gene. Since cut segments of the mesocotyl under unstressed conditions produced a similar mRNA, we suggest that the hsp 70 gene is activated in corn by a variety of diverse stresses. Production of the mRNA is rapid, but transient, being induced within 3 hours of the imposition of the stress, but declining after reaching a maximum at 9 hours.

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PubMed1983

An analysis of the subunit structure of the crystalloid protein complex from castor bean endosperm.

Chromatographic and electrophoretic studies have shown that the subunits of the crystalloid protein, isolated from mature castor bean (Ricinus communis L. cv Hale) seed endosperm protein bodies, are heterogeneous with molecular weights in the range 49 to 53.5 kilodaltons (kD), and are quantitatively in unequal amounts. Each subunit comprises an alphabeta polypeptide pair which are reduced by 2-mercaptoethanol in two subgroups with molecular weights in the 29 to 34 kD and 20.5 to 23.5 kD ranges. Subunits and corresponding polypeptide pairs are also seen to be heterogeneous in pI following isoelectric focusing. In general, large polypeptides are acidic (pI 4.8-6.2) and small polypeptides basic (pI 7.4-9.4), although overlap of some isoelectric isomers does occur, notably in polypeptides derived from subunits which are quantitatively present in smaller amounts.

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PubMed1982

Stability and Synthesis of Phospholipids during Desiccation and Rehydration of a Desiccation-Tolerant and a Desiccation-Intolerant Moss.

The fatty acid composition of the phospholipids from the desiccation-tolerant moss Tortula ruralis (Hedw.) Gaertn, Meyer and Scherb and the desiccation-intolerant moss Cratoneuron filicinum has been determined. No changes in composition occur in either moss as a consequence of rapid drying, but, after slow drying, there is a decline in some unsaturated fatty acids. Upon rehydration of T. ruralis after slow drying, these acids decline further; however, within 105 minutes, they regain the same levels as those in undesiccated controls. A smaller and more transient decline occurs after rapid desiccation. Most phospholipid unsaturated fatty acids decrease during rehydration of C. filicinum, and their levels are not recovered. After both rapid and slow drying of T. ruralis, acetate and glycerol are incorporated into the phospholipid fraction, although de novo synthesis, alone, might not account for the increase in unsaturated fatty acids upon rehydration. Very little acetate or glycerol is incorporated during rehydration of C. filicinum. Loss of unsaturated fatty acids from the phospholipids of T. ruralis does not appear to be associated with increased lipoxygenase activity. Furthermore, there is little correlation between the extent of peroxidation of fatty acids due to desiccation and changes in the phospholipid fraction.

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PubMed1982

Deposition of Matrix and Crystalloid Storage Proteins during Protein Body Development in the Endosperm of Ricinus communis L. cv. Hale Seeds.

Protein bodies within the endosperm of castor bean (Ricinus communis L. cv. Hale) seeds arise from numerous small vacuoles which progressively become filled with storage protein, of which the crystalloid proteins make up approximately 70%. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) shows that the crystalloids are a family of at least four proteins which reduce to two complementary groups after 2-mercaptoethanol treatment. The matrix, which comprises the remainder, has two major components, the soluble albumins and the lectins. The lectins are the only glycoproteins within the mature protein body. Both cytochemical staining and SDS-PAGE indicate that the synthesis of the crystalloid and the majority of matrix proteins begins some 20 days after pollination. Additionally, the crystalloid proteins are synthesized concurrently, whereas there is temporal variation in the synthesis of matrix proteins.

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PubMed1982

Desiccation of Axes of Phaseolus vulgaris during Development of a Switch from a Development Pattern of Protein Synthesis to a Germination Pattern.

Immature seeds of Phaseolus vulgaris removed from the pod at 32 days of development do not germinate unless first subjected to a desiccation treatment. This change from development to germination caused by premature drying is mirrored in the pattern of protein synthesis by the axes. Rehydrated axes from 32-day-developed seeds cease to synthesize proteins that are uniquely associated with development, but instead synthesize some proteins that are similar to those made in the germinating axes from mature dry seeds. Desiccation of 22-day-developed seeds does not lead to their germination, nor does it cause a switch from a developmental to a germination mode of protein synthesis by the axes. It is proposed that desiccation plays a role in permanently suppressing developmental protein synthesis and in inducing germination protein synthesis.

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PubMed1981

Biogenesis of Mitochondria in Imbibed Peanut Cotyledons : II. DEVELOPMENT OF LIGHT AND HEAVY MITOCHONDRIA.

THERE ARE TWO TYPES OF MITOCHONDRIA PRESENT IN IMBIBED PEANUT COTYLEDONS: a light type (density 1.182 grams per cubic centimeter) and a heavy type (density 1.205 grams per cubic centimeter). The membrane fractions from these two types can be distinguished using sucrose density gradient analysis, and differences in membrane density between the light and heavy types are reflected in differences in their protein N and phospholipid P composition. With increasing time after imbibition, there is a substantial increase in the amount and activity of the light type of mitochondria due to their de novo synthesis. The membrane density of the light mitochondrial fraction declines over 5 days after the start of imbibition as the phospholipid P to protein N ratio increases. The heavy mitochondrial fraction declines during the first 3 days after the start of imbibition, and then it remains at a low, but constant, level thereafter. Even during the decline, however, there is synthesis of proteins comparable to that into light mitochondria. The mitochondrial biogenesis that has been observed in peanut cotyledons is of the light type, the function and physiological importance of the minor heavy type is not known.

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PubMed1981

Protein synthesis and phospholipids in soybean axes in response to imbibitional chilling.

The responses of two cultivars of soybean (Merr.) to a chilling treatment (4 C for first hour of imbibition) were compared. The germination of cv. Biloxi was unaffected by the treatment, while the germination of cv. Fiskeby was reduced. The phospholipid fatty acids of dry axes of the two cultivars were very similar, and, thus, could not be correlated with their responses to chilling. The fatty acid composition of chilling-tolerant Biloxi did not change over a subsequent 23-hour warm incubation, but there was a marked reduction in the unsaturated fatty acids of chilling-sensitive Fiskeby after 12 hours, which may be a symptom of deterioration. Protein synthesis in both cultivars was reduced by the chilling treatment. Redrying of Biloxi axes up to 18 hours after the onset of imbibition had no effect on their germination upon rehydration. Germination of Fiskeby axes was reduced by redrying after 8 hours of imbibition. After 7 months of dry storage of intact seeds, the sensitivity of the axes to chilling was retested. Biloxi axes had become chilling-sensitive, while the germination of Fiskeby axes was reduced to zero by the chilling treatment. A hypothesis is presented that imbibitional chilling sensitivity is an indication of reduced vigor, axes with a high vigor can tolerate the stress, while those without cannot.

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PubMed1980

cis-4-Cyclohexene-1,2-dicarboximide: Inhibitor of phytochrome-promoted seed germination.

cis-4-Cyclohexene-1,2-dicarboximide (CHDC) inhibits the germination of light-requiring seeds in both light and darkness but has no effect upon the germination of non-light-requiring seeds. In lettuce seeds, CHDC inhibits the action of far-red-absorbing form of phytochrome in breaking dormancy. This inhibition can be overcome by benzyladenine and red light together, but not by a combination of red light and gibberellic acid. Gibberellic acid-induced germination of lettuce seeds in darkness is inhibited also by CHDC. Embryos isolated from dark-imbibed lettuce seeds germinate on the inhibitor. CHDC was thought to be an "analogue" of cycloheximide, but it does not inhibit protein synthesis in lettuce seeds. Our results lead us to conclude that CHDC inhibits germination of seeds that require red light to break dormancy and interferes with some aspect of metabolism that is stimulated by far-red-absorbing form of phytochrome.

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PubMed1980

Lipid peroxidation associated with accelerated aging of soybean axes.

Soybean seeds age rapidly during storage at high temperature and high relative humidity. The axes of such aged seeds contain high levels of malondialdehyde, a product of the peroxidation of unsaturated fatty acids. The levels of linoleic (18:2) and linolenic (18:3) acids in a polar lipid (phospholipid) fraction decrease during aging and more dramatically during postaging deterioration. None of these changes occurred in seeds that have been stored at high temperature but low relative humidity. No superoxide dismutase activity was detected in any nonimbibed seed. In viable seeds, activity was detectable 1.5 hours after the onset of imbibition, but none was found in aged seeds up to 5 hours. It is suggested that aging leads to peroxidative changes to lipids and that these could contribute to loss of viability.

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PubMed1980

Development of Mitochondrial Activities in Pea Cotyledons during and following Germination of the Axis.

Development of mitochondrial activities in pea cotyledons during early times after the start of imbibition occurred in two phases. In the first phase (0 to 8 hours after the start of imbibition), succinate or NADH oxidation increased rapidly, while malate or alpha-ketoglutarate oxidation remained low. The latter activities developed only 8 to 12 hours after the start of imbibition (the second phase). Development in the first phase was induced by water uptake, but some development occurred even when the cotyledons were fully imbibed. The presence of the axis was required for the second phase of the development. It is suggested that mitochondrial development in the second phase is brought about by activation of the electron transfer path at a site between the oxidation of endogenous NADH and the reduction of ubiquinone.

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PubMed1980

Development of Mitochondrial Activities in Pea Cotyledons: INFLUENCE OF DESICCATION DURING AND FOLLOWING GERMINATION OF THE AXIS.

Mitochondria in 4-hour imbibed and desiccated pea cotyledons develop in a similar manner upon rehydration to those in cotyledons hydrated only once. As a consequence of desiccation during imbibition, mitochondria revert to their original state as in the mature dry cotyledon, although limited damage occurs. This damage is more evident when the initial imbibition time before desiccation is longer. The presence of the axis does not protect cotyledonary mitochondria from damage, nor does it influence mitochondrial development upon rehydration of desiccated cotyledons. During the early hours after the start of imbibition mitochondrial development is dependent both upon hydration levels of the cotyledon and upon other metabolic processes, as shown by sensitivity to conditions that prevent ATP synthesis.

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PubMed1979

Respiration in Relation to Adenosine Triphosphate Content during Desiccation and Rehydration of a Desiccation-tolerant and a Desiccation-intolerant Moss.

O(2) consumption by the desiccation-tolerant moss Tortula ruralis and the desiccation-intolerant Cratoneuron filicinum increased markedly during the latter stages of desiccation. ATP content of the mosses during desiccation was not correlated with O(2) consumption, but was influenced by the rate at which the mosses lost water. The more rapid the water loss, the more ATP that was present in the dry mosses. The pattern of O(2) consumption on rehydration also was influenced by the previous rate of desiccation. After rapid desiccation of T. ruralis O(2) consumption upon rehydration was considerably elevated, and for up to 24 hours. After very slow desiccation the elevation was small and brief. Normal O(2) consumption did not occur in C. filicinum after rapid desiccation, but did so within a few hours of rehydration after slower speeds of drying. ATP levels in T. ruralis returned to normal within 5 to 10 minutes of rehydration. In C. filicinum, increases in ATP were closely correlated with O(2) consumption. These observations are considered to be related to differential damage caused to mitochondria and to cellular integrity by different speeds of water loss. The desiccation-tolerant moss appears to be able to repair the severe damage imposed by rapid desiccation whereas the desiccation-intolerant moss cannot.

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