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.     

Control of ribulose 1,5-bisphosphate carboxylase synthesis in the cotyledons of Citrullus lanatus

White light completely inhibits the germination of Citrullus lanatus (Thunb.) Matsumara & Nakai seeds. Under these conditions light does not induce ribulose bisphosphate carboxylase (Rubisco) synthesis in the cotyledons. Although the seeds apparently are capable of attaining sufficient levels of the far-red light absorbing form of phytochrome, Pfr, in the dark to permit germination this does not induce Rubisco synthesis. However, it appears that a substantial amount of synthesis of the small subunit (SSU) takes place in the dark. The synthesis of the two subunits is therefore not tightly coordinated in this tissue, and in none of the treatments were equimolar concentrations of the two subunits present in the cotyledons. However, if the seeds are allowed to start germination in the dark and are then transferred to continuous light, Rubisco synthesis is induced. This induction of Rubisco synthesis in the cotyledons is dependent on the presence of the elongating radicle. Kinetin induces synthesis of Rubisco in isolated cotyledons in both the light and the dark, while 2-chloroethanephosphonic acid (Ethrel) only restores the sensitivity towards light activation of Rubisco synthesis. Synthesis of Rubisco in isolated cotyledons in the presence of these two compounds differs from that of the intact tissue in that the synthesis of the SSU is stimulated more than the synthesis of the large subunit (LSU).     

Early protein synthesis during germination of barley embryos and its relationship to RNA synthesis

In barley embryo, protein synthesis as judged from the incorporationof labelled precursors, starts at about 15 min after the commencementof germination. Evidence suggests that these early proteinsare essential for germination and are programmed by a conservedpolyadenylate-containing mRNA, preserved in dry embryos. Althoughlow DNA-dependent RNA polymerase activity is present in drybarley embryos, RNA synthesis does not commence immediatelyafter water imbibition. It is initiated only after 2 hr of germinationand its synthesis requires the presence of early proteins. Furthermore,the activity of RNA polymerase increases with an increase ingermination time and after 40 hr of germination, the activityof RNA polymerase is about fivefold higher than that in dryembryo. However, cydoheximide completely blocks the enhancedactivity of RNA polymerase, suggesting a role of early proteinsin the initiation of new RNA synthesis in this developmentalsystem. (Received October 26, 1979; )     

The role of darkness, GA and fusicoccin (FC) in breaking photodormancy in Phacelia tanacetifolia seeds

The germination of the negatively photoblastic seeds of Phacelia tanacetifolia Benth. (cv. Bleu Clair) is promoted by gibberellic acid and fusicoccin. In the dark, or in the light in the presence of fusicoccin, seed germination is accompanied by an increase of gibberellic acid-like substances. In these conditions, the inhibition of the synthesis of gibberellic acid-like substances does not prevent seed germination, but it affects the growth and the survival of the seedlings. Seed germination, growth, and survival of seedlings are discussed in relation to phytochrome, fusicoccin, and gibberellic acid-iite substances.     

Pollen protein synthesis and control of incompatibility in Brassica

Summary Excised but otherwise intact cabbage (Brassica oleracea var. capitata) stigmas release a watersoluble substance which selectively inhibits germination of self-but not cross-pollen. The inhibitory effect on self-pollen germination is dependent on both the concentration of stigma extract and on the time of addition. Low concentrations of stigma extract inhibit when present from the start (zero time additions) of pollen imbibition, whereas high concentrations do not. High concentrations inhibit when stigma extracts are added 1 to 2 minutes after the start of pollen imbibition, but germination is increasingly less inhibited when additions are delayed 2 to 4 minutes. Similar inhibition kinetics are also observed with delayed additions of cordycepin and cycloheximide. Stigma extracts selectively inhibit leucine-¹⁴C incorporation into proteins of self-pollen. We conclude that germination does not require protein synthesis whereas the regulation of self-incompatibility does.Department of Vegetable Crops Publication No. VC 718.     

Long-lived Messenger RNA and its Relationship to Protein Synthesis During Germination of Pea (Pisum sativum L.) Seeds

Synthesis of both protein and RNA is initiated very early ingermination in the embryo axes of pea seeds. The early RNA synthesisinvolves all three types, although there is some evidence forpreferential synthesis of mRNA in the first few hours afterthe onset of imbibition. In addition to newly synthesized mRNA,the embryo axis also contains long-lived mRNA. The amount ofthis long-lived mRNA declines markedly during the first 20 hof germination. Synthesis of both protein and RNA is initiated very early ingermination in the embryo axes of pea seeds. The early RNA synthesisinvolves all three types, although there is some evidence forpreferential synthesis of mRNA in the first few hours afterthe onset of imbibition. In addition to newly synthesized mRNA,the embryo axis also contains long-lived mRNA. The amount ofthis long-lived mRNA declines markedly during the first 20 hof germination. Results from in vitro and in vivo protein synthesis experimentsand from studies of polysome formation suggest that much ofthe long-lived mRNA present in the embryo axis does not directprotein synthesis. The increase in the rate of protein synthesisduring germination is thus dependent on recruitment of newlysynthesized mRNA molecules. Pea, Pisum sativum L., germination, mRNA, protein synthesis     

Reactive products formed by peroxidase catalyzed oxidation of p-phenetidine

The drug 4-nitroquinoline 1-oxide (4NQO) is a potent inhibitor of Dictyostelium discoideum spore germination. This inexpensive, water soluble drug is active at a concentration of 5 micrograms/ml (26 microM) and permeates the spore at all stages in germination. Spores subjected to 4NQO treatment exhibit an irreversible blockage of myxamoebae emergence, but spore activation, post-activation lag, and swelling are not affected. Swollen 4NQO-treated spores lose the outer two spore walls but lack the ability to degrade the innermost wall. The drug does not affect oxygen uptake during post-activation lag or swelling, and only a stage specific depression in O2 uptake is observed when control spores begin to release myxamoebae. When added early in germination, 4NQO blocks the incorporation of [3H] uracil into a cold trichloroacetic acid (TCA) insoluble fraction by 98%. However, when the drug is added midway through germination and followed by a pulse labelling period of 1 h, only 65% inhibition of RNA synthesis is observed. This lack of complete inhibition may occur because the drug requires metabolic activation; thus, new rounds of RNA synthesis may have initiated before the drug became fully activated. 4NQO also blocks the de novo expression of beta-glucosidase activity when added early in germination. Additionally, we observe that vegetative cellular slime mold cells are 100 times more resistant than spores to 4NQO-induced damage. Taken together, our results support the observation that RNA synthesis is only required for the emergence stage of germination and that dormant D. discoideum spores may lack efficient excision repair mechanisms.     

Cellular events in growth and germination of giant conidia of Neurospora crassa

During growth of conidia in 3.22 M ethylene glycol the increase in the number of the nuclei is proportional to the increase in volume only in the phase of maximum growth rate and is lower in the preceding and in the following periods of growth. DNA synthesis similarly initiates later and decreases faster than protein synthesis. The dilution of ethylene glycol is followed by the germination of giant conidia, which is characterized by the absence of a lag phase, a high degree of synchrony and the formation of more than one germ tube per conidium. The number of germ tubes is dependent on the volume reached by conidia at the end of the treatment and does not increase with time. The resuming of DNA synthesis after germination is preceded by a sharp increase in protein synthesis and the division of almost half of the nuclei and shows a synchronized pattern. Results are discussed in the light of models of growth proposed for eukaryotic cells.     

Release of dormancy during after-ripening of Agrostemma githago seeds

Freshly harvested seeds of Agrostemma githago L. do not germinate when they are imbibed at 20°C. The block is located in the embryo and is relased by dry storage at 20°C (after-ripening). Freshly harvested seeds complete only a small part of the processes that occur in after-ripened seeds during the lag phase prior to germination (radicle protrusion). After-ripening removed the block on lag phase processes much faster than the block on germination. This was shown both by direct determinations of the completion of lag phase processes and by measurements of the rate of axial protein synthesis, which approximately doubles when seeds are progressing through the lag phase. It is concluded that the percentage germination does not adequately reflect the extent to which the dormancy mechanism has been overcome.     

RNA synthesis and the germination of light-sensitive lettuce seeds

Summary The germination of lettuce seeds is inhibited by the nucleotide base analogue 6-methylpurine. RNA synthesis has been measured during imbibition and germination as ³²P-phosphate incorporation into RNA species as fractionated by polyacrylamide gel electrophoresis. Seeds were surface sterilized and imbibed in the presence of various antibiotics. RNA preparations from lettuce seeds were coelectrophoresed with ³H-RNA prepared from bacteria to check for bacterial contamination of the seeds. There is a much higher rate of RNA synthesis in illuminated, germinating seeds as compared to dark, non-germinating seeds. This difference does not develop until after 12 hours of imbibition at 27°, which is the time of onset of germination and radicle growth.This investigation was supported by a contract from the United States Department of Agriculture (No. 616-15-3). Journal paper of the Purdue Agriculture Experiment Station.     

Regulation der Nucleinsäuren-Synthese durch Polyamine in keimendem Pollen vonPetunia

Summary Putrescine, spermine, spermidine, and agmatine in concentrations between 5–15 g/ml inhibit pollen germination. Whereas spermine reduces pollen tube length, putrecine and agmatine do not affect pollen tube growth. Spermidine effects a small increase (about 5%) of pollen tube elongation. Spermine and spermidine can be found in pollen. Addition of spermine (7 or 10 g/ml) depresses protein synthesis, whilst spermidine does not affect protein synthesis. On the basis of uridine-5-T incorporation it could be shown that both spermine and spermidine increase RNA synthesis. On tho basis of thymidine-T incorporation in the first hpurs of germination it seems that DNA synthesis is also stimulated by spermine and spermidine present in the medium. A net increase of nucleic acids was found when spermidine was added to the germination substrate.These results are interpreted as suggesting that, in the pollen tubes investigated, polyamine concentration may be a factor in the regulation of nucleic acid synthesis, resulting in a prolonged synthesis of specific proteins and in this way influencing growth and the developmental pattern of pollen tubes.     

The development of ribonuclease and acid phosphatase during germination of Pisum arvense

1. Development of ribonuclease activity in the cotyledons of germinating peas is biphasic, the time of appearance of the two phases depending on the conditions of growth. 2. Acid phosphatase exhibits a single phase of development. 3. Cycloheximide inhibits development of ribonuclease activity in phase II but not in phase I. 4. (14)C-labelled amino acids are not incorporated into ribonuclease isolated during phase I. 5. The buoyant density of ribonuclease isolated during phase I is not affected by imbibition of the seed in 80% deuterium oxide. 6. Acid phosphatase was isolated from the supernatant fraction of the cotyledons of germinating peas and partially purified. 7. Development of acid phosphatase activity during germination is inhibited by treatment of the seed with cycloheximide or actinomycin D. 8. Partial purification of acid phosphatase from peas germinated in the presence of (14)C-labelled amino acids suggests that the enzyme is radioactively labelled. 9. Germination of peas in the presence of 80% deuterium oxide results in an increase in the buoyant density of acid phosphatase. 10. The results suggest that increase in ribonuclease activity during the first 4 days of germination does not result from synthesis of protein de novo, but that the corresponding increase in acid phosphatase activity does result from synthesis de novo.     

Lipid turnover during morphogenesis in the water mold Blastocladiella emersonii

The lipid content of $\text{Blastocladiella emersonii}$ zoospores is 5 pg/cell or about 13% of dry weight. Within the first few minutes of germination 60–70% of total zoospore lipid is lost, with neutral lipid, glycolipid and phospholipid fractions decreasing to about the same extent. These changes in lipid content precede the breakdown during germination of the complex and extensive membrane system of zoospores. During growth, which immediately follows germination, net phospholipid synthesis resumes so that total lipid is maintained at 6% of dry weight, but net synthesis of neutral and glycolipid does not begin until induction of sporulation. During sporulation the phospholipid level decreases so that the distribution of lipid among the three fractions approaches that found in zoospores. These changes in lipid content suggest that zoospore membranes containing neutral and glycolipids are synthesized $\text{de novo}$ during spore formation.     

Ethylene production is associated with germination but not seed dormancy in red rice

BACKGROUND AND AIMS: The relationship between ethylene production and both seed dormancy and germination was investigated using red rice (weedy rice) as a model species. METHODS: Both fully dormant and after-ripened (non-dormant) naked caryopses were incubated with or without inhibitors of ethylene synthesis [aminoethoxyvinylglycine (AVG)] and perception [silver thiosulfate (STS)], or in the presence of the natural ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC). The kinetics of ethylene emissions were measured with a sensitive laser-photoacoustic system. KEY RESULTS: Dormant red rice caryopses did not produce ethylene. In non-dormant caryopses, ethylene evolution never preceded the first visible stage of germination (pericarp splitting), and ethylene inhibitors completely blocked ethylene production, but not pericarp splitting. Accordingly, endogenous ACC appeared to be lacking before pericarp splitting. However, early seedling growth (radicle or coleoptile attaining the length of 1 mm) followed ethylene evolution and was delayed by the inhibitors. Wounding the dormant caryopses induced them to germinate and produce ethylene, but their germination was slow and pericarp splitting could be speeded up by ethylene. CONCLUSIONS: The findings suggest that, in red rice, endogenous ethylene stimulates the growth of the nascent seedling, but does not affect seed dormancy or germination inception. Correspondingly, this phytohormone does not play a role in the dormancy breakage induced by wounding, but accelerates germination after such breakage has occurred.     

Modulation of deoxyribonucleic acid polymerase III level during the life cycle of Bacillus subtilis.

Deoxyribonucleic acid (DNA) polymerase III is not detectable in Bacillus subtilis spores; the enzyme activity appears 20 to 30 min after spore activation and rapidly increases just before the onset of the first round of DNA replication (30 min later); the level of polymerase III further increases and reaches its maximum (on a per-genome basis) when the cells enter the vegetative phase of growth; this level is six- to eightfold higher than the one observed during germination. In the stationary phase, the polymerase III drops to levels comparable to those found in germinating spores at the first round of replication. On the contrary, DNA polymerase I is present at appreciable levels in the dormant spore; it increases during vegetative growth by a factor of three and, during the stationary phase, reaches its maximum level which is sixfold higher than that observed in the spores. The block of protein synthesis during vegetative growth does not cause an appreciable reduction of the two enzymes (in absolute terms), showing that the regulation of their levels is probably not due to a balance between synthesis and breakdown. These results indicate that polymerase III is probably one of the factors controlling the initiation of DNA synthesis during spore germination.     

Cell cycle analysis in asynchronous cultures using the BUdR-Hoechst technique.

During synchronized germination of spores of Dictyostelium discoideum, protein synthesis begins almost concomitantly with syntheses of messenger-like RNA (mlRNA) and 4–5S RNA (presumably tRNA) in the swollen spore stage and the initiation of ribosomal RNA (rRNA) synthesis is somewhat delayed. DNA synthesis occurs in the early stages of the amoeba emergence phase. Cycloheximide (200 μg/ml) blocked spore germination as well as total protein synthesis, whereas actinomycin D (60 μg/ml) did not affect either. This concentration of actinomycin D selectively inhibited formation of rRNA but did not influence the synthesis of mlRNA. Examinations of RNA labeled with [¹⁴C]uracil during germination indicated that polysomes initially detectable in the course of the germination process contain ¹⁴C-labeled mlRNA. It was concluded that at least some of mRNA synthesized during germination of D. discoideum spores is involved in protein synthesis required for the germination.