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PubMed2004

The effect of alpha-amanitin on the Arabidopsis seed proteome highlights the distinct roles of stored and neosynthesized mRNAs during germination.

To investigate the role of stored and neosynthesized mRNAs in seed germination, we examined the effect of alpha-amanitin, a transcriptional inhibitor targeting RNA polymerase II, on the germination of nondormant Arabidopsis seeds. We used transparent testa mutants, of which seed coat is highly permeable, to better ascertain that the drug can reach the embryo during seed imbibition. Even with the most permeable mutant (tt2-1), germination (radicle protrusion) occurred in the absence of transcription, while subsequent seedling growth was blocked. In contrast, germination was abolished in the presence of the translational inhibitor cycloheximide. Taken together, the results highlight the role of stored proteins and mRNAs for germination in Arabidopsis and show that in this species the potential for germination is largely programmed during the seed maturation process. The alpha-amanitin-resistant germination exhibited characteristic features. First, this germination was strongly slowed down, indicating that de novo transcription normally allows the synthesis of factor(s) activating the germination rate. Second, the sensitivity of germination to gibberellic acid was reduced 15-fold, confirming the role of this phytohormone in germination. Third, de novo synthesis of enzymes involved in reserve mobilization and resumption of metabolic activity was repressed, thus accounting for the failure in seedling establishment. Fourth, germinating seeds can recapitulate at least part of the seed maturation program, being capable of using mRNAs stored during development. Thus, commitment to germination and plant growth requires transcription of genes allowing the imbibed seed to discriminate between mRNAs to be utilized in germination and those to be destroyed.

Amanitins↗
PubMed1979

Genetics analysis of spore germination mutants of Bacillus subtilis 168: the correlation of phenotype with map location.

The isolation and characterization of 29 new germination (Ger) mutants of Bacillus subtilis 168 is described. These were classified, along with previously described mutants, into seven groups according to map location. The mutations in 26 GerA mutants mapped between cysB and thr; detailed mapping of two of these has located them very close to citG. These mutants were deficient in germination in alanine, but responded to the germinative combination of asparagine, glucose, fructose and KCl. One GerB mutant mapped on the origin-proximal side of hisA; it was normal in germination in alanine, but deficient in termination in a mixture of asparagine, glucose, fructose and KCl. Two GerC mutants were linked to lys, but were separable from a temperature-sensitive growth deficiency mapping between lys and trp. The GerC mutants had a similar germination phenotype to the GerA mutants. Three GerD mutants did not germinate in either of the above germinants or in Penassay Broth. They were located on the side of ery distal to cysA. The GerE mutant, which did not germinate in any of the three germinants, was located very close to citF and possessed an altered spore coat. The two GerF mutants were defective in germination in all three germinants and mapped on the origin proximal-side of hisA, but much closer to his than did the GerB mutant. A phosphoglycerate kinase-negative mutant altered in germination mapped between cysB and hisA (GerG). These mutants have established a minimum of seven locations important to germination, and will be useful in the development and appraisal of theories of spore germination.

Bacillus subtilis↗
PubMed1994

The Induction of Seed Germination in Arabidopsis thaliana Is Regulated Principally by Phytochrome B and Secondarily by Phytochrome A.

We examined whether spectrally active phytochrome A (PhyA) and phytochrome B (PhyB) play specific roles in the induction of seed germination in Arabidopsis thaliana (L.) Heynh., using PhyA- and PhyB-null mutants, fre1-1 (A. Nagatani, J.W. Reed, J. Chory [1993] Plant Physiol 102: 269-277) and hy3-Bo64 (J. Reed, P.Nagpal, D.S. Poole, M. Furuya, J. Chory [1993] Plant Cell 5: 147-157). When dormant seeds of each genotype imbibed in the dark on aqueous agar plates, the hy3 (phyB) mutant did not germinate, whereas the fre1 (phyA) mutant germinated at a rate of 50 to 60%, and the wild type (WT) germinated at a rate of 60 to 70%. By contrast, seeds of all genotypes germinated to nearly 100% when plated in continuous irradiation with white or red light. When plated in continuous far-red light, however, frequencies of seed germination of the WT and the fre1 and hy3 mutants averaged 14, nearly 0, and 47%, respectively, suggesting that PhyB in the red-absorbing form prevents PhyA-dependent germination under continuous far-red light. When irradiated briefly with red or far-red light after imbibition for 1 h, a typical photoreversible effect on seed germination was observed in the fre1 mutant and the WT but not in the hy3 mutant. In contrast, when allowed to imbibe in the dark for 24 to 48 h and exposed to red light, the seed germination frequencies of the hy3 mutant were more than 40%. Immunoblot analyses of the mutant seeds showed that PhyB apoprotein accumulated in dormant seeds of the WT and the fre1 mutant as much as in the seeds that had imbibed. In contrast, PhyA apoprotein, although detected in etiolated seedlings grown in the dark for 5 d, was not detectable in the dormant seeds of the WT and the hy3 mutant. The above physiological and immunochemical evidence indicates that PhyB in the far-red-absorbing form was stored in the Arabidopsis seeds and resulted in germination in the dark. Hence, PhyA does not play any role in dark germination but induces germination under continuous irradiation with far-red light. Finally, we examined seeds from a signal transduction mutant, det1, and a det1/hy3 double mutant. The det1 seeds exhibited photoreversible responses of germination on aqueous agar plates, and the det1/hy3 double mutant seeds did not. Hence, DET1 is likely to act in a distinct pathway from PhyB in the photoregulation of seed germination.

Journal Article↗
PubMed2006

Characterization of germination receptors of Bacillus cereus ATCC 14579.

Specific amino acids, purine ribonucleosides, or a combination of the two is required for efficient germination of endospores of Bacillus cereus ATCC 14579. A survey including 20 different amino acids showed that l-alanine, l-cysteine, l-threonine, and l-glutamine are capable of initiating the germination of endospores of B. cereus ATCC 14579. In addition, the purine ribonucleosides inosine and adenosine can trigger germination of the spores. Advanced annotation of the B. cereus ATCC 14579 genome revealed the presence of seven putative germination (ger) operons, termed gerG, gerI, gerK, gerL, gerQ, gerR, and gerS. To determine the role of the encoded putative receptors in nutrient-induced germination, disruption mutants were constructed by the insertion of pMUTIN4 into each of the seven operons. Four of the seven mutants were affected in the germination response to amino acids or purine ribonucleosides, whereas no phenotype could be attributed to the mutants with disrupted gerK, gerL, and gerS loci. The strain with a disrupted gerR operon was severely hampered in the ability to germinate: germination occurred in response to l-glutamine but not in the presence of any of the other amino acids tested. The gerG mutant showed significantly reduced l-glutamine-induced germination, which points to a role of this receptor in the l-glutamine germination signaling pathway. gerR, gerI, and gerQ mutants showed reduced germination rates in the presence of inosine, suggesting a role for these operons in ribonucleoside signaling. Efficient germination by the combination of l-glutamine and inosine was shown to involve the gerG and gerI operons, since the germination of mutants lacking either one of these receptors was significantly reduced. Germination triggered by the combination of l-phenylalanine and inosine was lost in the gerI mutant, indicating that both molecules are effective at the GerI receptor.

Adenosine↗
PubMed1998

Role of the gerI operon of Bacillus cereus 569 in the response of spores to germinants.

Bacillus cereus 569 (ATCC 10876) germinates in response to inosine or to L-alanine, but the most rapid germination response is elicited by a combination of these germinants. Mutants defective in their germination response to either inosine or to L-alanine were isolated after Tn917-LTV1 mutagenesis and enrichment procedures; one class of mutant could not germinate in response to inosine as a sole germinant but still germinated in response to L-alanine, although at a reduced rate; another mutant germinated normally in response to inosine but was slowed in its germination response to L-alanine. These mutants demonstrated that at least two signal response pathways are involved in the triggering of germination. Stimulation of germination in L-alanine by limiting concentrations of inosine and stimulation of germination in inosine by low concentrations of L-alanine were still detectable in these mutants, suggesting that such stimulation is not dependent on complete functionality of both these germination loci. Two transposon insertions that affected inosine germination were found to be located 2.2 kb apart on the chromosome. This region was cloned and sequenced, revealing an operon of three open reading frames homologous to those in the gerA and related operons of Bacillus subtilis. The individual genes of this gerI operon have been named gerIA, gerIB, and gerIC. The GerIA protein is predicted to possess an unusually long, charged, N-terminal domain containing nine tandem copies of a 13-amino-acid glutamine- and serine-rich sequence.

Adenosine↗
PubMed2003

Stimulation of gamma-aminobutyric acid synthesis activity in brown rice by a chitosan/glutamic acid germination solution and calcium/calmodulin.

Changes in the concentrations of gamma-aminobutyric acid (GABA), soluble calcium ions, glutamic acid, and the activity of glutamate decarboxylase (GAD) were investigated in non-germinated vs. germinated brown rice. Brown rice was germinated for 72 h by applying each of the following solutions: (1) distilled water, (2) 5 mM lactic acid, (3) 50 ppm chitosan in 5 mM lactic acid, (4) 5 mM glutamic acid, and (5) 50 ppm chitosan in 5 mM glutamic acid. GABA concentrations were enhanced in all of the germinated brown rice when compared to the non-germinated brown rice. The GABA concentration was highest in the chitosan/glutamic acid that germinated brown rice at 2,011 nmol/g fresh weight, which was 13 times higher than the GABA concentration in the non-germinated brown rice at 154 nmol/g fresh weight. The concentrations of glutamic acid were significantly decreased in all of the germinated rice, regardless of the germination solution. Soluble calcium and GAD were higher in the germinated brown rice with the chitosan/glutamic acid solution when compared to the rice that was germinated in the other solutions. GAD that was partially purified from germinated brown rice was stimulated about 3.6-fold by the addition of calmodulin in the presence of calcium. These data show that the germination of brown rice in a chitosan/glutamic acid solution can significantly increase GABA synthesis activity and the concentration of GABA.

Calcium↗
PubMed1992

In vitro enzymatic hydrolysis of protein and protein pattern change of soya and faba beans during germination.

In addition to technological processes like heat treatment, germination can be an alternative process for the improvement of protein quality of legumes. This was demonstrated by enzymatic protein hydrolysis of flour of germinated faba and soya beans, using a pepsin-pancreatin enzyme system. SDS-PAGE was used to study the changes in protein pattern of these legumes during germination. In addition, the effect of germination on the content of condensed tannins in flour from germinated faba beans and trypsin inhibitors in flour from germinated soya beans were studied. Germination for five days resulted in a maximum increase in enzymatic protein hydrolysis by 21.3% in flour from faba beans and by 25.7% in flour from soya beans after 12 hours of germination. Protein patterns, obtained with SDS-PAGE demonstrated a considerable protein breakdown during germination between day 2 and 3 in faba beans and between day 1 and 2 in soya beans. The tannin content in flour from faba beans decreased by 29.7% after seven days of germination, but the tannin content of the hulls of the faba beans did not change during that period of germination. The trypsin inhibitors in flour from soya beans decreased by 25.5% after seven days of germination. We conclude that the increased enzymatic hydrolysis of protein in both legumes cannot be explained by a decrease of tannins or trypsin inhibitors. The possible explanation is that through degradation of proteins during germination of the legumes, the cleaved protein fragments are more susceptible for hydrolysis by pepsin-pancreatin.

Adsorption↗
PubMed1997

The germinability of spores of a psychrotolerant, non-proteolytic strain of Clostridium botulinum is influenced by their formation and storage temperature.

The formation and storage temperatures of Clostridium botulinum spores are shown to influence their subsequent ability to germinate. Spores were formed at 10 degrees, 20 degrees, 30 degrees and 37 degrees C and following harvest were stored as aqueous suspensions at 20 degrees C (ambient temperature), 4 degrees C (refrigerated) or -20 degrees C (frozen) for periods of up to 1 month. The spores formed at 20 degrees C germinated most rapidly and to the greatest extent. When the spores were germinated immediately after harvest (fresh), there was no difference in the germinability of those spores formed at 20 degrees or 30 degrees C, whether or not they had been heat-shocked before use. However, following storage overnight or longer, differences in the relative germinabilities of the different spore samples were seen. Spores which had been stored at ambient temperature overnight germinated significantly faster and to a greater extent than did those which had been stored for up to 1 month. Similar differences were also observed between spores germinated fresh and those stored overnight, when the spores were stored refrigerated or frozen. Germinability was also influenced by the temperature of storage, since there were differences between spores formed at the same temperature but stored at different temperatures for the same period of time: for example, when spores which had been formed at 20 degrees C were germinated at 10 degrees C following a heat-shock, those which had been stored at ambient temperature germinated faster and to a greater extent than did those which had been stored refrigerated or frozen. It is concluded that there is a complex interaction between formation, storage and germination temperatures, which determines spore germinability. The fact that the changes are time-dependent and can occur in the frozen state is taken to mean that they are physico-chemical rather than metabolic. It is also significant in relation to refrigerated foods which are at risk from Cl. botulinum in that changes which occur during cool or frozen storage can enhance the germinability of spores if the temperature rises above that of chill cabinets.

Clostridium botulinum↗
PubMed1982

Effect of temperature on spore germination and vegetative cell growth of Clostridium botulinum.

Spore germination and vegetative growth of Clostridium botulinum type E strain VH at 2 to 50 degrees C were studied. At all of these temperatures, germination began immediately after the addition of the spores to the germination medium. Microscopic observations during germination revealed three types of spores: phase bright (ungerminated), phase variable (partially germinated), and phase dark (fully germinated). At all temperatures except 50 degrees C, there was a pronounced lag between the initial appearance of phase-variable spores and their eventual conversion to phase-dark spores. The number of partially germinated spores increased steadily, reaching 40 to 60% by 18 to 21 h of incubation. During this time, phase-dark, fully germinated spores developed slowly and did not exceed 28% in any of the samples. At 18 to 26 h of incubation, the rate of full germination increased abruptly four-fold. There was extensive and relatively rapid germination at 2 degrees C, the lowest temperature tested, yielding about 60% phase-variable spores by 18 h, which became phase-dark by 26 h of incubation. The optimum temperature for partial and full germination was consistently 9 degrees C. Germination at 50 degrees C was exceptionally rapid and was completed within 1 to 2 h, although 40% remained phase bright. Vegetative cells showed detectable growth at 6 to 41 degrees C, with a distinct optimum at 32.5 degrees C. No growth occurred at 50 degrees C, and only marginal growth was observed at 6 to 14 degrees C. The psychrophilic nature of the germination process coupled with the cold tolerance of vegetative growth appears to give C. botulinum type E an advantage in cold climates as well as in cold-stored foods.

Clostridium botulinum↗
PubMed1985

Inhibition of germinant binding by bacterial spores in acidic environments.

Commitment to germinate occurred in both Clostridium botulinum and Bacillus cereus spores during 0.5 min of exposure to 100 mM L-alanine or L-cysteine, measured by the inability of germination inhibitors (D form of amino acid) to inhibit germination. Spore germination at pH 4.5 was inhibited because the germinant did not bind to the trigger sites. C. botulinum spores exposed to 100 mM L-alanine or L-cysteine at pH 4.5 remained sensitive to D-amino acid inhibition at pH 7, indicating that no germinants had bound to the trigger site at pH 4.5. Inhibition of germinant binding at pH 4.5 was reversible but lagged in commitment to germinate upon transfer to pH 7. Spores sequentially exposed to pH 4.5 buffer and pH 7 buffer with the germinant also demonstrated a lag in commitment to germinate. The pH at which binding was inhibited was not significantly affected by composition of the buffer or by reduced germinant concentrations (10 mM). Nonspecific uptake of L-[3H]alanine by C. botulinum spores was not inhibited at pH 4.5. Inhibition of germinant binding in acidic environments appeared to be due to protonation of a functional group in or near the trigger site. This may represent a general mechanism for inhibition of spore germination in acidic environments.

Alanine↗
PubMed1978

Characterization of germination and activation of Bdellovibrio bdellocysts.

A simple method of assaying germination of bdellocysts in liquid medium has been devised. Bdellocysts can be induced to germinate by any of eight L-amino acids or the monovalent cations K+ and NH4+. L-Glutamine was the best individual inducer of germination, although the resulting rate of germination was much slower than in a complex medium. The use of a defined germination medium containing L-glutamine, KCl, and NH4Cl produced a faster rate of germination than did complex media. Bdellocysts germinated most rapidly at pH 8.0 and at 35 degrees C and required aerobic conditions. Respiration of bdellocysts began to increase at 3 min after the addition of germinants. Germination was inhibited by respiratory-chain inhibitors and by inhibitors of macromolecular synthesis. When bdellocysts were heat shocked at sublethal temperatures for short periods, there was no effect on the rate of germination in the defined germination medium or in the complex medium. However, heat-shocked bdellocysts germinated at a much faster rate in the presence of single inducers of germination when compared to nonshocked bdellocytes.

Amino Acids↗
PubMed1964

EFFECT OF SUGARS AND OTHER CARBON COMPOUNDS ON GERMINATION AND POSTGERMINATIVE DEVELOPMENT OF BACILLUS MEGATERIUM SPORES.

Hyatt, Mildred T. (Pioneering Research Division. U.S. Army Natick Laboratories, Natick, Mass.), and Hillel S. Levinson. Effect of sugars and other carbon compounds on germination and postgerminative development of Bacillus megaterium spores. J. Bacteriol. 88:1403-1415. 1964.-A total of 77 carbon-containing compounds were tested for their ability to support germination and postgerminative development of Bacillus megaterium spores. The only effective germination agents were certain of the hexose sugars and their derivatives. With unheated spores, only d-glucose, d-mannose, 2-deoxy-d-glucose, d-glucosamine, and N-acetyl-d-glucosamine (all at 25 mm) supported appreciable germination (ca. 25%). Heat-shock at 60 C for 10 min increased germination and decreased the concentration of sugar required for germination, so that these compounds, at 2.5 mm, supported 40 to 60% germination. Higher concentrations (25 mm) of other compounds, d-fructose, l-sorbose, d-allose, d-altrose, 2-hydroxyethyl-d-glucose, and beta-methyl-d-glucoside, were required for appreciable germination of heated spores. Glucose or mannose contamination accounted for the germination apparently induced by certain other sugars. Ionic contamination did not appear to contribute to the germination induced by d-glucose, d-fructose, 2-deoxy-d-glucose, or l-sorbose. There was no clear-cut evidence for a multiplicity of metabolic pathways in the triggering of B. megaterium spore germination by various sugars. Postgerminative development of germinated spores was supported by a wider variety of carbon compounds, including some pentoses and hexoses, many oligosaccharides, sugar derivatives, some alcohols, and some of the tricarboxylic acid cycle intermediates. Compounds effective for germination were not necessarily utilizable for growth, and vice versa. Oxygen consumption rates reflected the progress and extent of postgerminative development on the various carbon compounds. Utilization of glucose during postgerminative development was followed, and the concentration requirements were determined.

Acetylglucosamine↗
PubMed1981

Changes in the chemical composition of oospores of Pythium aphanidermatum during bimodal germination.

The developmental mode by which oospores of Pythium aphanidermatum germinate may be controlled by the concentration of glucose present in the germination medium. When incubated in a liquid medium containing emulsified lecithin without added glucose (S + L), oospores germinated indirectly, with zoospore release occurring during the 10th to 13th h. A decrease in dry weight of the fungus took place by the 13th h of indirect germination. When 0.2 mM glucose was added to S + L, the dry weight of germlings increased and direct germination occurred without zoospore formation. Polar lipid comprised the bulk of total acylglycerides of dormant oospores. A greater decrease in total fatty acid content took place during direct germination than during indirect germination. During both developmental modes of germination, polar lipid content decreased considerably; neutral lipids, however, increased during indirect germination and decreased during direct germination. Protein content of the fungus increased in both developmental modes of germination, being initially 9.7% of the dry weight of dormant oospores. After 13 h of incubation, KOH-soluble polysaccharide decreased by 35% during direct germination and by 48% during indirect germination.

Fatty Acids↗
PubMed1993

Germin, a protein marker of early plant development, is an oxalate oxidase.

Germin is a homopentameric glycoprotein, the synthesis of which coincides with the onset of growth in germinating wheat embryos. There have been detailed studies of germin structure, biosynthesis, homology with other proteins, and of its value as a marker of wheat development. Germin isoforms associated with the apoplast have been speculated to have a role in embryo hydration during maturation and germination. Antigenically related isoforms of germin are present during germination in all of the economically important cereals studied, and the amounts of germin-like proteins and coding elements have been found to undergo conspicuous change when salt-tolerant higher plants are subjected to salt stress. In this report, we describe how circumstantial evidence arising from unrelated studies of barley oxalate oxidase and its coding elements have led to definitive evidence that the germin isoform made during wheat germination is an oxalate oxidase. Establishment of links between oxalate degradation, cereal germination, and salt tolerance has significant implications for a broad range of studies related to development and adaptation in higher plants. Roles for germin in cell wall biochemistry and tissue remodeling are discussed, with special emphasis on the generation of hydrogen peroxide during germin-induced oxidation of oxalate.

Amino Acid Sequence↗
PubMed2006

Predicting germination response to temperature. II. Three-dimensional regression, statistical gridding and iterative-probit optimization using measured and interpolated-subpopulation data.

BACKGROUND AND AIMS: Most current thermal-germination models are parameterized with subpopulation-specific rate data, interpolated from cumulative-germination-response curves. The purpose of this study was to evaluate the relative accuracy of three-dimensional models for predicting cumulative germination response to temperature. Three-dimensional models are relatively more efficient to implement than two-dimensional models and can be parameterized directly with measured data. METHODS: Seeds of four rangeland grass species were germinated over the constant-temperature range of 3 to 38 degrees C and monitored for subpopulation variability in germination-rate response. Models for estimating subpopulation germination rate were generated as a function of temperature using three-dimensional regression, statistical gridding and iterative-probit optimization using both measured and interpolated-subpopulation data as model inputs. KEY RESULTS: Statistical gridding is more accurate than three-dimensional regression and iterative-probit optimization for modelling germination rate and germination time as a function of temperature and subpopulation. Optimization of the iterative-probit model lowers base-temperature estimates, relative to two-dimensional cardinal-temperature models, and results in an inability to resolve optimal-temperature coefficients as a function of subpopulation. Residual model error for the three-dimensional model was extremely high when parameterized with measured-subpopulation data. Use of measured data for model evaluation provided a more realistic estimate of predictive error than did evaluation of the larger set of interpolated-subpopulation data. CONCLUSIONS: Statistical-gridding techniques may provide a relatively efficient method for estimating germination response in situations where the primary objective is to estimate germination time. This methodology allows for direct use of germination data for model parameterization and automates the significant computational requirements of a two-dimensional piece-wise-linear model, previously shown to produce the most accurate estimates of germination time.

Elymus↗
PubMed2006

Effect of light on seed germination of eight wetland Carex species.

BACKGROUND AND AIMS: In wetland plant communities, species-specific responses to pulses of white light and to red : far-red light ratios can vary widely and influence plant emergence from the seed bank. Carex species are the characteristic plants of sedge meadows of natural prairie wetlands in mid-continental USA but are not returning to restored wetlands. Little is known about how light affects seed germination in these species-information which is necessary to predict seed bank emergence and to develop optimal revegetation practices. The effects of light on germination in eight Carex species from prairie wetlands were investigated. METHODS: Non-dormant seeds of eight Carex species were used to determine the influence of light on germination by examining: (a) the ability of Carex seeds to germinate in the dark; (b) the effect of different lengths of exposures to white light on germination; (c) whether the effect of white light can be replaced by red light; and (d) whether the germination response of Carex seeds to white or red light is photoreversible by far-red light. KEY RESULTS: Seeds of C. brevior and C. stipata germinated >25 % in continuous darkness. Germination responses after exposure to different lengths of white light varied widely across the eight species. Carex brevior required <15 min of white light for > or =50 % germination, while C. hystericina, C. comosa, C. granularis and C. vulpinoidea required > or =8 h. The effect of white light was replaced by red light in all species. The induction of germination after exposure to white or red light was reversed by far-red light in all species, except C. stipata. CONCLUSIONS: The species-specific responses to simulated field light conditions suggest that (a) the light requirements for germination contribute to the formation of persistent seed banks in these species and (b) in revegetation efforts, timing seed sowing to plant community development and avoiding cover crops will improve Carex seed germination.

Carex Plant↗
PubMed2001

A mechanism for promoting the germination of Zinnia elegans seeds by hydrogen peroxide.

H(2)O(2) promotes seed germination of cereal plants such as barley, wheat and rice, and several mechanisms have been proposed for its action [Naredo et al. (1998) Seed Sci. Technol. 26: 675-689]. We investigated the role of H(2)O(2) in the germination of Zinnia elegans seeds. H(2)O(2) promoted seed germination in a dose-dependent manner as did respiratory inhibitors, indicating that H(2)O(2) itself possibly promotes seed germination rather than O(2). Seed germination was promoted by removal of pericarp from seeds or by removal of ethanol-soluble compounds from the seeds with pericarp. The ethanol-soluble compounds suppressed the germination of seeds having no pericarp, and this effect was reversed by H(2)O(2). These findings indicate that oxidation of the germination inhibitor(s) present in the pericarp by H(2)O(2) promotes seed germination. Antioxidants which are derivatives of well-known germination inhibitors suppressed seed germination in a dose-dependent manner, suggesting that, to initiate seed germination, a germination inhibitor(s) should be decomposed by an oxidant such as H(2)O(2).

Antioxidants↗
PubMed2002

Genetic and physiological analysis of germination efficiency in maize in relation to nitrogen metabolism reveals the importance of cytosolic glutamine synthetase.

We have developed an approach combining physiology and quantitative genetics to enhance our understanding of nitrogen (N) metabolism during kernel germination. The physiological study highlighted the central role of glutamine (Gln) synthetase (GS) and Gln synthesis during this developmental process because a concomitant increase of both the enzyme activity and the amino acid content was observed. This result suggests that Gln is acting either as a sink for ammonium released during both storage protein degradation and amino acid deamination or as a source for amino acid de novo synthesis by transamination. In the two parental lines used for the quantitative genetics approach, we found that the increase in Gln occurred earlier in Io compared with F(2), a result consistent with its faster germinating capacity. The genetic study was carried out on 140 F6 recombinant inbred lines derived from the cross between F(2) and Io. Quantitative trait locus mapping identified three quantitative trait loci (QTLs) related to germination trait (T50, time at which 50% of the kernels germinated) that explain 18.2% of the phenotypic variance; three QTLs related to a trait linked to germination performance, kernel size/weight (thousand kernels weight), that explain 17% of the phenotypic variance; two QTLs related to GS activity at early stages of germination that explain 17.7% of the phenotypic variance; and one QTL related to GS activity at late stages of germination that explains 7.3% of the phenotypic variance. Coincidences of QTL for germination efficiency and its components with genes encoding cytosolic GS (GS1) and the corresponding enzyme activity were detected, confirming the important role of the enzyme during the germination process. A triple colocalization on chromosome 4 between gln3 (a structural gene encoding GS1) and a QTL for GS activity and T50 was found; whereas on chromosome 5, a QTL for GS activity and thousand kernels weight colocalized with gln4, another structural gene encoding GS1. This observation suggests that for each gene, the corresponding enzyme activity is of major importance for germination efficiency either through the size of the grain or through its faster germinating capacity. Consistent with the possible nonoverlapping function of the two GS1 genes, we found that in the parental line Io, the expression of Gln3 was transiently enhanced during the first hours of germination, whereas that of gln4 was constitutive.

Chromosome Mapping↗