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PubMed2006

The strawberry gene FaGAST affects plant growth through inhibition of cell elongation.

The strawberry (Fragaria x ananassa) FaGAST gene encodes a small protein with 12 cysteine residues conserved in the C-terminal region similar to a group of proteins identified in other species with diverse assigned functions such as cell division, elongation, or elongation arrest. This gene is expressed in the fruit receptacle, with two peaks during ripening at the white and the red-ripe stages, both coincident with an arrest in the growth pattern. Expression is also high in the roots but confined to the cells at the end of the elongation zone. Exogenous application of gibberellin increased the transcript level of the FaGAST gene in strawberry fruits. Ectopic expression of FaGAST in transgenic Fragaria vesca under the control of the CaMV-35S promoter caused both delayed growth of the plant and fruits with reduced size. The same growth defect was observed in Arabidopsis thaliana plants overexpressing FaGAST. In addition, the transgenic plants exhibited late flowering and low sensitivity to exogenous gibberellin. Taken together, the expression pattern, the regulation by gibberellin, and the transgenic phenotypes point to a role for FaGAST in arresting cell elongation during strawberry fruit ripening.

Arabidopsis↗

PubMed2001

A comparative molecular-physiological study of submergence response in lowland and deepwater rice.

Survival of rice (Oryza sativa) upon an extreme rise of the water level depends on rapid stem elongation, which is mediated by ethylene. A genomic clone (OS-ACS5) encoding 1-aminocyclopropane-1-carboxylic acid (ACC) synthase, which catalyzes a regulatory step in ethylene biosynthesis, has been isolated from cv IR36, a lowland rice variety. Expression was induced upon short- and long-term submergence in cv IR36 and in cv Plai Ngam, a Thai deepwater rice variety. Under hypoxic conditions, abscisic acid and gibberellin had a reciprocal opposite effect on the activity of OS-ACS5. Gibberellin up-regulated and abscisic acid down-regulated OS-ACS5 mRNA accumulation. Growth experiments indicated that lowland rice responded to submergence with a burst of growth early on, but lacked the ability to sustain elongation growth. Sustained growth, characteristic for deepwater rice, was correlated with a prolonged induction of OS-ACS5. In addition, a more pronounced capacity to convert ACC to ethylene, a limited ACC conjugation, and a high level of endogenous gibberellin(20) were characteristic for the deepwater variety. An elevated level of OS-ACS5 messenger was found in cv IR36 plants treated with exogenous ACC. This observation was concomitant with an increase in the capacity of converting ACC to ethylene and in elongation growth, and resulted in prolonged survival. In conclusion, OS-ACS5 is involved in the rapid elongation growth of deepwater rice by contributing to the initial and long-term increase in ethylene levels. Our data also suggest that ACC limits survival of submerged lowland rice seedlings.

Agriculture↗

PubMed1968

Native growth inhibitors from citrus shoots. Partition, bioassay, and characterization.

A partition method has been devised to separate auxins, gibberellins, and their respective inhibitors in plant extracts. Inhibitors counteracting gibberellin activity have been detected by a modified barley endosperm bioassay. An inhibitor found in young citrus shoots counteracts both auxin and gibberellin activities and behaves during partition and ohromatography like abscisin II.

Journal Article↗

PubMed1968

Regulation of Cold Hardiness in Acer negundo.

The application of gibberellin to Acer negundo either during or after a short photoperiod strikingly lowered the amount of hardiness obtained after 4 weeks in darkness at 5 degrees . Two growth retardants, B9 and Amo 1618, the latter of which interferes with gibberellin synthesis, brought about hardiness increases under long photoperiods. The naturally occurring inhibitor, dormin, also increased hardiness under the usual inhibiting influence of long photo-periods. Extracts from plants given long or short days had gibberellin-like compounds in largest quantities during LD and lowest quantities under SD, while the inverse was true for the inhibitor.

Journal Article↗

PubMed1969

Characterization and Role of an Endogenous Inhibitor in the Induction of Cold Hardiness in Acer negundo.

An inhibitor extracted from short day treated Acer negundo leaves was compared to abscisic acid in 4 different solvent systems. The chromatographic properties of abscisic acid and the inhibitor were in very close agreement. Treatment of Acer negundo plants under non-hardening preconditions (long days) with either the inhibitor or abscisic acid increased hardiness after a hardening period of 3 weeks at 40 degrees . A gibberellin-inhibitor relationship was further studied by making comparison of extracts of plants subjected to either 4 weeks of long days, long days + 5 degrees nights, or short days. These tests indicated that gibberellin-like activity was greatest when the treatment included long days. Abscisic acid-like levels were highest when the treatments consisted of short days or long days + 5 degrees nights. Since the latter groups are the most capable of developing hardiness, the hardening process appears to be more closely related to a build-up of abscisic acid levels than a reduction of gibberellin levels.

Journal Article↗

PubMed1970

Regulation of Bud Rest in Tubers of Potato, Solanum tuberosum L: VII. Effect of Abscisic and Gibberellic Acids on Nucleic Acid Synthesis in Excised Buds.

The effect of gibberellin A(3) (10(-4)m) and abscisic acid (10(-4)m), applied separately and together, on incorporation of (3)H-thymidine and (3)H-uridine into DNA and RNA of buds from freshly harvested potatoes was investigated. In some treatments apical buds in intact tubers were treated three times daily for 3 days with test solution before the buds were excised and treated an additional 12 hours in Petri dishes. In other treatments, untreated buds were excised and treated 12 hours. Irrespective of length of treatment, gibberellin A(3) slightly promoted synthesis of DNA and RNA, and abscisic acid essentially blocked such synthesis, in both the presence and absence of gibberellin A(3).

Journal Article↗

PubMed1974

Actions of gibberellic Acid and phytochrome on the germination of grand rapids lettuce seeds.

Red light and gibberellic acid were about equally effective in promoting germination of Grand Rapids lettuce (Lactuca sativa L.) seeds. With initial far red light treatment more than 80% remained dormant in subsequent dark storage. After 2 days of dark storage, red light effectively promoted germination, while gibberellic acid action was weak. With between 2 and 10 days of dark storage, gibberellic acid had little effect, while promotion by red light decreased slowly and finally disappeared. After 10 days of dark storage, both gibberellic acid and red light were required for germination. The dark storage treatment interferes with phytochrome-independent germination processes and cannot be overcome by added gibberellic acid. However, storage may also decrease the effectiveness of endogenous gibberellins. Phytochrome-dependent germination seems to require only low levels of endogenous gibberellin activity or the addition of gibberellic acid. Gibberellins and red light appear to act on germination by regulation of sequential sites of a branched-looped pathway.

Journal Article↗

PubMed1983

Internode length in pisum: do the internode length genes effect growth in dark-grown plants?

Internode length in light-grown peas (Pisum sativum L.) is controlled by the interaction of genes occupying at least five major loci, Le, La, Cry, Na, and Lm. The present work shows that the genes at all of the loci examined (Le, Cry, and Na) also exert an effect on internode length in plants grown in complete darkness. Preliminary results using pure lines were verified using either segregating progenies or near isogenic lines. The major cause of the differences was due to a change in the number of cells per internode rather than to an alteration of the cell length. Since the genes occupying at least two of these loci, Le and Na, have been shown to be directly involved with gibberellin metabolism, it appears that gibberellins are not only essential for elongation in the dark but are limiting for elongation in the nana (extremely short, na), dwarf (Na le), and tall (Na Le) phenotypes. These results are supported by the large inhibitory effects of AMO 1618 treatments on stem elongation in dwarf and tall lines grown in the dark and the fact that applied gibberellic acid could overcome this inhibition and greatly promote elongation in a gibberellin-deficient na line. It is clear that the internode length genes, and in particular the alleles at the Le locus, are not acting by simply controlling the sensitivity of the plant to light.

Journal Article↗

PubMed1990

Comparative indole-3-acetic Acid levels in the slender pea and other pea phenotypes.

Free indole-3-acetic acid levels were measured by gas chromatography-mass spectrometry in three ultra-tall ;slender' Pisum sativum L. lines differing in gibberellin content. Measurements were made for apices and stem elongation zones of light-grown plants and values were compared with wild-type, dwarf, and nana phenotypes in which internode length is genetically regulated, purportedly via the gibberellin level. Indole-3-acetic acid levels of growing stems paralleled growth rates in all lines, and were high in all three slender genotypes. Growth was inhibited by p-chlorophenoxyisobutyric acid, demonstrating the requirement of auxin activity for stem elongation, and also by the ethylene precursor 1-aminocyclopropane-1-carboxylic acid. It is concluded that the slender phenotype may arise from constant activation of a gibberellin receptor or transduction chain event leading directly or indirectly to elevated levels of indole-3-acetic acid, and that increased indole-3-acetic acid levels are a significant factor in the promotion of stem elongation.

Journal Article↗

PubMed1991

Determination of the Cellular Mechanisms Regulating Thermo-Induced Stem Growth in Thlaspi arvense L.

Field pennycress (Thlaspi arvense L.) is a species with a cold requirement for the initiation of reproductive development (thermoinduction). Work in this laboratory has been focused on elucidating the biochemical and molecular mechanisms underlying the bolting or rapid stem elongation response that is an intricate part of reproductive development in this species. In the present paper the cellular basis for thermo-induced stem growth was determined. Evidence is presented indicating that bolting results from the production of new cells that elongate to their original length before thermoinduction. This increase in cell division occurs in the pith and cortex approximately 0.5 to 5.0 millimeters below the stem apex. For at least the early stages of thermo-induced stem growth, enhanced cell elongation does not appear to be a factor because average lengths of pith cells from stems of thermo-induced plants were similar or less than noninduced controls. In addition, both the amount of increase in the production of new pith cells and stem growth were positively correlated with the length of the cold treatment. Two other lines of evidence are presented corroborating previous assertions (JD Metzger [1985] Plant Physiol 78: 8-13) that gibberellins mediate thermo-induced stem growth in field pennycress. First, treatment of noninduced plants with gibberellin A(3) completely mimicked the effects of a 4-week cold treatment on mitotic activity in the pith and cortex. Second, very little increase in the production of new cells was observed in the pith and cortex of thermo-induced plants of a gibberellin-deficient dwarf mutant of field pennycress. It is also shown that the influence of photoperiod on stem growth is mediated by an effect on the final length that cells ultimately attain.

Journal Article↗

PubMed2002

Mutations in the Dof zinc finger genes DAG2 and DAG1 influence with opposite effects the germination of Arabidopsis seeds.

We describe the Arabidopsis gene DAG2 encoding a Dof zinc finger protein and show that it is involved in the control of seed germination. An Arabidopsis mutant line with a T-DNA insertion in DAG2 isolated by reverse genetics produces seeds that are substantially more dependent than the wild type on the physical stimuli-light and cold treatment-that promote germination. Mutant dag2 seeds also are less sensitive to the germination-promotive effect of gibberellins, because a 10-fold higher amount of gibberellins is needed to restore germination when endogenous gibberellin biosynthesis is blocked. The seed germination characteristics of the dag2 mutant are opposite to those of dag1, a knockout mutant of another Dof gene (DAG1) that we showed previously to be involved in the control of seed germination, and are similar to those of plants that overexpress DAG1. The promoter of the DAG2 gene is active specifically in the vascular system of the mother plant but not in the embryo, and segregation analysis indicates that the effect of the dag2 mutation is maternal. Both characteristics are in common with DAG1; additionally, the DAG1 and DAG2 proteins share high sequence homology and an identical zinc finger domain. These data suggest, and the germination phenotype of the double mutant is compatible with, a model whereby the zinc finger proteins DAG1 and DAG2 act on a maternal switch that controls seed germination, possibly by regulating the same gene(s).

Arabidopsis↗

PubMed1979

Plant Growth Substances Produced by Azospirillum brasilense and Their Effect on the Growth of Pearl Millet (Pennisetum americanum L.).

Azospirillum brasilense, a nitrogen-fixing bacterium found in the rhizosphere of various grass species, was investigated to establish the effect on plant growth of growth substances produced by the bacteria. Thin-layer chromatography, high-pressure liquid chromatography, and bioassay were used to separate and identify plant growth substances produced by the bacteria in liquid culture. Indole acetic acid and indole lactic acid were produced by A. brasilense from tryptophan. Indole acetic acid production increased with increasing tryptophan concentration from 1 to 100 mug/ml. Indole acetic acid concentration also increased with the age of the culture until bacteria reached the stationary phase. Shaking favored the production of indole acetic acid, especially in a medium containing nitrogen. A small but biologically significant amount of gibberellin was detected in the culture medium. Also at least three cytokinin-like substances, equivalent to about 0.001 mug of kinetin per ml, were present. The morphology of pearl millet roots changed when plants in solution culture were inoculated. The number of lateral roots was increased, and all lateral roots were densely covered with root hairs. Experiments with pure plant hormones showed that gibberellin causes increased production of lateral roots. Cytokinin stimulated root hair formation, but reduced lateral root production and elongation of the main root. Combinations of indole acetic acid, gibberellin, and kinetin produced changes in root morphology of pearl millet similar to those produced by inoculation with A. brasilense.

Journal Article↗

PubMed2002

[Sedimentable amyloplasts in Japanese weeping cherry].

In branches of the upright type of Japanese cherry reacting on the gravity stimulation, tension wood were formed by the action of gibberellin in the secondary xylem and caused negative gravitropism [correction of gravitorpism]. In the other hand, in branches of the weeping type of Japanese cherry, gibberellin was almost used for the elongation of the tip region and the shortage of gibberellin in the supporting tissue caused on the lack of tension wood. The weeping branches were unable to support their own weight and elongated to downward. It has already reported that both the upright and the weeping types of Japanese cherry have sedimentable amyloplasts in the endodermal starch sheath cells. In this study, the endodermal starch sheath cells were examined to investigate the cause of abnormal gravi-response in branches of the weeping type of Japanese cherry. Current-year branches of both the upright and the weeping types of Prunus spachiana were used as materials. The amyloplasts in the weeping type sedimented toward the base of the branches elongating upward and toward the apex in the branches elongating downward. In both cases, the sedimentation was toward the gravity vector. Then, the amyloplasts of the weeping branches were re-sedimentated toward the vector of gravity after changing branch position mechanically to upward, same as the upright type. In electron microscope studies, it was showed that amyloplasts had the lamella structure and the endodermal starch sheath cells were filled with large vacuoles. Moreover, endoplasmic reticulum, which was noticed in organelle relating to the graviperception, distributed to the cell periphery and was not locally. It was not showed the cell polarity [correction of polality]. The fine structures of the endodermal starch sheath cell of both types of cherry were similar. These results suggest that the abnormality of the gravi-response in the weeping Prunus trees is not due to the abnormal development of gravi-sensor.

Cell Polarity↗

PubMedDate not supplied

[The dynamics of hormonal status of developing red beet root (Beta vulgaris L.) in correlation with the dynamics of sugar accumulation].

We studied the dynamics of phytohormone levels (indole-3-acetic acid, abscisic acid, cytokinins, and gibberellin-like substances) in red beet (Beta vulgaris L.) roots at different developmental stages in comparison with the data on the dynamics of sugar accumulation in order to test possible hormonal regulation of sugar accumulation. The obtained data suggest the involvement of cytokinins and gibberellin-like substances in the control of sugar accumulation in the roots, while indole-3-acetic acid, abscisic acid, and gibberellin-like substances can control the outflow. The data on the dynamics of phytohormone levels shed light on their specific physiological role in red beet root development.

Beta vulgaris↗

PubMed2025

Multi-Omics insights into OsZFP252-OsGA20ox5 mediated drought tolerance in rice through stomatal and vascular regulation.

Rice growth is highly dependent on water availability, and drought stress significantly impacts its entire life cycle. However, previous studies lack systematic investigations into drought-responsive candidate genes across the full life cycle of rice. This study integrates transcriptomic and phenotypic data from two rice lines, IR64 (drought-sensitive) and DK151 (drought-tolerant), under varied environmental conditions at distinct growth stages. Using k-means clustering, 13 369 genes were categorized into 17 distinct expression patterns, revealing drought-responsive genes specifically upregulated or downregulated under drought stress. Weighted co-expression network analysis (WGCNA) further identified four gene modules strongly correlated with drought-related phenotypes, co-localizing 2859 drought-responsive genes through both approaches. Proteomics and metabolomics were supplemented at the booting stage, where phenotypic and transcriptomic differences under drought were most pronounced. Integrated omics results demonstrate gibberellin (GA) and abscisic acid (ABA) pathways play a key role during drought tolerance in rice, and 79 high-confidence drought-resistant candidate genes were prioritized from the 2859 drought-responsive genes. Among these, Gibberellin 20-oxidase 5 (OsGA20ox5) was identified as a key negative regulator of drought tolerance. Furthermore, the transcription factor zinc finger protein 252 (OsZFP252) directly binds to the OsGA20ox5 promoter, repressing its expression and enhancing ABA biosynthesis, thereby improving drought tolerance by increasing stomatal closure and expanding vascular bundle water transport capacity. Notably, the drought-tolerant haplotype 2-4 (Hap2-4) of OsGA20ox5 provides valuable insights for drought-resistant breeding.

Oryza↗

PubMed2004

Characterization of a dwarf gene in Brassica rapa, including the identification of a candidate gene.

Dwarf genes have been valuable for improving harvestable yield of several crop plants and may be useful in oilseed Brassica. We evaluated a dwarf gene, dwf2, from Brassica rapa in order to determine its phenotypic effects and genetic characteristics. The dwf2 mutant was insensitive to exogenous GA(3) for both plant height and flowering time, suggesting that it is not a mutation in the gibberellin biosynthesis pathway. The dwarf phenotype was controlled by a semidominant allele at a single locus. Near-isogenic lines that were homozygous or heterozygous for dwf2 had 47.4% or 30.0% reduction in plant height, respectively, compared to the tall wild-type line, and the reduction was due to reduced internode length and number of nodes. The dwf2 homozygous and heterozygous lines had the same or significantly higher numbers of primary branches than the wild-type line, but did not differ in flowering time. The DWF2 gene was mapped to the bottom of linkage group R6, in a region having homology to the top of Arabidopsis thaliana chromosome 2. The map position of DWF2 in comparison to markers in A. thaliana suggests it is a homolog of RGA ( repressor of ga1-3), which is a homolog of the wheat "Green Revolution" gene. This dwarf gene could be used to gain more insight on the gibberellin pathway and to reduce lodging problems in hybrid oilseed Brassica cultivars.

Arabidopsis↗

PubMed1996

The isoprenoid pathway: cloning and characterization of fungal FPPS genes.

Farnesylpyrophosphate synthase (FPPS) is a key enzyme in isoprenoid biosynthesis. Several classes of essential metabolites, including sterols, quinones, carotenoids and gibberellins, are terpenoids with high biological activity. The structural gene for FPP synthase was isolated from two ascomycete fungi, Neurospora crassa and Gibberella fujikuroi. A comparative analysis of the nucleotide sequences of both FPPS genes revealed the presence of introns at the same positions at the 5' end of the coding regions. Furthermore, the most conserved region of the gene was isolated from two other plant pathogenic fungi, Sphaceloma manihoticola and Claviceps purpurea, by PCR. Sequence analysis showed a high degree of similarity between the deduced proteins of all known FPP synthase genes. In contrast to animals, all analyzed fungi contain a single copy of the gene, although FPP is the precursor for essential sterol and quinone biosynthesis and secondary metabolites, such as gibberellins, as well. Transcription analysis in different light regimes has shown that the FPPS genes in G. fujikuroi and N. crassa are not regulated by light induction.

Alkyl and Aryl Transferases↗

PubMed2006

Exogenous and endogenous growth regulators on apogamy in Dryopteris affinis (Lowe) Fraser-Jenkins sp. affinis.

This work showed for the first time the relationship between the effect of exogenous auxins and gibberellins on apogamy in Dryopteris affinis (Lowe) Fraser-Jenkins sp. affinis and its endogenous contents during early apogamic events. The addition of NAA (0.53 and 5.37 microM) or GA(3) 2.8 microM to an MS solid medium significantly increased apogamous sporophyte formation. BA induced brown callus that regenerated sporophytes in a hormone-free medium. The endogenous contents of GA(1), GA(3), GA(4), GA(7), GA(9) and IAA were determined by GC-MS in gametophytes cultured on MS solid medium, before and during early stages of apogamous embryo development. The accumulation of both GA(9) and IAA before embryo development was evident as high levels of GA(4) in the earliest analysed stage of embryo development and high levels of GA(3) in elongating shoots were found. The role of gibberellins on apogamy was also supported by data showing a decrease in the percentage of gametophytes developing embryos because of the addition of flurprimidol to the culture medium.

Dryopteris↗