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At least 469 records · Page 26Linked to original sources
PubMed2004

Light induces phenylpropanoid metabolism in Arabidopsis roots.

Experiments have shown that many phenylpropanoid genes are highly expressed in light-grown Arabidopsis roots. Studies employing reporter gene constructs have indicated that the expression of these genes is localized not only to the lignifying root vasculature, but also to non-lignifying tissues, such as the root cortex, suggesting that the proteins encoded by these genes may be involved in aspects of phenylpropanoid metabolism other than lignification. Consistent with this hypothesis, roots of etiolated and soil-grown plants contain almost no soluble phenylpropanoids, but exposure to light leads to the accumulation of flavonoids, as well as high levels of coniferin and syringin (coniferyl and sinapyl-4-O-glycosides), compounds not previously reported to be accumulated in Arabidopsis. To elucidate the mechanism by which light induces root secondary metabolism, extracts of mutants defective in light perception and light responses were analyzed for phenylpropanoid content. The results of these assays showed that phytochrome (PHY)B and cryptochrome (CRY)2 are the primary photoreceptors involved in light-dependent phenylpropanoid accumulation, and that the hypocotyl elongated (HY5) transcription factor is also required for this response. The presence of phenylpropanoids in etiolated roots of cop (constitutively photomorphogenic)1, cop9, and det (de-etiolated)1 mutants indicate that the corresponding wild-type genes are required to repress root phenylpropanoid biosynthesis in the absence of light. Biochemical analysis of root cell walls and analysis of phenylpropanoid gene expression suggest that coniferin and syringin accumulation may be the result of both increased biosynthesis and decreased conversion of these compounds into other phenylpropanoid end products. Finally, our data suggest that the accumulation of coniferin, syringin, and flavonoids in Arabidopsis roots is a high-irradiance response (HIR), and suggest that comparative analysis of light- and dark-grown Arabidopsis roots may provide new insights into both phenylpropanoid biosynthesis and light signaling in plants.

Arabidopsis↗
PubMed2000

Basipetal auxin transport is required for gravitropism in roots of Arabidopsis.

Auxin transport has been reported to occur in two distinct polarities, acropetally and basipetally, in two different root tissues. The goals of this study were to determine whether both polarities of indole-3-acetic acid (IAA) transport occur in roots of Arabidopsis and to determine which polarity controls the gravity response. Global application of the auxin transport inhibitor naphthylphthalamic acid (NPA) to roots blocked the gravity response, root waving, and root elongation. Immediately after the application of NPA, the root gravity response was completely blocked, as measured by an automated video digitizer. Basipetal [(3)H]IAA transport in Arabidopsis roots was inhibited by NPA, whereas the movement of [(14)C]benzoic acid was not affected. Inhibition of basipetal IAA transport by local application of NPA blocked the gravity response. Inhibition of acropetal IAA transport by application of NPA at the root-shoot junction only partially reduced the gravity response at high NPA concentrations. Excised root tips, which do not receive auxin from the shoot, exhibited a normal response to gravity. The Arabidopsis mutant eir1, which has agravitropic roots, exhibited reduced basipetal IAA transport but wild-type levels of acropetal IAA transport. These results support the hypothesis that basipetally transported IAA controls root gravitropism in Arabidopsis.

Arabidopsis↗
PubMed1992

Growth and Movement of Spot Inoculated Rhizobium meliloti on the Root Surface of Alfalfa.

Inoculum droplets of approximately 10 nanoliter volume and containing about 10 Rhizobium meliloti cells were placed onto the root surface of alfalfa seedlings in plastic growth pouches at either the root tip, the position of the smallest emergent root hairs, or at a site midway between these points. The droplets were initially confined to an area of about 0.2 square millimeter at the point of application. By 48 and 96 hours after inoculation, the inoculum bacteria and their progeny were distributed over several centimeters of the root between the initial site of deposition and the growing root tip, reaching densities of 10(3) to 10(4) bacteria per centimeter near the site of initial deposition and decreasing exponentially from that point toward the root tip. Graphite particles deposited on the root surface close to the growing tip were similarly distributed along the root length by 48 and 96 hours, suggesting that passive displacement by root cell elongation was primarily responsible for the spread of bacteria. A nonmotile mutant of R. meliloti colonized alfalfa roots to the same extent as the wild type and was usually distributed in the same manner, indicating that bacterial motility contributed little under these conditions to long distance spread of the bacteria. However, when applied in low numbers, R. meliloti mutants defective in motility or chemotaxis were considerably less efficient in initiating nodules near the point of inoculation than the wild type. This implies that motility and/or chemotaxis contribute significantly to local exploration for suitable infection sites. Almost all nodules on the primary root formed within a few millimeters of the spot-inoculation site, indicating that, under our experimental conditions, movement and multiplication of R. meliloti on the root surface were not sufficient to maintain an adequate population in the infectible region of the root during root growth.

Journal Article↗
PubMed2001

Iron stress-induced changes in root epidermal cell fate are regulated independently from physiological responses to low iron availability.

Iron-overaccumulating mutants were investigated with respect to changes in epidermal cell patterning and root reductase activity in response to iron starvation. In all mutants under investigation, ferric chelate reductase activity was up-regulated both in the presence and absence of iron in the growth medium. The induction of transfer cells in the rhizodermis appeared to be iron regulated in the pea (Pisum sativum L. cv Dippes Gelbe Viktoria and cv Sparkle) mutants bronze and degenerated leaflets, but not in roots of the tomato (Lycopersicon esculentum Mill. cv Bonner Beste) mutant chloronerva, suggesting that in chloronerva iron cannot be recognized by putative sensor proteins. Experiments with split-root plants supports the hypothesis that Fe(III) chelate reductase is regulated by a shoot-borne signal molecule, communicating the iron status of the shoot to the roots. In contrast, the formation of transfer cells was dependent on the local concentration of iron, implying that this shoot signal does not affect their formation. Different repression curves of the two responses imply that the induction of transfer cells occurs after the enhancement of electron transfer across the plasma membrane rather than being causally linked. Similar to transfer cells, the formation of extra root hairs in the Arabidopsis mutant man1 was regulated by the iron concentration of the growth medium and was unaffected by interorgan signaling.

FMN Reductase↗
PubMed2001

Role of root hairs and lateral roots in silicon uptake by rice.

The rice plant (Oryza sativa L. cv Oochikara) is known to be a Si accumulator, but the mechanism responsible for the high uptake of Si by the roots is not well understood. We investigated the role of root hairs and lateral roots in the Si uptake using two mutants of rice, one defective in the formation of root hairs (RH2) and another in that of lateral roots (RM109). Uptake experiments with nutrient solution during both a short term (up to 12 h) and relatively long term (26 d) showed that there was no significant difference in Si uptake between RH2 and the wild type (WT), whereas the Si uptake of RM109 was much less than that of WT. The number of silica bodies formed on the third leaf in RH2 was similar to that in WT, but the number of silica bodies in RM109 was only 40% of that in WT, when grown in soil amended with Si under flooded conditions. There was also no difference in the shoot Si concentration between WT and RH2 when grown in soil under upland conditions. Using a multi-compartment transport box, the Si uptake at the root tip (0-1 cm, without lateral roots and root hairs) was found to be similar in WT, RH2, and RM109. However, the Si uptake in the mature zone (1-4 cm from root tip) was significantly lower in RM109 than in WT, whereas no difference was found in Si uptake between WT and RH2. All these results clearly indicate that lateral roots contribute to the Si uptake in rice plant, whereas root hairs do not. Analysis of F(2) populations between RM109 and WT showed that Si uptake was correlated with the presence of lateral roots and that the gene controlling formation of lateral roots and Si uptake is a dominant gene.

Cell Surface Extensions↗
PubMed1996

Characterization of the lipopolysaccharides from Rhizobium meliloti strain 102F51 and its nonnodulating mutant WL113.

Lipopolysaccharides from the Rhizobium meliloti wild-type strain 102F51, which is effective in symbiosis with alfalfa, and from the nonnodulating mutant WL113, defective in root hair adhesion, derived thereof, were isolated and comparatively analyzed. Both preparations were composed of galactose, glucose, glucuronic acid, galacturonic acid, glucosamine, 3-deoxyheptulosaric acid, and 2-keto-3-deoxyoctonic acid as the major sugar constitutents. After a modified methylation analysis (consisting of the following consecutive steps: methylation, carboxyl reduction, remethylation, mild acid hydrolysis, reduction, and trideuterio-methylation), all of the 3-deoxyheptulosaric and some of the 2-keto-3-deoxyoctonic acid residues were converted into their corresponding 3-deoxyalditol derivatives, which carried trideuteriomethyl groups at positions C-2, C-4, and C-6. Another part of the permethylated 3-deoxyoctitol was also found as 2,5,6- and 2,6,8-tri-O-trideuteriomethyl derivatives. NMR data obtained with the separated oligosaccharides and the results of methylation analysis indicated that the majority of 2-keto-3-deoxyoctonate was present in the fraction of permethylated disaccharide alditols, namely as 6-O-CD3-alpha Glc(1-->5)3-deoxyoctitol, 6-O-CD3-beta GlcNMeAcyl(1-->4)-3-deoxyoctitol, and as the permethylated trisaccharide alditol, alpha GalA(1-->3)-[6-O-CD3]-beta-Glc(1-->5)-[4-O-CD3]-3-deoxyoctitol. The presence of trideuteriomethyl groups at C-4 of both 3-deoxyalditols and at C-6 of the glucosaminyl or glycosyl residues indicated the linkage points of the released acid-labile ketosidic substituents, such as 3-deoxyheptulosarate and 2-keto-3-deoxyoctonate, in these oligosaccharides. The main differences between the preparations from the wild-type 102F51 and its mutant strain WL 113 were found in the higher content (in strain 102F51) of the following oligosaccharides: alpha-glucuronosyl(1-->4)2-keto-3-deoxyoctonate and alpha-galacturonosyl-(1-->3)alpha-glucosyl-(1-->5)2-keto-3-deoxyoc tonate and in the decreased content of beta-glucosaminyl(1-->4)2-keto-3-deoxy-octonate.

Lipopolysaccharides↗
PubMed2001

A gain-of-function mutation in IAA28 suppresses lateral root development.

The phytohormone auxin is important in many aspects of plant development. We have isolated an auxin-resistant Arabidopsis mutant, iaa28-1, that is severely defective in lateral root formation and that has diminished adult size and decreased apical dominance. The iaa28-1 mutant is resistant to inhibition of root elongation by auxin, cytokinin, and ethylene, but it responds normally to other phytohormones. We identified the gene defective in the iaa28-1 mutant by using a map-based positional approach and found it to encode a previously uncharacterized member of the Aux/IAA gene family. IAA28 is preferentially expressed in roots and inflorescence stems, and in contrast to other Aux/IAA genes, IAA28 transcription is not induced by exogenous auxin. Studies of the gain-of-function iaa28-1 mutant suggest that IAA28 normally represses transcription, perhaps of genes that promote lateral root initiation in response to auxin signals.

Amino Acid Sequence↗
PubMed2006

Analysis of the root-hair morphogenesis transcriptome reveals the molecular identity of six genes with roles in root-hair development in Arabidopsis.

Root-hair morphogenesis is a model for studying the genetic regulation of plant cell development, and double-mutant analyses have revealed a complex genetic network underlying the development of this type of cell. Therefore, to increase knowledge of gene expression in root hairs and to identify new genes involved in root-hair morphogenesis, the transcriptomes of the root-hair differentiation zone of wild-type (WT) plants and a tip-growth defective root-hair mutant, rhd2-1, were compared using Affymetrix ATH1 GeneChips. A set of 606 genes with significantly greater expression in WT plants defines the 'root-hair morphogenesis transcriptome'. Compared with the whole genome, this set is highly enriched in genes known to be involved in root-hair morphogenesis. The additional gene families and functional groups enriched in the root-hair morphogenesis transcriptome are cell wall enzymes, hydroxyproline-rich glycoproteins (extensins) and arabinogalactan proteins, peroxidases, receptor-like kinases and proteins with predicted glycosylphosphatidylinositol (GPI) anchors. To discover new root-hair genes, 159 T-DNA insertion lines identified from the root-hair morphogenesis transcriptome were screened for defects in root-hair morphogenesis. This identified knockout mutations in six genes (RHM1-RHM6) that affected root-hair morphogenesis and that had not previously been identified at the molecular level: At2g03720 (similar to Escherichia coli universal stress protein); At3g54870 (armadillo-repeat containing kinesin-related protein); At4g18640 (leucine-rich repeat receptor-like kinase subfamily VI); At4g26690 (glycerophosphoryl diester phosphodiesterase-like GPI-anchored protein); At5g49270 (COBL9 GPI-anchored protein) and At5g65090 (inositol-1,4,5 triphosphate 5-phosphatase-like protein). The mutants were transcript null, their root-hair phenotypes were characterized and complementation testing with uncloned root-hair genes was performed. The results suggest a role for GPI-anchored proteins and lipid rafts in root-hair tip growth because two of these genes (At4g26690 and At5g49270) encode predicted GPI-anchored proteins likely to be associated with lipid rafts, and several other genes previously shown to be required for root-hair development also encode proteins associated with sterol-rich lipid rafts.

Arabidopsis↗
PubMed1996

A quadruple mutant T4 RNA hairpin with the same structure as the wild-type translational repressor.

The solution structure of a 16-nucleotide RNA hairpin, 5'-GCCUAG[CAAC]CUGGGC (loop bases in square brackets), has been determined by proton, phosphorus, and carbon (natural abundance) nuclear magnetic resonance (NMR) spectroscopy. This RNA tetraloop hairpin varies in four loop nucleotides from the wild-type T4 RNA hairpin (with eight loop nucleotides) involved in the translational repression of bacteriophage T4 DNA polymerase. Despite the differences in their sequence and proposed secondary structures, these two hairpins bind T4 DNA polymerase with equal affinity. The NMR spectra of the mutant hairpin indicate that its stem is extended in comparison to that of the wild-type hairpin by the formation of two additional Watson-Crick base pairs. The NMR data provide a precisely defined structure for the mutant hairpin with an average root mean square deviation of approximately 0.7 A for all 16 residues in the molecule. The structure of the mutant loop is very similar to that determined previously for the wild-type hairpin. The three loop bases that are conserved between the mutant and wild-type hairpins point out in solution with the groups capable of hydrogen bond formation exposed to the solution. This is exactly what was seen for the wild-type hairpin. Also, unusual, long-range NOEs, loop hydrogen bonds, and even the position at which the loop bends are common features between the two loops. This explains how two different hairpins, by adopting similar three-dimensional structures, have the same affinity for the DNA polymerase.

Bacteriophage T4↗
PubMed2005

Down regulation of virulence factors of Pseudomonas aeruginosa by salicylic acid attenuates its virulence on Arabidopsis thaliana and Caenorhabditis elegans.

Salicylic acid (SA) is a phenolic metabolite produced by plants and is known to play an important role in several physiological processes, such as the induction of plant defense responses against pathogen attack. Here, using the Arabidopsis thaliana-Pseudomonas aeruginosa pathosystem, we provide evidence that SA acts directly on the pathogen, down regulating fitness and virulence factor production of the bacteria. Pseudomonas aeruginosa PA14 showed reduced attachment and biofilm formation on the roots of the Arabidopsis mutants lox2 and cpr5-2, which produce elevated amounts of SA, as well as on wild-type Arabidopsis plants primed with exogenous SA, a treatment known to enhance endogenous SA concentration. Salicylic acid at a concentration that did not inhibit PA14 growth was sufficient to significantly affect the ability of the bacteria to attach and form biofilm communities on abiotic surfaces. Furthermore, SA down regulated three known virulence factors of PA14: pyocyanin, protease, and elastase. Interestingly, P. aeruginosa produced more pyocyanin when infiltrated into leaves of the Arabidopsis transgenic line NahG, which accumulates less SA than wild-type plants. This finding suggests that endogenous SA plays a role in down regulating the synthesis and secretion of pyocyanin in vivo. To further test if SA directly affects the virulence of P. aeruginosa, we used the Caenorhabditis elegans-P. aeruginosa infection model. The addition of SA to P. aeruginosa lawns significantly diminished the bacterium's ability to kill the worms, without affecting the accumulation of bacteria inside the nematodes' guts, suggesting that SA negatively affects factors that influence the virulence of P. aeruginosa. We employed microarray technology to identify SA target genes. These analyses showed that SA treatment affected expression of 331 genes. It selectively repressed transcription of exoproteins and other virulence factors, while it had no effect on expression of housekeeping genes. Our results indicate that in addition to its role as a signal molecule in plant defense responses, SA works as an anti-infective compound by affecting the physiology of P. aeruginosa and ultimately attenuating its virulence.

Animals↗
PubMed2005

Severe reduction in growth rate and grain filling of rice mutants lacking OsGS1;1, a cytosolic glutamine synthetase1;1.

Rice (Oryza sativa L.) plants possess three homologous but distinct genes for cytosolic glutamine synthetase (GS1): these are OsGS1;1, OsGS1;2, and OsGS1;3. OsGS1;1 was expressed in all organs tested with higher expression in leaf blades, while OsGS1;2, and OsGS1;3 were expressed mainly in roots and spikelets, respectively. We characterized knockout mutants caused by insertion of endogenous retrotransposon Tos17 into the exon-8 (lines ND8037 and ND9801) or the exon-10 (line NC2327) of OsGS1;1. Mendelian segregation occurred in each progeny. Homozygously inserted mutants showed severe retardation in growth rate and grain filling when grown at normal nitrogen concentrations. Abnormal mRNA for GS1;1 was transcribed, and the GS1 protein and its activity in the leaf blades were barely detectable in these mutants. The glutamine pool in the roots and leaf blades of the mutants was lower than that of the wild type. Re-introduction of OsGS1;1 cDNA under the control of its own promoter into the mutants successfully complemented these phenotypes. Progeny where Tos17 was heterozygously inserted or deleted during segregation showed normal phenotypes. The results indicate that GS1;1 is important for normal growth and grain filling in rice; GS1;2 and GS1;3 were not able to compensate for GS1;1 function.

Gene Expression Profiling↗
PubMed2007

The floral volatile, methyl benzoate, from snapdragon (Antirrhinum majus) triggers phytotoxic effects in Arabidopsis thaliana.

Previously it has been shown that the floral scent of snapdragon flowers consists of a relatively simple mixture of volatile organic compounds (VOCs). These compounds are thought to be involved in the attraction of pollinators; however, little is known about their effect on other organisms, such as neighboring plants. Here, we report that VOCs from snapdragon flowers inhibit Arabidopsis root growth. Out of the three major snapdragon floral volatiles, myrcene, (E)-beta-ocimene, and methyl benzoate (MB), MB was found to be primarily responsible for the inhibition of root growth. Ten micromoles MB reduced root length by 72.6%. We employed a microarray approach to identify the MB target genes in Arabidopsis that were responsible for the root growth inhibition phenotype in response to MB. These analyses showed that MB treatment affected 1.33% of global gene expression, including cytokinin, auxin and other plant-hormone-related genes, and genes related to seed germination processes in Arabidopsis. Accordingly, the root growth of cytokinin (cre1) and auxin (axr1) response mutants was less affected than that of the wild type by the volatile compound: roots of the treated mutants were reduced by 45.1 and 56.2%, respectively, relative to untreated control mutants.

Antirrhinum↗
PubMed1985

Symbiotic mutants of Rhizobium meliloti that uncouple plant from bacterial differentiation.

Spontaneous mutants at a new symbiotic locus in Rhizobium meliloti SU47 are resistant to several phages and are conditionally insensitive to a monoclonal antibody to the bacterial surface, apparently because they are deficient in a wild-type exopolysaccharide. On alfalfa, the mutants do not curl root hairs, but penetrate the epidermis directly, forming nodules that contain no visible infection threads or "bacteroids," have a few bacteria in superficial intercellular spaces only and not within the nodule cells, and fail to fix nitrogen (Fix-). Evidently, infection threads are not essential for cell proliferation and nodule formation, which are here induced by a bacterial signal at a distance and uncoupled from the bacterial differentiation that normally goes on as well.

Antibodies, Monoclonal↗
PubMed2005

Structure of the thermolabile mutant aldolase B, A149P: molecular basis of hereditary fructose intolerance.

Hereditary fructose intolerance (HFI) is a potentially lethal inborn error in metabolism caused by mutations in the aldolase B gene, which is critical for gluconeogenesis and fructose metabolism. The most common mutation, which accounts for 53% of HFI alleles identified worldwide, results in substitution of Pro for Ala at position 149. Structural and functional investigations of human aldolase B with the A149P substitution (AP-aldolase) have shown that the mutation leads to losses in thermal stability, quaternary structure, and activity. X-ray crystallography is used to reveal the structural basis of these perturbations. Crystals of AP-aldolase are grown at two temperatures (4 degrees C and 18 degrees C), and the structure solved to 3.0 angstroms resolution, using the wild-type structure as the phasing model. The structures reveal that the single residue substitution, A149P, causes molecular disorder around the site of mutation (residues 148-159), which is propagated to three adjacent beta-strand and loop regions (residues 110-129, 189-199, 235-242). Disorder in the 110-129-loop region, which comprises one subunit-subunit interface, provides an explanation for the disrupted quaternary structure and thermal instability. Greater structural perturbation, particularly at a Glu189-Arg148 salt bridge in the active-site architecture, is observed in the structure determined at 18 degrees C, which could explain the temperature-dependent loss in activity. The disorder revealed in these structures is far greater than that predicted by homology modeling and underscores the difficulties in predicting perturbations of protein structure and function by homology modeling alone. The AP-aldolase structure reveals the molecular basis of a hereditary disease and represents one of only a few structures known for mutant proteins at the root of the thousands of other inherited disorders.

Binding Sites↗
PubMed1997

Cytoplasmic free calcium distributions during the development of root hairs of Arabidopsis thaliana.

In this study, confocal ratio analysis was used to image the relationship between cytoplasmic free calcium concentration ([Ca2+]c) and the development of root hairs of Arabidopsis thaliana. Although a localized change in [Ca2+]c that preceded or predicted the site of root hair initiation could not be detected, once initiated the majority of emerging root hairs showed an elevated [Ca2+]c (> 1 microM) in their apical cytoplasm, compared with 100-200 nM in the rest of the cell. These emerging root hairs then moved into a 3-5 h phase of sustained elongation during which they showed variable growth rates. Root hairs that were rapidly elongating exhibited a highly localized, elevated [Ca2+]c at the tip. Non-growing root hairs did not exhibit the [Ca2+]c gradient. The rhd-2 mutant, which is defective in sustained root hair growth, showed an altered [Ca2+]c distribution compared with wild-type. These results implicate [Ca2+]c in regulating the tip growth process. Treatment of elongating wild-type root hairs with the Ca2+ channel blocker verapamil (50 microM) caused dissipation of the elevated [Ca2+]c at the tip and cessation of growth, suggesting a requirement for Ca2+ channel activity at the root hair tip to maintain growth. Manganese treatment also preferentially quenched Indo-1 fluorescence in the apical cytoplasm of the root hair. As manganese is thought to enter cells through Ca(2+)-permeable channels, this result also suggests increased Ca2+ channel activity at the tip of the growing hair. Taken together, these data suggest that although Ca2+ does not trigger the initiation of root hairs, Ca2+ influx at the tip of the root hair leads to an elevated [Ca2+]c that may be required to sustain root hair elongation.

Arabidopsis↗
PubMed2002

Involvement of the VEP1 gene in vascular strand development in Arabidopsis thaliana.

A dominant mutant line characterized by abnormal leaf venation pattern was isolated from a transgenic Arabidopsis plant pool that was generated with Agrobacterium culture harboring an Arabidopsis antisense cDNA library. In the mutant line, the phenotype was due to antisense suppression of a gene we named VEP1 (Vein Patterning). The predicted amino acid sequence of the gene contained a motif related to the mammalian death domain that is found in the apoptotic machinery. Reduced expression of the VEP1 gene resulted in the reduced complexity of the venation pattern of the cotyledons and foliar leaves, which was mainly due to the reduced number of the minor veins and their incomplete connection. The analysis of mutant embryos indicated that the phenotype was originated, at least in part, from a defect in the procambium patterning. In the mutant, the stem and root were thinner than those in wild type. This phenotype was associated with reduced vascular development. The promoter activity of the VEP1 gene was detected preferentially in the vascular regions. We propose that the death domain-containing protein VEP1 functions as a positive element required for vascular strand development in Arabidopsis thaliana.

Amino Acid Sequence↗
PubMed2004

Arabidopsis trehalose-6-phosphate synthase 1 is essential for normal vegetative growth and transition to flowering.

In resurrection plants and yeast, trehalose has a function in stress protection, but the absence of measurable amounts of trehalose in other plants precludes such a function. The identification of a trehalose biosynthetic pathway in angiosperms raises questions on the function of trehalose metabolism in nonresurrection plants. We previously identified a mutant in the Arabidopsis trehalose biosynthesis gene AtTPS1. Plants homozygous for the tps1 mutation do not develop mature seeds (Eastmond et al., 2002). AtTPS1 expression analysis and the spatial and temporal activity of its promoter suggest that this gene is active outside the seed-filling stage of development as well. A generally low expression is observed in all organs analyzed, peaking in metabolic sinks such as flower buds, ripening siliques, and young rosette leaves. The arrested tps1/tps1 embryonic state could be rescued using a dexamethasone-inducible AtTPS1 expression system enabling generation of homozygous mutant plants. When depleted in AtTPS1 expression, such mutant plants show reduced root growth, which is correlated with a reduced root meristematic region. Moreover, tps1/tps1 plants are retarded in growth and remain generative during their lifetime. Absence of Trehalose-6-Phosphate Synthase 1 in Arabidopsis plants precludes transition to flowering.

Arabidopsis↗