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At least 613 records · Page 34Linked to original sources
PubMed2026

Integrated phenotype, endogenous hormones and transcriptome analysis revealed the mechanism of response of Phoebe bournei seedlings to shade signals.

Understory tree seedlings are subjected to prolonged shading stress imposed by the canopy foliage, which significantly impedes their growth. A hallmark of shaded environments is a reduced red to far-red light ratio (R: FR). This study elucidates the physiological and molecular responses of the endangered tree species Phoebe bournei to shading signals. Seedlings were exposed to white light (control) and simulated shading environments with R: FR ratios of 1.5, 0.8, and 0.2. The findings reveal that an increase in the proportion of far-red light significantly enhances seedling height, root-collar diameter, internode length, petiole length, leaf surface area, and leaf biomass. Differentially expressed genes (DEGs) in each treatment group predominantly enrich pathways associated with hormone signaling, stress responses, and photosynthesis. Validation experiments demonstrate that shading promotes the activity of Rubisco and RCA enzymes, total chlorophyll (Chl) accumulation, and elevated levels of hormones including indole-3-acetic acid (IAA), gibberellic acid (GA3), salicylic acid (SA)/methyl salicylate (MeSA), cytokinins (CK), abscisic acid (ABA), and jasmonic acid (JA). Weighted Gene Co-expression Network Analysis (WGCNA) identifies seven hub genes linked to photosynthesis and plant hormone regulation: MYB, KSC, SUAR, CESA POD, CESA, and SAUR. Collectively, shading signals induce P. bournei seedlings to elongate their stems and petioles, enhance photosynthetic enzyme activity, and accumulate specific hormones, with pertinent genes actively participating in light signal transduction. This research sheds light on the shading response mechanism of P. bournei, providing a robust theoretical framework for the breeding of shade-tolerant trees and the conservation of endangered species.

Transcriptome↗
PubMed2003

Sugar and hormone connections.

Sugars modulate many vital processes that are also controlled by hormones during plant growth and development. Characterization of sugar-signalling mutants in Arabidopsis has unravelled a complex signalling network that links sugar responses to two plant stress hormones--abscisic acid and ethylene--in opposite ways. Recent molecular analyses have revealed direct, extensive glucose control of abscisic acid biosynthesis and signalling genes that partially antagonizes ethylene signalling during seedling development under light. Glucose and abscisic acid promote growth at low concentrations but act synergistically to inhibit growth at high concentrations. The effects of sugar and osmotic stress on morphogenesis and gene expression are distinct. The plasticity of plant growth and development are exemplified by the complex interplay of sugar and hormone signalling.

Abscisic Acid↗
PubMed1995

A GCC element and a G-box motif participate in ethylene-induced expression of the PRB-1b gene.

The PRB-1b gene codes for a basic-type pathogenesis-related protein and is activated at the transcriptional level by the plant hormone ethylene. To identify cis-acting DNA elements essential for ethylene induction, deleted and mutant forms of the PRB-1b promoter, fused to the beta-glucuronidase (GUS) coding region, were introduced in transgenic tobacco plants. A 73 bp fragment (X1 region) of the PRB-1b promoter, located between positions -213 and -141, was sufficient to confer ethylene responsiveness to the reporter gene. The X1 region contains a TAAGAGCCGCC motif (GCC-box) well conserved in several ethylene-inducible genes. A substitution mutation in this sequence, in the context of a 213 bp PRB-1b promoter, completely abolished ethylene induction in transgenic tobacco, defining this conserved motif as part of a cis-acting element responsive to ethylene. Three other mutations in the X1 region caused a pronounced decrease in the PRB-1b promoter activity in transgenic plants, but did not affect ethylene inducibility. One of them, localized in a G-box like motif (CACGTG), disrupted the binding site for a nuclear factor, as observed in gel-shift analysis. Interestingly, the mobility of the complex formed on the G-box element was dependent on its phosphorylation state. These results suggest that a cis-acting element involved in the perception of the ethylene signal resides in a GCC motif and acts in concert with additional elements in the regulation of ethylene-induced PRB-1b expression.

Base Sequence↗
PubMed2006

S-Adenosyl-L-methionine: beyond the universal methyl group donor.

S-Adenosyl-l-methionine (AdoMet or SAM) is a substrate in numerous enzyme-catalyzed reactions. It not only provides methyl groups in many biological methylations, but also acts as the precursor in the biosynthesis of the polyamines spermidine and spermine, of the metal ion chelating compounds nicotianamine and phytosiderophores, and of the gaseous plant hormone ethylene. AdoMet is also the source of catalytic 5'-deoxyadenosyl radicals, produced as reaction intermediates by the superfamily of radical AdoMet enzymes. This review aims to summarize the present knowledge of catalytic roles of AdoMet in plant metabolism.

Azetidinecarboxylic Acid↗
PubMed2005

Characterization and expression analysis of a MADS box gene, HoMADS2, in Hyacinthus orientalis L.

A MADS box gene HoMADS2 was cloned from Hyacinthus orientalis L. in this study. Sequence comparison revealed that HoMADS2 was highly homologous to the class B MADS box genes. Furthermore, phylogenetic analysis showed that HoMADS2 was closely related to PI gene family and this was also supported by the presence of specific diagnostic sites of PI homologs in K box domain and C terminal region,suggesting that HoMADS2 might be a PI-like gene. HoMADS2 mRNA was accumulated in all floral organs,different from the expression patterns of PI homologs in dicots. During in vitro flower development, HoMADS2 expression was constitutively expressed and not affected by the presence of cytokinin and auxin in the regenerated flowers. Our results indicated that the expression of HoMADS2 is different from those of both HAG1 and HoMADS1 in responding to plant hormones during in vitro flower development.

Gene Expression Regulation, Plant↗
PubMed1996

Rat natriuretic peptide binds specifically to plant membranes and induces stomatal opening.

Stomatal aperture changes modulate the rate of transpiration and gas exchange in plants. High cellular turgor of the guard cell pair due to water and solute influx leads to stomatal opening, whereas closing is caused by turgor reduction due to water and solute efflux. This process is controlled by plant hormones. We demonstrate that a vertebrate peptide hormone, the rat atrial natriuretic peptide (rANP), induces stomatal opening in Tradescantia sp. in a concentration dependent manner and provide evidence that rANP affects the amiloride sensitive Na+/H- channel. Furthermore, rANP was found to bind specifically to plant membranes isolated from leaf tissue. We propose that a plant natriuretic peptide (NP) analogue is part of a multifactorial control system that regulates transpiration and solute movements in plants.

Amiloride↗
PubMed2006

SHR5: a novel plant receptor kinase involved in plant-N2-fixing endophytic bacteria association.

Endophytic nitrogen-fixing bacteria have been isolated from graminaceous plants such as maize, rice, and sugarcane. They are thought to promote plant growth, not only by fixing nitrogen, but also by the production of plant hormones. The molecular mechanisms involved in this interaction are not yet clear. In this work, the identification of a receptor-like kinase (RLK), named SHR5, which may participate in signal transduction involved in the establishment of plant-endophytic bacteria interaction is described for the first time. SHR5 seems to be part of a novel subclass of RLKs present in a wide range of plant species. The expression of this gene is down-regulated in sugarcane plants associated exclusively with beneficial endophytic bacteria and is not a general response caused by micro-organisms or abiotic stress. In addition, more successful sugarcane-endophytic bacteria associations have a more pronounced decrease in SHR5 expression, suggesting that SHR5 mRNA levels in plant cells are inversely related to the efficiency of the association.

Actinobacteria↗
PubMed2004

Comparative studies on the type-B response regulators revealing their distinctive properties in the His-to-Asp phosphorelay signal transduction of Arabidopsis thaliana.

In Arabidopsis thaliana, a Histidine-to-Aspartate (His-->Asp) phosphorelay is involved in the signal transduction for propagation of certain stimuli, such as plant hormones. Through the phosphorelay, the type-B phospho-accepting response regulator (ARR) family members serve as DNA-binding transcriptional regulators, whose activities are most likely regulated by phosphorylation/dephosphorylation. Based on the fact that this higher plant has 11 type-B ARR family genes, we clarified the expression profiles for all of their transcripts in plants. We constructed and characterized a series of transgenic lines, each carrying a given ARR-promoter::GUS transgene. Transcripts of some type-B ARR family genes were detected more or less ubiquitously in many organs tested, while others were expressed predominantly in reproductive organs. These ARR family members were phylogenetically classified into three sub-families, the largest of which includes the well-characterized ARR1, ARR2, and ARR11. Comparative studies were conducted focusing on ARR20 and ARR21, each of which is a representative member of an uncharacterized minor sub-family. A set of transgenic lines was constructed, in each of which a C-terminal DNA-binding domain lacking the N-terminal phospho-accepting receiver of a given ARR was aberrantly overexpressed. These resulting transgenic lines, including ARR14-C-ox, ARR20-C-ox, and ARR21-C-ox, showed characteristic anomalies during development. These results are discussed with special reference to the His-->Asp phosphorelay signal transduction in A. thaliana.

Arabidopsis↗
PubMed1997

Studies on biosynthesis of brassinosteroids.

Biosynthesis of steroidal plant hormones, brassinosteroids, was studied using the cell culture system of Catharanthus roseus. Feeding labeled compounds of possible intermediates to the cultured cells, followed by analyzing the metabolites by gas chromatography-mass spectrometry disclosed the pathways from a plant sterol, campesterol, to brassinolide. There are two pathways, named the early C6-oxidation pathway and late C6-oxidation pathway, both of which would be operating in a wide variety of plants. Recent findings of brassinosteroid-deficient mutants of Arabidopsis and the garden pea by several groups, and the possible blocked steps of the mutants in the biosynthetic pathways are also introduced.

Brassinosteroids↗
PubMed2007

Arabidopsis thaliana GH3.9 influences primary root growth.

Auxins regulate a complex signal transduction network to direct plant development. Auxin-responsive genes fit into three major classes: the so-called auxin/indole-3-acetic acid (Aux/IAA), the GH3, and the small auxin-up RNA (SAUR) gene families. The 20-member Arabidopsis thaliana GH3 gene family has been subdivided into three groups. In vitro studies have shown that most Group II members function as IAA-amido synthetases to conjugate amino acids to the plant hormone auxin. Here we report the role of a previously uncharacterized GH3 gene family member, GH3.9, in root growth. Unlike most other Group II family members, GH3.9 expression was repressed by low concentrations of exogenous IAA in seedlings. Transgenic plants harboring a GH3.9 promoter::reporter gene construct indicate that GH3.9 is expressed in the root-hypocotyl junction, leaves and the shoot apical meristem of young seedlings, in mature embryos, and in the root vascular tissue. Expression was also observed in lateral root tips when seedlings were treated with exogenous IAA. Inverse PCR was used to identify an activation tagged T-DNA insertion in chromosome 2 near the 5'UTR region of At2g47750 (GH3.9). Plants homozygous for the T-DNA insertion (gh3.9-1 mutants) had reduced GH3.9 expression, no obvious effects on apical dominance or leaf morphology, greater primary root length, and increased sensitivity to indole-3-acetic acid (IAA)-mediated root growth inhibition. Additional T-DNA insertion alleles and transgenic plants with reduced GH3.9 transcript levels due to RNA-interference (RNAi) also showed these same phenotypes. Our results provide new information on the function of GH3.9 in roots where it is likely to control auxin activity through amino acid conjugation.

Amino Acids↗
PubMed2003

Multiherbicide tolerance conferred by AtPgp1 and apyrase overexpression in Arabidopsis thaliana.

Herbicide resistance is an important trait often introduced into crop plants. Mechanisms of resistance can involve a mutant target protein that is unaffected by the herbicide, or metabolic detoxification or degradation of the herbicide. Recently, we showed that overexpression in Arabidopsis thaliana of either psNTP9, the garden pea apyrase gene, or AtPgp1, the A. thaliana homolog of the plant multidrug resistance (MDR) gene, enabled A. thaliana to germinate on the toxin cycloheximide and to grow better on toxic levels of the plant hormone N6-[2-isopentyl]adenine (2iP). Here we report that overexpression of either MDR or apyrase proteins resulted in increased resistance to herbicides from different chemical classes. Apyrase inhibition by small molecule inhibitors reversed this resistance. Treatment of untransformed plants with an apyrase inhibitor increased their sensitivity to the same herbicides. These results indicate that the genes may be involved in a resistance mechanism relating to decreased retention or increased active efflux of herbicide from the plant cell.

ATP Binding Cassette Transporter, Subfamily B↗
PubMed2000

The tomato ethylene receptors NR and LeETR4 are negative regulators of ethylene response and exhibit functional compensation within a multigene family.

The plant hormone ethylene is involved in many developmental processes, including fruit ripening, abscission, senescence, and leaf epinasty. Tomato contains a family of ethylene receptors, designated LeETR1, LeETR2, NR, LeETR4, and LeETR5, with homology to the Arabidopsis ETR1 ethylene receptor. Transgenic plants with reduced LeETR4 gene expression display multiple symptoms of extreme ethylene sensitivity, including severe epinasty, enhanced flower senescence, and accelerated fruit ripening. Therefore, LeETR4 is a negative regulator of ethylene responses. Reduced expression of this single gene affects multiple developmental processes in tomato, whereas in Arabidopsis multiple ethylene receptors must be inactivated to increase ethylene response. Transgenic lines with reduced NR mRNA levels exhibit normal ethylene sensitivity but elevated levels of LeETR4 mRNA, indicating a functional compensation of LeETR4 for reduced NR expression. Overexpression of NR in lines with lowered LeETR4 gene expression eliminates the ethylene-sensitive phenotype, indicating that despite marked differences in structure these ethylene receptors are functionally redundant.

Arabidopsis↗
PubMed2004

The Arabidopsis transcription factor HY5 integrates light and hormone signaling pathways.

The role of the Arabidopsis transcription factor LONG HYPOCOTYL 5 (HY5) in promoting photomorphogenic development has been extensively characterized. Although the current model for HY5 action largely explains its role in this process, it does not adequately address the root phenotype observed in hy5 mutants. In our search for common mechanisms underlying all hy5 traits, we found that they are partly the result of an altered balance of signaling through the plant hormones auxin and cytokinin. hy5 mutants are resistant to cytokinin application, and double mutant analyses indicate that a decrease in auxin signaling moderates hy5 phenotypes. Microarray analyses and semiquantitative RT-PCR indicate that two negative regulators of auxin signaling, AUXIN RESISTANT 2 (AXR2)/INDOLE ACETIC ACID 7 (IAA7) and SOLITARY ROOT (SLR)/IAA14, are underexpressed in hy5 mutants. The promoters of these genes contain a putative HY5 binding site, and in line with this observation, HY5 can bind to the promoter of AXR2 in vitro. Increased AXR2 expression in a hy5 background partially rescues the elongated hypocotyl phenotype. In summary, it appears that auxin signaling is elevated in hy5 mutants because HY5 promotes the expression of negative regulators of auxin signaling, thereby linking hormone and light signaling pathways.

Arabidopsis↗
PubMed2000

Phylogenetic analysis of the UDP-glycosyltransferase multigene family of Arabidopsis thaliana.

A class of UDP-glycosyltransferases (UGTs) defined by the presence of a C-terminal consensus sequence is found throughout the plant and animal kingdoms. Whereas mammalian enzymes use UDP-glucuronic acid, the plant enzymes typically use UDP-glucose in the transfer reactions. A diverse array of aglycones can be glucosylated by these UGTs. In plants, the aglycones include plant hormones, secondary metabolites involved in stress and defense responses, and xenobiotics such as herbicides. Glycosylation is known to regulate many properties of the aglycones such as their bioactivity, their solubility, and their transport properties within the cell and throughout the plant. As a means of providing a framework to start to understand the substrate specificities and structure-function relationships of plant UGTs, we have now applied a molecular phylogenetic analysis to the multigene family of 99 UGT sequences in Arabidopsis. We have determined the overall organization and evolutionary relationships among individual members with a surprisingly high degree of confidence. Through constructing a composite phylogenetic tree that also includes all of the additional plant UGTs with known catalytic activities, we can start to predict both the evolutionary history and substrate specificities of new sequences as they are identified. The tree already suggests that while the activities of some subgroups of the UGT family are highly conserved among different plant species, others subgroups shift substrate specificity with relative ease.

Arabidopsis↗
PubMed2003

The RUB/Nedd8 conjugation pathway is required for early development in Arabidopsis.

The related-to-ubiquitin (RUB) protein is post-translationally conjugated to the cullin subunit of the SCF (SKP1, Cullin, F-box) class of ubiquitin protein ligases. Although the precise biochemical function of RUB modification is unclear, studies indicate that the modification is important for SCF function. In Arabidopsis, RUB modification of CUL1 is required for normal function of SCF(TIR1), an E3 required for response to the plant hormone auxin. In this report we show that an Arabidopsis protein called RCE1 functions as a RUB-conjugating enzyme in vivo. A mutation in the RCE1 gene results in a phenotype like that of the axr1 mutant. Most strikingly, plants deficient in both RCE1 and AXR1 have an embryonic phenotype similar to mp and bdl mutants, previously shown to be deficient in auxin signaling. Based on these results, we suggest that the RUB-conjugation pathway is required for auxin-dependent pattern formation in the developing embryo. In addition, we show that RCE1 interacts directly with the RING protein RBX1 and is present in a stable complex with SCF. We propose that RBX1 functions as an E3 for RUB modification of CUL1.

Animals↗
PubMed2001

Combining genetics and cell biology to crack the code of plant cell calcium signaling.

Plant hormones, light receptors, pathogens, and abiotic signals trigger elevations in the cytosolic calcium concentration, which mediate physiological and developmental responses. Recent studies are reviewed here that reveal how specific genetic mutations impair or modify stimulus-induced calcium elevations in plant cells. These studies provide genetic evidence for the importance of calcium as a second messenger in plant signal transduction. A fundamental question arises: How can different stimuli use the same second messenger, calcium, to mediate different responses? Recent research and models are reviewed that suggest that several important mechanisms contribute to specificity in calcium signaling in plant cells. These mechanisms include (i) activation of different calcium channels in the plasma membrane and organellar membranes, (ii) stimulus-specific calcium oscillation parameters, (iii) cell type-specific responses, and (iv) intracellular localization of calcium gradients and calcium elevations in plant cells.

Arabidopsis↗
PubMed2006

Transcription factor families in Arabidopsis: major progress and outstanding issues for future research.

Transcription factors (TFs) are a group of proteins that control cellular processes by regulating the expression of downstream target genes. Recent progress has been made in the cloning and characterization of Arabidopsis TFs on the genome scale, especially on the cloning of open reading frames (ORFs), sequence analysis and the expression profiling of different TF families. Huge difference in numbers of subfamily members were found for Arabidopsis MYB, C2H2 (Zn), C3H-type 1 (Zn), C3H-type 2 (Zn) TFs by independent research groups, mainly because of differences in bioinformatic search stringency. However, the Arabidopsis and rice genomes contain very different numbers of TFs in the WRKY, NAC, bZIP, MADS, ALFIN-like, GRAS and C2C2 (Zn)-dof families, indicating a possible divergence of biological functions from dicots to monocots. TFs have also been found to play key roles in the biosynthesis and signaling of plant hormones, in cell growth and differentiation, and in photomorphogenesis.

Abscisic Acid↗
PubMed2006

Seed dormancy and the control of germination.

Seed dormancy is an innate seed property that defines the environmental conditions in which the seed is able to germinate. It is determined by genetics with a substantial environmental influence which is mediated, at least in part, by the plant hormones abscisic acid and gibberellins. Not only is the dormancy status influenced by the seed maturation environment, it is also continuously changing with time following shedding in a manner determined by the ambient environment. As dormancy is present throughout the higher plants in all major climatic regions, adaptation has resulted in divergent responses to the environment. Through this adaptation, germination is timed to avoid unfavourable weather for subsequent plant establishment and reproductive growth. In this review, we present an integrated view of the evolution, molecular genetics, physiology, biochemistry, ecology and modelling of seed dormancy mechanisms and their control of germination. We argue that adaptation has taken place on a theme rather than via fundamentally different paths and identify similarities underlying the extensive diversity in the dormancy response to the environment that controls germination.

Germination↗