Showing papers in "Plant Molecular Biology in 1994"
TL;DR: The newpPZP Agrobacterium binary vectors are versatile, relatively small, stable and fully sequenced, allowing their use inAgrobacteria strains with different drug resistance markers.
Abstract: The newpPZP Agrobacterium binary vectors are versatile, relatively small, stable and are fully sequenced. The vectors utilize the pTiT37 T-DNA border regions, the pBR322bom site for mobilization fromEscherichia coli toAgrobacterium, and the ColE1 and pVS1 plasmid origins for replication inE. coli and inAgrobacterium, respectively. Bacterial marker genes in the vectors confer resistance to chloramphenicol (pPZP100 series) or spectinomycin (pPZP200 series), allowing their use inAgrobacterium strains with different drug resistance markers. Plant marker genes in the binary vectors confer resistance to kanamycin or to gentamycin, and are adjacent to the left border (LB) of the transferred region. A lacZ α-peptide, with the pUC18 multiple cloning site (MCS), lies between the plant marker gene and the right border (RB). Since the RB is transferred first, drug resistance is obtained only if the passenger gene is present in the transgenic plants.
1,589 citations
TL;DR: Histochemical staining experiments and gene fusion experiments indicated that the 5′ region of cor15a between nucleotides −305 and +78 (relative to the start of transcription) contains a cis-acting element(s) that can impart cold-regulated gene expression.
Abstract: Previous nuclear run-on experiments indicated that the cor15a (cold-regulated) gene of Arabidopsis thaliana L. (Heyn) has a cold-inducible promoter (Hajela et al., Plant Physiol 93: 1246-1252, 1990). The data presented here indicate that the 5' region of cor15a between nucleotides -305 and +78 (relative to the start of transcription) contains a cis-acting element(s) that can impart cold-regulated gene expression. Histochemical staining experiments indicated that the cor15a promoter is inactive, or very weakly active, in most of the tissues and organs of plants grown at normal temperature and that it becomes activated throughout most of the plant in response to low temperature. Notable exceptions to this general pattern include constitutive activity of the promoter in anthers of control grown plants and apparent inactivity of the promoter in the roots and ovaries of cold-treated plants. Histochemical staining experiments also indicated that low temperature regulation of cor15a does not involve the synthesis of a regulatory molecule that can spread throughout the plant and induce cor gene expression at normal growth temperature. Finally, gene fusion experiments indicated that the 5' region of cor15a between nucleotides -305 and +78, in addition to imparting cold-regulated gene expression, can impart ABA- and drought-regulated gene expression.
810 citations
TL;DR: Two novel Arabidopsis phytochrome genes,PHYD andPHYE, are described and evidence is presented that, together with the previously describedPHYA, PHYB andPHYC genes, the primary structures of the complete phy tochrome family of this plant are now known.
Abstract: Two novel Arabidopsis phytochrome genes, PHYD and PHYE, are described and evidence is presented that, together with the previously described PHYA, PHYB and PHYC genes, the primary structures of the complete phytochrome family of this plant are now known The PHYD- and PHYE-encoded proteins are of similar size to the other phytochrome apoproteins and show sequence similarity along their entire lengths Hence, red/far-red light sensing in higher plants is mediated by a diverse but structurally conserved group of soluble photoreceptors The proteins encoded by the PHYD and PHYE genes are more closely related to phytochrome B than to phytochromes A or C, indicating that the evolution of the PHY gene family in Arabidopsis includes an expansion of a PHYB-related subgroup The PHYB and PHYD phytochromes show greater than 80% amino acid sequence identity but the phenotypes of phyB null mutants demonstrate that these receptor forms are not functionally redundant The five PHY mRNAs are, in general, expressed constitutively under varying light conditions, in different plant organs, and over the life cycle of the plant These observations provide the first description of the structure and expression of a complete phytochrome family in a higher plant
653 citations
TL;DR: Today, such plant-derived medicines as quinine, digitalis, opiates and morphine are widely used, while new natural chemicals such as the putative anti-cancer drug taxol from yew tree bark are being characterized and developed.
Abstract: Plants are one of the world’s richest sources of natural medicines. The use of plants and plant extracts for healing dates back to earliest recorded history. Today, such plant-derived medicines as quinine, digitalis, opiates and morphine are widely used, while new natural chemicals such as the putative anti-cancer drug taxol from yew tree bark are being characterized and developed.
629 citations
TL;DR: The analysis of the genomic organization and expression of these genes in response to light shows that PAL and StSy genes belong to large multigene families, while the others are present in one to four copies per haploid genome.
Abstract: Genes involved in flavonoid and stilbene biosynthesis were isolated from grape (Vitis vinifera L.). Clones coding for phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS), chalcone isomerase (CHI), flavanone 3-hydroxylase (F3H), dihydroflavonol 4-reductase (DFR), leucoanthocyanidin dioxygenase (LDOX) and UDP glucose:flavonoid 3-O-glucosyl transferase (UFGT), were isolated by screening a cDNA library, obtained from mRNA from seedlings grown in light for 48 h using snapdragon (Antirrhinum majus) and maize heterologous probes. A cDNA clone coding for stilbene synthase (StSy) was isolated by probing the library with a specific oligonucleotide. These clones were sequenced and when the putative products were compared to the published amino acid sequence for corresponding enzymes, the percentages of similarity ranged from 65% (UFGT) to 90% (CHS and PAL). The analysis of the genomic organization and expression of these genes in response to light shows that PAL and StSy genes belong to large multigene families, while the others are present in one to four copies per haploid genome. The steady-state level of mRNAs encoded by the flavonoid biosynthetic genes as determined in young seedlings is coordinately induced by light, except for PAL and StSy, which appear to be constitutively expressed.
475 citations
TL;DR: Prospects for rational engineering in this family include important members of plant origin, such as α-amylase, starch branching and debranching enzymes, and amylomaltase.
Abstract: Most starch hydrolases and related enzymes belong to the alpha-amylase family which contains a characteristic catalytic (beta/alpha)8-barrel domain. Currently known primary structures that have sequence similarities represent 18 different specificities, including starch branching enzyme. Crystal structures have been reported in three of these enzyme classes: the alpha-amylases, the cyclodextrin glucanotransferases, and the oligo-1,6-glucosidases. Throughout the alpha-amylase family, only eight amino acid residues are invariant, seven at the active site and a glycine in a short turn. However, comparison of three-dimensional models with a multiple sequence alignment suggests that the diversity in specificity arises by variation in substrate binding at the beta-->alpha loops. Designed mutations thus have enhanced transferase activity and altered the oligosaccharide product patterns of alpha-amylases, changed the distribution of alpha-, beta- and gamma-cyclodextrin production by cyclodextrin glucanotransferases, and shifted the relative alpha-1,4:alpha-1,6 dual-bond specificity of neopullulanase. Barley alpha-amylase isozyme hybrids and Bacillus alpha-amylases demonstrate the impact of a small domain B protruding from the (beta/alpha)8-scaffold on the function and stability. Prospects for rational engineering in this family include important members of plant origin, such as alpha-amylase, starch branching and debranching enzymes, and amylomaltase.
438 citations
TL;DR: This research focused on the synthesis and accumulation of antimicrobial phytoalexins in response to microbial attack, and the active components in these extracts are commonly referred to as ‘elicitors’.
Abstract: Oligosaccharins are complex carbohydrates that can function in plants as molecular signals that regulate growth, development, and survival in the environment [3]. Studies of plant-microorganism interactions yielded the first evidence that oligosaccharins could serve as biological signals. Much of this research focused on the synthesis and accumulation of antimicrobial phytoalexins in response to microbial attack. Phytoalexin synthesis and accumulation are observed not only after microbial infection, but also after treatment of plant tissue with cell-free extracts of microbial origin. The active components in these extracts are commonly referred to as ‘elicitors’. The term ‘elicitor’ was originally used to refer to molecules and other stimuli that induce the synthesis and accumulation of phytoalexins in plant cells [130], but is now commonly used for molecules that stimulate any plant defense mechanism [68, 70, 71, 104].
370 citations
TL;DR: The identity of puroindolines to wheat starch-granule associated proteins is discussed as well as the potential role of pocindoline in the plant defence mechanism.
Abstract: From a mid-maturation seed cDNA library we have isolated cDNA clones encoding two Triticum aestivum puroindolines. Puroindoline-a and puroindoline-b, which are 55% similar, are basic, cystine-rich and tryptophan-rich proteins. Puroindolines are synthezised as preproproteins which include N- and C-terminal propeptides which could be involved in their vacuolar localization. The mature proteins have a molecular mass of 13 kDa and a calculated isoelectric point greater than 10. A notable feature of the primary structure of puroindolines is the presence of a tryptophan-rich domain which also contains basic residues. A similar tryptophan-rich domain was found within an oat seed protein and a mammalian antimicrobial peptide. The ten cysteine residues of puroindolines are organized in a cysteine skeleton which shows similarity to the cysteine skeleton of other wheat seed cystine-rich proteins. Northern blot analysis showed that puroindoline genes are specifically expressed in T. aestivum developing seeds. No puroindoline transcripts as well as no related genes were detected in Triticum durum. The identity of puroindolines to wheat starch-granule associated proteins is discussed as well as the potential role of puroindolines in the plant defence mechanism.
361 citations
TL;DR: Interestingly, ethylene has also been shown to have opposite effects in some plants; for instance, it inhibits stem elongation in most dicots, whereas in some aquatic dicot and rice, it stimulates growth.
Abstract: Ethylene is one of the simplest organic molecules with biological activity. At concentrations as low as 0.1 ppm in air, it has been shown to have dramatic effects on plant growth and development [1]. Neljubov [78] was the first to show that ethylene has three major effects in etiolated pea seedlings called the triple response: (1) diageotropic growth, (2) thickening of stem and inhibition of stem elongation, and (3) exaggeration of apical hook curvature. Since then, numerous ethylene effects have been described in light-grown plants such as sex determination in curcurbits, fruit ripening in climacteric fruits, epinastic curvature, flower senescence, and root initiation [1]. Interestingly, ethylene has also been shown to have opposite effects in some plants; for instance, it inhibits stem elongation in most dicots, whereas in some aquatic dicots and rice, it stimulates growth [1, 45, 72].
328 citations
TL;DR: The characterization of deficient mutants has clarified the ABA biosynthetic pathway in higher plants, and characterization of mutants defective in ABA responsiveness, and molecular cloning of the corresponding loci has proven a powerful approach to dissect the molecular nature of ABA signalling cascades.
Abstract: Abscisic acid (ABA) participates in the control of diverse physiological processes. The characterization of deficient mutants has clarified the ABA biosynthetic pathway in higher plants. Deficient mutants also lead to a revaluation of the extent of ABA action during seed development and in the response of vegetative tissues to environmental stress. Although ABA receptor(s) have not yet been identified, considerable progress has been recently made in the characterization of more downstream elements of the ABA regulatory network. ABA controls stomatal aperture by rapidly regulating identified ion transporters in guard cells, and the details of the underlying signalling pathways start to emerge. ABA actions in other cell types involve modifications of gene expression. The promoter analysis of ABA-responsive genes has revealed a diversity of cis-acting elements and a few associated trans-acting factors have been isolated. Finally, characterization of mutants defective in ABA responsiveness, and molecular cloning of the corresponding loci, has proven to be a powerful approach to dissect the molecular nature of ABA signalling cascades.
320 citations
TL;DR: As the understanding of GA-regulated events in aleurone cells has advanced through molecular and cell biology approaches, other GA-responsive plant tissues have also proved to be tractible for studying GA-action.
Abstract: Gibberellins (GAs) are a class of plant hormones that exert profound and diverse effects on plant growth and development. The chemistry and metabolism of GAs have been studied for several decades and this has led to a detailed understanding of the pathways involved in their biosynthesis and catabolism. Attempts to understand the perception and mechanism of action of GAs have been based heavily on studies with the cereal aleurone as a model system and have drawn extensively on parallels with the molecular mechanism of action of mammalian steroid hormones. During the past few years, the established view of GA-perception has been challenged and new techniques for identifying GA receptors have been developed. As our understanding of GA-regulated events in aleurone cells has advanced through molecular and cell biology approaches, other GA-responsive plant tissues have also proved to be tractible for studying GA-action.
TL;DR: Results suggest that this 20 nucleotide sequence is essential for the nos promoter to function and substitution of the nos element with the ocs or 35S as-1 which contain similar hexamer motifs restored not only promoter activity but also responses to wounding, auxin, methyl jasmonate, and salicylic acid.
Abstract: The nopaline synthase (nos) promoter is expressed in a wide range of plant cell types and regulated by various developmental and environmental factors. The nos upstream control region essential for this regulation was studied by means of synthetic oligomers using transient and stable transformation systems. Insertion of a 20 nucleotide sequence containing two hexamer motifs and a spacer region into deletion mutants lacking the upstream control region was essential for promoter activity. Mutation of one or more nucleotides of either hexamer sequence significantly altered the strength of expression of the nos promoter. Point mutations within the spacer region also strongly influenced promoter strength. Insertion of multiple copies of the 20 nucleotide sequence into the nonfunctional deletion mutants proportionally increased the promoter activity. These results suggest that this twenty nucleotide sequence is essential for the nos promoter to function. Substitution of the nos element with the ocs or 35S as-1 which contain similar hexamer motifs restored not only promoter activity but also responses to wounding, auxin, methyl jasmonate, and salicylic acid.
TL;DR: Dehydration stress strongly induced the expression of genes for the three ERDs, while application of ABA did not significantly affect the ERD gene expression, suggesting that these HSP cognates are preferentially responsive to dehydration stress in A. thaliana.
Abstract: InArabidopsis thaliana L., accumulation of abscisic acid (ABA) began to increase 2 h after plants had been subjected to dehydration stress and reached maximum levels after 10h. Differential hybridization was used to isolate 26Arabidopsis cDNAs with gene expression induced by a 1 h dehydration treatment. The cDNA clones were classified into 16 groups based on Southern blot hybridization, and named ERD (early-responsive todehydration) clones. Partial sequencing of the cDNA clones revealed that three ERDs were identical to those of HSP cognates (Athsp70-1, Athsp81-2, and ubiquitin extension protein). Dehydration stress strongly induced the expression of genes for the three ERDs, while application of ABA, which is known to act as a signal transmitter in dehydration-stressed plants, did not significantly affect the ERD gene expression. This result suggests that these HSP cognates are preferentially responsive to dehydration stress inA. thaliana, and that signaling pathways for the expression of these genes under conditions of dehydration stress are not mainly mediated by ABA. We also discuss the possible functions of these three ERD gene products against dehydration stress.
TL;DR: Their in vitro toxicity to plant pathogenic bacteria and fungi could reflect a direct role in plant defence, although, in view of the many divergent activities displayed by thionins both in vitro and in vivo, a biological role other than inhibition of microbial growth is equally plausible.
Abstract: Thionins are low-molecular-weight proteins (M
r ca. 5000) occurring in seeds, stems, roots and leaves of a number of plant species. The different members of this family of plant proteins show both sequence and structural homology, and are toxic to bacteria, fungi, yeasts and various naked cells in vitro. Toxicity requires an electrostatic interaction of the positively charged thionin with the negatively charged phospholipids making up the membrane, followed by either pore formation or a specific interaction with a certain lipid domain. This domain might be composed of phosphoinositides, which mediate transduction of environmental signals in eukaryotes. Their in vitro toxicity to plant pathogenic bacteria and fungi could reflect a direct role in plant defence, although, in view of the many divergent activities displayed by thionins both in vitro and in vivo, a biological role other than inhibition of microbial growth is equally plausible.
TL;DR: The diversity among plant RLKs, reflected in their structural and functional properties, has opened up a broad new area of investigation into cellular signalling in plants with far-reaching implications for the mechanisms by which plant cells perceive and respond to extracellular signals.
Abstract: Cell surface receptors located in the plasma membrane have a prominent role in the initiation of cellular signalling. Recent evidence strongly suggests that plant cells carry cell surface receptors with intrinsic protein kinase activity. The plant receptor-like protein kinases (RLKs) are structurally related to the polypeptide growth factor receptors of animals which consist of a large extracytoplasmic domain, a single membrane spanning segment and a cytoplasmic domain of the protein kinase gene family. Most of the animal growth factor receptor protein kinases are tyrosine kinases; however, the plant RLKs all appear to be serine/threonine protein kinases. Based on structural similarities in their extracellular domains the RLKs fall into three categories: the S-domain class, related to the self-incompatibility locus glycoproteins of Brassica; the leucine-rich repeat class, containing a tandemly repeated motif that has been found in numerous proteins from a variety of eukaryotes; and a third class that has epidermal growth factorlike repeats. Distinct members of these putative receptors have been found in both monocotyledonous plants such as maize and in members of the dicotyledonous Brassicaceae. The diversity among plant RLKs, reflected in their structural and functional properties, has opened up a broad new area of investigation into cellular signalling in plants with far-reaching implications for the mechanisms by which plant cells perceive and respond to extracellular signals.
TL;DR: A DNA typing system using sequence-tagged microsatellite site markers as a means of differentiating cultivars of grapevine demonstrated that cultivars that are difficult to differentiate phenotypically using ampelographic techniques can be distinguished by DNA typing.
Abstract: With established ampelographic techniques for grapevine identification it is often difficult to achieve a satisfactory, objective result. We have developed a DNA typing system using sequence-tagged microsatellite site markers as a means of differentiating cultivars of grapevine. A semi-automated analysis procedure was linked to an electronic database and found to be an objective and reliable system for cultivar identification using this simple marker type. The accumulated DNA typing data from over eighty cultivars demonstrated that cultivars that are difficult to differentiate phenotypically using ampelographic techniques can be distinguished by DNA typing. Parentage analysis uncovered errors in parent assignment of cultivar identification in specific cases. The electronic database has a conservative format to take into account the occurrence of null alleles and the possibility of missed alleles. Computer-assisted comparisons of cultivars in the database can be performed and various approaches for estimating the match probability that two unrelated cultivars have the same genotype simply due to chance are discused. We suggest that further development of the database through international co-operation using standardised sequence-tagged site markers offers the possibility of achieving a universal grapevine identification system.
TL;DR: The demonstration of a gene from a monocotyledon with close sequence homology to the known non-legume plant haemoglobins fills a major gap in the known distributed haemoglobin genes in the plant kingdom.
Abstract: Legumes, and a very few non-legume plant species, are known to possess functioning haemoglobin genes. We describe here the characterization of a haemoglobin cDNA isolated from barley. The deduced amino acid sequence shows 71% amino acid identity with a non-legume haemoglobin gene, a further 16% of the residues being conservative replacements. The barley cDNA also hybridizes to genomic sequences in rye, maize and wheat. The demonstration of a gene from a monocotyledon with close sequence homology to the known non-legume plant haemoglobins fills a major gap in the known distribution of haemoglobin genes in the plant kingdom. The expression of the gene is induced in isolated barley aleurone layers exposed to anaerobic conditions, and the roots of flooding-stressed barley plants. The expression of the RNA under anoxic conditions is similar to that of a known anaerobic response gene, alcohol dehydrogenase. Our results suggest that the increased expression of haemoglobin RNA is an integral part of the normal anaerobic response in barley. The findings are discussed in the light of current theories of haemoglobin function and evolution.
TL;DR: The role of guanine nucleotide-binding proteins (G proteins) in the regulation of cell division and differentiation has been investigated extensively in animal and microbial organisms, and they are divided into the heterotrimeric and the small (monomeric) classes as discussed by the authors.
Abstract: Regulatory guanine nucleotide-binding proteins (G proteins) have been studied extensively in animal and microbial organisms, and they are divided into the heterotrimeric and the small (monomeric) classes. Heterotrimeric G proteins are known to mediate signal responses in a variety of pathways in animals and simple eukaryotes, whiole small G proteins perform diverse functions including signal transduction, secretion, and regulation of cytoskeleton. In recent years, biochemical analyses have produced a large amount of information on the presence and possible functions of G proteins in plants. Further, molecular cloning has clearly demonstrated that plants have both heterotrimeric and small G proteins. Although the functions of the plant heterotrimeric G proteins are yet to be determined, expression analysis of an Arabidopsis Gα protein suggests that it may be involved in the regulation of cell division and differentiation. In contrast to the very few genes cloned thus far that encode heterotrimeric G proteins in plants, a large number of small G proteins have been identified by molecular cloning from various plants. In addition, several plant small G proteins have been shown to be functional homologues of their counterparts in animals and yeasts. Future studies using a number of approaches are likely to yield insights into the role plant G proteins play.
TL;DR: Regulation of the level of bi-OMT expression by an antisense mechanism could be a useful tool for genetically engineering plants with modified lignin without altering normal growth and development.
Abstract: An aspen lignin-specific O-methyltransferase (bi-OMT; S-adenosyl-L-methionine: caffeic acid/5-hydroxyferulic acid 3/5-O-methyltransferase, EC 2.1.1.68) antisense sequence in the form of a synthetic gene containing the cauliflower mosaic virus 35S gene sequences for enhancer elements, promoter and terminator was stably integrated into the tobacco genome and inherited in transgenic plants with a normal phenotype. Leaves and stems of the transgenes expressed the antisense RNA and the endogenous tobacco bi-OMT mRNA was suppressed in the stems. Bi-OMT activity of stems was decreased by an average of 29% in the four transgenic plants analyzed. Chemical analysis of woody tissue of stems for lignin building units indicated a reduced content of syringyl units in most of the transgenic plants, which corresponds well with the reduced activity of bi-OMT. Transgenic plants with a suppressed level of syringyl units and a level of guaiacyl units similar to control plants were presumed to have lignins of distinctly different structure than control plants. We concluded that regulation of the level of bi-OMT expression by an antisense mechanism could be a useful tool for genetically engineering plants with modified lignin without altering normal growth and development.
TL;DR: Two new dhn/lea/rab (dehydrin, late embryogenesis-abundant, responsive to ABA)-related genes from Arabidopsis thaliana are characterized and are strongly induced in plants exposed to low temperature (4 °C) and designated lti45 and lti30 (low temperature-induced).
Abstract: We have characterized cDNAs for two new dhn/lea/rab (dehydrin, late embryogenesis-abundant, responsive to ABA)-related genes from Arabidopsis thaliana. The two genes were strongly induced in plants exposed to low temperature (4 °C) and were accordingly designated lti45 and lti30 (low temperature-induced). The lti45 gene product contains the conserved serine stretch and three lysine-rich repeats characteristic of DHN/LEA/RAB proteins and is very similar to another low temperature-responsive protein of A. thaliana, COR47 [17]. Both proteins have the same repeat structure and an overall amino acid identity of 64%. This structural similarity of the proteins and the tandem array of the genes suggest that this gene pair arose through a duplication. The other polypeptide, LTI30, consists of several lysine-rich repeats, a structure found in CAP85, a low temperature-and water stress-responsive protein in spinach [41] and similar proteins found in wheat [20]. The expression pattern of the five dhn/lea/rab-related genes (cor47, dhnX, lti30, lti45 and rab18) identified so far in A. thaliana, was characterized in plants exposed to low temperature, drought and abscisic acid (ABA). Expression of both lti30 and lti45 was mainly responsive to low temperature similar to cor47. The lti45 and lti30 genes show only a weak response to ABA in contrast to cor47, which is moderately induced by this hormone. The three genes were also induced in severely water-stressed plants although the expression of lti30 and lti45 was rather low. In contrast to these mainly low temperature-induced genes, the expression of rab18 was strongly induced both in water-stressed and ABA-treated plants but was only slightly responsive to cold. The dhnX gene showed a very different expression pattern. It was not induced with any of the treatments tested but exhibited a significant constitutive expression. The low-temperature induction of the genes in the first group, lti30 and lti45, is ABA-independent, deduced from experiments with the ABA-deficient (aba-1) and ABA-insensitive (abi1) mutants of A. thaliana, whereas the induction of rab18 is ABA-mediated. The expression of dhnX was not significantly affected in the ABA mutants.
TL;DR: Transgene expression was typically, but not always, predictable in progeny plants-transgene silencing, as well as poor transgene transmission to progeny, was observed in some plant lines in which the parent plants had expressed the transgenes.
Abstract: Zea mays transformants produced by particle bombardment of embryogenic suspension culture cells of the genotype A188 × B73 and selected on kanamycin or bialaphos were characterized with respect to transgene integration, expression, and inheritance. Selection on bialaphos, mediated by thebar orpat genes, was more efficient than selection on kanamycin, mediated by thenptII gene. Most transformants contained multicopy, single locus, transgene insertion events. A transgene expression cassette was more likely to be rearranged if expression of that gene was not selected for during callus growth. Not all plants regenerated from calli representing single transformation events expressed the transgenes, and a non-selectable gene (uidA) was expressed in fewer plants than was the selectable transgene. Mendelian inheritance of transgenes consistent with transgene insertion at a single locus was observed for approximately two thirds of the transformants assessed. Transgene expression was typically, but not always, predictable in progeny plants-transgene silencing, as well as poor transgene transmission to progeny, was observed in some plant lines in which the parent plants had expressed the transgene.
TL;DR: It is shown that tomato plants contain at least four SAM isogenes, found to encode a S-adenosyl-L-methionine synthetase enzyme (AdoMet Synthetase), and a possible role for AdoMet synthetases in the adaptation to salt stress is discussed.
Abstract: NaCl stress causes the accumulation of several mRNAs in tomato seedlings. An upregulated cDNA clone, SAM1, was found to encode a S-adenosyl-L-methionine synthetase enzyme (AdoMet synthetase). Expression of the cDNA SAM1 in a yeast mutant lacking functional SAM genes resulted in high AdoMet synthetase activity and AdoMet accumulation. We show that tomato plants contain at least four SAM isogenes. Clones corresponding to isogenes SAM2 and SAM3 have also been isolated and sequenced. they encode predicted polypeptides 95% and 92% identical, respectively, to the SAM1-encoded AdoMet Synthetase. RNA hybridization analysis showed a differential response of SAM genes to salt and other stress treatments. SAM1 and SAM3 mRNAs accumulated in the root in response to NaCl, mannitol or ABA treatments. SAM1 mRNA accumulated also in leaf tissue. These increases of mRNA level were apparent as soon as 8 h after the initiation of the salt treatment and were maintained for at least 3 days. A possible role for AdoMet synthetases in the adaptation to salt stress is discussed.
TL;DR: The hypothesis that flavonoids protect DNA from UV-induced DNA damage is supported.
Abstract: In this study an in vitro run-off transcription assay was used to determine if flavonoids can prevent the accumulation of UV-B-induced DNA damage. Template plasmid DNA was irradiated with UV-B light, which resulted in a decreased capacity to support transcription. Purified flavonoids naringenin and rutin as well as flavonoid extracts from apple skin prevented the accumulation of DNA damage. The results support the hypothesis that flavonoids protect DNA from UV-induced DNA damage.
TL;DR: A highly conserved sequence was found in rRNA gene internal transcribed spacer 1 (ITS1) among flowering plant species, and may have a key function in the processing of r RNA gene transcripts.
Abstract: A highly conserved sequence was found in rRNA gene internal transcribed spacer 1 (ITS1) among flowering plant species. The sequence, GGCRY-(4 to 7 n)-GYGYCAAGGAA (where Y=C or T; R=G or A) is located in the central region of ITS1, and is present in published sequences from a wide range of flowering plants. The rest of ITS1 is highly variable in sequence. Therefore, the conserved motif within ITS1 may have a key function in the processing of rRNA gene transcripts. Furthermore, identification of such a conserved motif will help facilitate alignment of sequences for phylogenetic analysis.
TL;DR: Using plants genetically transformed with a cDNA for the calcium-sensitive luminescent protein, aequorin, touch and wind signals are shown to immediately increase cytosol calcium, and the specific role of calcium is considered.
Abstract: Calcium is a dynamic signalling molecule which acts to transduce numerous signals in plant tissues. The basis of calcium signalling is outlined and the necessity for measuring and imaging of calcium indicated. Using plants genetically transformed with a cDNA for the calcium-sensitive luminescent protein, aequorin, we have shown touch and wind signals to immediately increase cytosol calcium. Touch and wind signal plant cells mechanically, through tension and compression of appropiate cells. Many plant tissues and cells are very sensitive to mechanical stimulation and the obvious examples of climbing plants, insectivorous species as well as other less well-known examples are described. Touch sensing in these plants may be a simple evolutionary modification of sensitive mechanosensing system present in every plant. The possibility that gravitropism may be a specific adaptation of touch sensing is discussed. There is a growing appreciation that plant form may have a mechanical basis. A simple mechanical mechanism specifying spherical, cylindrical and flat-bladed structures is suggested. The limited morphological variety of plant tissues may also reflect mechanical specification. The article concludes with a discussion of the mechanisms of mechanical sensing, identifying integrin-like molecules as one important component, and considers the specific role of calcium.
TL;DR: Ever since Thimann proposed that auxin plays a role in nodule development, considerable effort has been expended to show whether phyto- hormones are involved, and it seems likely that they have a roleIn nodule de- velopment.
Abstract: Ever since Thimann [20] proposed that auxin plays a role in nodule development, considerable effort has been expended to show whether phyto- hormones are involved. Because the hormones are involved in other types of organogenesis, it seems likely that they have a role in nodule de- velopment. However, important questions remain unanswered:
TL;DR: The true nature of traumatic acid has been confusing due to the more recent discovery that this compound may have become modified during the extraction leading to its discovery, and many new facets of fatty acid signalling are emerging.
Abstract: Fatty acid signals in plants have a long history. A fatty acid derivative, traumatic acid, was identified as a cell division promoter in wounded bean mesocarp and was among the first ever biologically active molecules isolated directly from a plant tissue. A structure for this molecule was published in 1939 [20]. Indolyl-3-acetic acid (IAA), an auxin isolated from urine in 1934, was definitively isolated from plant tissues in 1942 by Haagen-Smit et al. [32]. Like the complex story of the discovery of the structures of auxins, the true nature of traumatic acid has been confusing due to the more recent discovery that this compound may have become modified during the extraction leading to its discovery [77]. With renewed interest in fatty acid signalling, some of the old literature is being revised and many new facets of fatty acid signalling are emerging.
TL;DR: Investigation of TAS14, an mRNA that is induced in tomato upon osmotic stress or abscisic acid (ABA) treatment and that shares expression and sequence characteristics with other dehydrin genes in different species, found that it accumulated in adventitious root primordia and associated to the provascular and vascular tissues in stems and leaves.
Abstract: We previously isolated and characterized TAS14, and mRNA that is induced in tomato upon osmotic stress or abscisic acid (ABA) treatment and that shares expression and sequence characteristics with other dehydrin genes in different species. Affinity-purified antibodies against TAS14 protein were used to study the expression of TAS14 protein, both in seedlings and mature plants, its tissue distribution and its subcellular localization. TAS14 protein was not detected in 4-day-old seedlings but accumulated after ABA, NaCl or mannitol treatments. In NaCl-treated seedlings, some protein was detectable after 6 h of treatment and reached maximal levels between 24 and 48 h. Concentrations ranging from 5 to 12.5 g/l NaCl induced the protein to similar levels. In salt-stressed mature plants, TAS14 was expressed abundantly and continuously in aerial parts, but only slightly and transiently in roots. Immunocytochemical analysis of salt-treated plants showed TAS14 accumulated in adventitious root primordia and associated to the provascular and vascular tissues in stems and leaves. Immunogold electron microscopy localized TAS14 protein both in the cytosol and in the nucleus, associated to the nucleolus and euchromatin. Since TAS14 is a phosphoprotein in vivo, the classes of protein kinases potentially responsible for its in vivo phosphorylation were tested in in vitro phosphorylation assays. TAS14 protein was phosphorylated in vitro by both casein kinase II and cAMP-dependent protein kinase.
TL;DR: The roots of tobacco plants transformed with these constructs produced antibodies that were able to bind antigen in an ELISA, and the construct with divergent promoters showed a better performance than the construct that binds to a fungal cutinase.
Abstract: To explore the feasibility of employing antibodies to obtain disease resistance against plant root pathogens, we have studied the expression of genes encoding antibodies in roots of transgenic plants. A model monoclonal antibody was used that binds to a fungal cutinase. Heavy and light chain cDNAs were amplified by PCR, fused to a signal sequence for secretion and cloned behind CaMV 35S and TR2′ promoters in a single T-DNA. The chimeric genes were cloned both in tandem and in a divergent orientation. The roots of tobacco plants transformed with these constructs produced antibodies that were able to bind antigen in an ELISA. Immunoblotting showed assembly to a full-size antibody. In addition, a F(ab′)2-like fragment was observed, which is probably formed by proteolytic processing. Both antibody species were properly targeted to the apoplast, but the full-size antibody was partially retained by the wall of suspension cells. The construct with divergent promoters showed a better performance than the construct with promoters in tandem. It directed the accumulation of functional antibodies to a maximum of 1.1% of total soluble protein, with half of the plants having levels higher than 0.35%. The high efficiency of this construct probably results from coordinated and balanced expression of light and heavy chain genes, as evidenced by RNA blot hybridization.
TL;DR: The results suggest that the OsMADS1 gene is involved in flower induction and that it may be used for genetic manipulation of certain plant species.
Abstract: Recent studies with dicot plants reveal that floral organ development is controlled by a group of regulatory factors containing the MADS domain. In this study, we have isolated and characterized a cDNA clone from rice, OsMADS1, which encodes a MADS-domain-containing protein. The OsMADS1 amino acid sequence shows 56.2% identity to AGL2 and 44,4% identity to AP1. The MADS box region was the most homologous to other MADS-domain-containing proteins. Northern blot analysis indicated that the rice MADS gene was preferentially expressed in floral organs. In situ localization studies showed that the transcript was uniformly present in young flower primordia and later became localized in palea, lemma, and ovary. Ectopic expression of OsMADS1 with the CaMV 35S promoter in transgenic tobacco plants dramatically alters development, resulting in short, bushy, early-flowering plants with reduced apical dominance. These results suggest that the OsMADS1 gene is involved in flower induction and that it may be used for genetic manipulation of certain plant species.