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At least 847 records · Page 47Linked to original sources
PubMed2002

Overexpression of a plasma membrane Na+/H+ antiporter gene improves salt tolerance in Arabidopsis thaliana.

High concentrations of Na+ in saline soils inhibit plant growth and reduce agricultural productivity. We report here that CaMV 35S promoter driven overexpression of the Arabidopsis thaliana SOS1 gene, which encodes a plasma membrane Na+/H+ antiporter, improves plant salt tolerance in A. thaliana. Transgenic plants showed substantial upregulation of SOS1 transcript levels upon NaCl treatment, suggesting post-transcriptional control of SOS1 transcript accumulation. In response to NaCl treatment, transgenic plants overexpressing SOS1 accumulated less Na+ in the xylem transpirational stream and in the shoot. Undifferentiated callus cultures regenerated from the transgenic plants were also more tolerant of salt stress, which was correlated with reduced Na+ content in the transgenic cells. These results show that improved salt tolerance could be achieved by limiting Na+ accumulation in plant cells.

Arabidopsis↗
PubMed1998

Identification of a family of zinc transporter genes from Arabidopsis that respond to zinc deficiency.

Millions of people worldwide suffer from nutritional imbalances of essential metals like zinc. These same metals, along with pollutants like cadmium and lead, contaminate soils at many sites around the world. In addition to posing a threat to human health, these metals can poison plants, livestock, and wildlife. Deciphering how metals are absorbed, transported, and incorporated as protein cofactors may help solve both of these problems. For example, edible plants could be engineered to serve as better dietary sources of metal nutrients, and other plant species could be tailored to remove metal ions from contaminated soils. We report here the cloning of the first zinc transporter genes from plants, the ZIP1, ZIP2, and ZIP3 genes of Arabidopsis thaliana. Expression in yeast of these closely related genes confers zinc uptake activities. In the plant, ZIP1 and ZIP3 are expressed in roots in response to zinc deficiency, suggesting that they transport zinc from the soil into the plant. Although expression of ZIP2 has not been detected, a fourth related Arabidopsis gene identified by genome sequencing, ZIP4, is induced in both shoots and roots of zinc-limited plants. Thus, ZIP4 may transport zinc intracellularly or between plant tissues. These ZIP proteins define a family of metal ion transporters that are found in plants, protozoa, fungi, invertebrates, and vertebrates, making it now possible to address questions of metal ion accumulation and homeostasis in diverse organisms.

Amino Acid Sequence↗
PubMed2003

Effect of hypobaric conditions on ethylene evolution and growth of lettuce and wheat.

Elevated levels of ethylene occur in enclosed crop production systems and in spaceflight environments, leading to adverse plant growth and sterility. There are engineering advantages in growing plants at hypobaric (reduced atmospheric pressure) conditions in biomass production for extraterrestrial base or spaceflight environments. Objectives of this research were to characterize the influence of hypobaria on growth and ethylene evolution of lettuce (Lactuca sativa) and wheat (Triticum aestivum). Plants were grown under variable total gas pressures [from 30 to 101 kPa (ambient)]. In one study, lettuce and wheat were direct seeded, germinated and grown in the same chambers for 28 d at 50 or 101 kPa. Hypobaria increased plant growth and did not alter germination rate. During a 10-day study, 28-day-old lettuce and 40-day-old wheat seedlings were transplanted together in the same low and ambient pressure chambers; ethylene accumulated in the chambers, but the rate of production by both lettuce and wheat was reduced more than 65% under 30 kPa compared with ambient pressure (101 kPa). Low O2 concentrations [partial pressure of O2 (pO2) = 6.2 kPa] inhibited ethylene production by lettuce under both low (30 kPa) and ambient pressure, whereas ethylene production by wheat was inhibited at low pressure but not low O2 concentration. There was a negative linear correlation between increasing ethylene concentration and decreasing chlorophyll content of lettuce and wheat. Lettuce had higher production of ethylene and showed greater sensitivity to ethylene than wheat. The hypobaric effect on reduced ethylene production was greater than that of just hypoxia (low oxygen).

Atmospheric Pressure↗
PubMed1993

Plant genetics: out with the old, in with the new?

Plant breeding represents an evolving technology based largely on genetic principles. Approximately one-half of the increased yields of major crop plants can be attributed to the genetic improvement of the crop. Although the breeding technology and undergirding science are sound, additional information on the biochemical pathways underlying agronomic and quality traits and their genetic control would allow new genetic technologies to be used more fully. Current developments in molecular biology, plant cell and tissue culture, genetic engineering, and use of molecular genetics will facilitate the selection of complex traits. Genetic improvement of plants in the future will be based on an integration of modern plant-breeding methods and the new genetic technologies. Thus, the new genetic approaches do not represent a replacement technology but will add to the arsenal of tools available for improving crops.

Agriculture↗
PubMed2001

Engineering variegated floral patterns in tobacco plants using the Arabidopsis transposable element Tag1.

Variegated flower phenotypes were generated using the Arabidopsis transposon Tag1 and the maize R regulatory gene. Tag1 was inserted between the CaMV 35S promoter and the maize R gene and transformed into tobacco plants. In half of the transgenic plants, variegated flower patterns were observed. Each line had a different pattern, with varying intensities with three lines showing only tiny sectors indicative of late excision and one showing large sectors indicative of earlier excision.

Arabidopsis↗
PubMed2005

A peroxiredoxin Q homolog from gentians is involved in both resistance against fungal disease and oxidative stress.

An antifungal protein (GtAFP1) showing antimicrobial activity against phytopathogenic fungi was purified from leaves of Gentiana triflora. The deduced amino acid sequence of the cDNA of the corresponding gene, GtAFP1, showed 94, 75, 72 and 63% amino acid identities with peroxiredoxin Q from Populus balsamifera x P. deltoides subsp. trichocarpa, Sedum lineare, Suaeda maritima and Arabidopsis thaliana, respectively. The GtAFP1 gene is suggested to be present in the genome in one to two copies and was expressed in the leaves, roots and stems. Expression of GtAFP1 was induced by treatment with salicylic acid, but not methyl jasmonate. Recombinant GtAFP1 protein showed not only antifungal activity but also thioredoxin-dependent peroxidase activity. Overexpression of GtAFP1 in tobacco plants improved tolerance not only against fungal diseases but also against oxidative stress. These results indicate that GtAFP1 might act as a disease and oxidative stress defensive gene in plants and could be useful for engineering stress-resistant plants.

Amino Acid Sequence↗
PubMed1996

Costs of resistance: a test using transgenic Arabidopsis thaliana.

Evolutionary biologists have long attributed polymorphisms in resistance status to fitness costs of resistance traits. Nevertheless, pleiotropic fitness costs of resistance have been notoriously difficult to detect. We have transformed Arabidopsis thaliana with a mutant acetolactate synthase gene that confers resistance to the herbicide, chlorsulfuron. Our experiment revealed a 34% reduction in the lifetime seed production of transgenic, herbicide resistant Arabidopsis thaliana relative to their susceptible null segregants. Our experimental design allows us to conclude that this fitness cost of resistance is caused by the pleiotropic effect of the introduced acetolactate synthase gene rather than other potential costs associated with the plasmid or mutational changes induced by plant transformation. In addition, we can attribute the cost of resistance to the presence of the resistance gene rather than an increase in gene dosages. The implications of these results for the risk assessment of transgenic crops are discussed.

Acetolactate Synthase↗
PubMed2005

Development of a virus-induced gene-silencing system for hexaploid wheat and its use in functional analysis of the Lr21-mediated leaf rust resistance pathway.

Virus-induced gene silencing (VIGS) is an important tool for the analysis of gene function in plants. In VIGS, viruses engineered to carry sequences derived from plant gene transcripts activate the host's sequence-specific RNA degradation system. This mechanism targets the RNAs of the viral genome for degradation, and as the virus contains transcribed plant sequence, homologous host mRNAs are also targeted for destruction. While routinely used in some dicots, no VIGS system was known for monocot plants until the recent report of silencing in barley (Hordeum vulgare) by barley stripe mosaic virus (BSMV). Here, we report development of protocols for use of BSMV to efficiently silence genes in hexaploid wheat (Triticum aestivum). The VIGS system was first optimized in studies silencing phytoene desaturase expression. Next, we used it to assay genes functioning in leaf rust resistance mediated by Lr21, which encodes a nucleotide binding site-leucine-rich repeat class resistance gene product. We demonstrated that infection with BSMV constructs carrying a 150-bp fragment of Lr21 caused conversion of incompatible interactions to compatible, whereas infection with a control construct or one that silences phytoene desaturase had no effect on resistance or susceptibility. Additionally, silencing the RAR1, SGT1, and HSP90 genes, known to be required in many but not all nucleotide binding site-leucine-rich repeat resistance pathways in diverse plant species, resulted in conversion to compatibility, indicating that these genes are essential in Lr21-mediated resistance. These studies indicate that BSMV-VIGS is a powerful tool for dissecting the genetic pathways of disease resistance in hexaploid wheat.

Gene Expression Regulation, Plant↗
PubMed1994

Microbial attachment and feed digestion in the rumen.

Direct microscopic examination of the rumen and its contents shows microbial populations largely attached to feed particles in the digesta. Most feeds contain a surface layer that is resistant to attachment and therefore to digestion. Infiltration of these recalcitrant epidermal layers through damage sites or through focused enzymatic attack is essential for initiation of the digestive process. Proliferation of primary colonizing cells produces glycocalyx-enclosed microcolonies. Secondary colonizers from the ruminal fluid associate with microcolonies, resulting in the formation of multispecies microbial biofilms. These metabolically related organisms associate with their preferred substrates and produce the myriad of enzymes necessary for the digestion of chemically and structurally complex plant tissues. Upon accessing the internal, enzyme-susceptible tissues, microbial "digestive consortia" attach to a variety of nutrients, including protein, cellulose, and starch and digest insoluble feed materials from the inside out. Substances that prevent microbial attachment or promote detachment (e.g., condensed tannins, methylcellulose) can completely inhibit cellulose digestion. As the microbial consortium matures and adapts to a particular type of feed, it becomes inherently stable and its participant microorganisms are notoriously difficult to manipulate due to the impenetrable nature of biofilms. Properties of feed that place constraints on microbial attachment and biofilm formation can have a profound effect on both the rate and extent of feed digestion in the rumen. Developments in feed processing (i.e., chemical and physical), plant breeding, and genetic engineering (both of ruminal microorganisms and plants) that overcome these constraints through the promotion of microbial attachment and biofilm formation could substantially benefit ruminant production.

Animal Feed↗
PubMed2001

Tobacco plants that lack expression of functional nitrate reductase in roots show changes in growth rates and metabolite accumulation.

When tobacco is provided with a high nitrate supply, only a small amount of the nitrate taken up by the roots is immediately assimilated inside the roots, while the majority is transported to the leaves where it is reduced to ammonium. To elucidate the importance of root nitrate assimilation, tobacco plants have been engineered that showed no detectable nitrate reductase activity in the roots. These plants expressed the nitrate reductase structural gene nia2 under control of the leaf-specific potato promoter ST-LS1 in the nitrate reductase-mutant Nia30 of Nicotiana tabacum. Homozygous T2-transformants grown in sand or hydroponics with 5.1 mM nitrate had approximately 55-70% of wild-type nitrate reductase acivity in leaves, but lacked nitrate reductase acivity in roots. These plants showed a retarded growth as compared with wild-type plants. The activation state of nitrate reductase was unchanged; however, diurnal variation of nitrate reductase acivity was not as pronounced as in wild-type plants. The transformants had higher levels of nitrate in the leaves and reduced amounts of glutamine both in leaves and roots, while roots showed higher levels of hexoses (3-fold) and sucrose (10-fold). It may be concluded that the loss of nitrate reductase acivity in the roots changes the allocation of reduced nitrogen compounds and sugars in the plant. These plants will be a useful tool for laboratories studying nitrate assimilation and its interactions with carbon metabolism.

Biological Transport↗
PubMedDate not supplied

[Microprotoplasts as an efficient technique for chromosome transfer between incompatible plant species].

The perspectives of restricted plant genome transfer by means of fusion of isolated microprotoplasts containing one or few chromosomes with recipient protoplasts are considered. Efficiency of the usage of antimicrotubular compounds such as phosphoroamidates (amiprophosmethyl and cremart), dinitroanilines (oryzalin) as well as propizamide and microtubule organising center disrupters (griseofulvin and phenylcarbamates) for micronucleation are analyzed. Advantages of the combined usage of antimicrotubular drugs and cytochalasin B as disrupter of actin filaments for enhanced yield of microprotoplasts are considered. Results of subsequent establishment of microprotoplast-mediated chromosome transfer technique is summarized. The examples of successful microprotoplast-mediated transfer of individual chromosomes from a donor potato line into mesophyl protoplasts of Nicotiana tabacum and into recipient cells of wild tomato (Lycopersicon peruvianum) with subsequent selection and regeneration of hybrids are considered. Development of alternative methods of partial genome transfer using microprotoplasts produced from plant gametes (microspores) is presented. The advantages of microprotoplast-mediated transfer of chromosomes as an efficient technique of parasexual crossing in comparison with traditional somatic hybridization are discussed.

Chromosomes, Plant↗
PubMedDate not supplied

[Construction of the cybrid transplastomic Brassica napus plants containing Lesquerella fendleri chloroplasts].

Transferring of Lesquerella fendleri genetically transformed plastids to Brassica napus plants has been performed with the somatic hybridization method. The plastome of the previously engineered transplastomic L. fendleri plants contained the aadA16gfp selective marker gene conferring spectinomycin/streptomycin resistance and green fluorescence under UV light. The protoplasts of B. napus chlorophyll-deficient plants were fused with gamma-irradiated protoplasts of L. fendleri transplastomic plants. A total of 59 green hybrid colonies have been isolated followed by spectinomycin/streptomycin selection. Shoot regeneration has been observed for two cell lines. Morphologically normal plants have been regenerated for one of them. PCR and isozyme analyses showed that the plants were transplastomic cybrids containing B. napus nuclei and L. fendleri transformed chloroplasts.

Brassica napus↗
PubMed2005

Transfer of transformed chloroplasts from Nicotiana tabacum to the Lycium barbarum plants.

Plastid transformation is an attractive technology for obtaining crop plants with new useful characteristics and for fundamental researches of plastid functioning and nuclear-plastid interaction. The aim of our experiments was to obtain plants with Lycium barbarum nucleus and transformed Nicotiana tabacum plastids. Plastome of previously engineered transplastomic tobacco plants contains reporter uidA gene and selective aadA gene that confers resistance to antibiotics spectinomycin and streptomycin. Asymmetric somatic hybridization was performed for transferring transformed tobacco plastids from transplastomic tobacco plants into recipient L. barbarum wild type plants. Hybrid L. barbarum plants containing transformed tobacco plastome with active aadA and uidA genes were obtained as a result of the experiments. The work shows the possibility of obtaining transplastomic plants by transferring the transformed plastids to remote species by using somatic hybridization technology. The developed technique is especially effective for obtaining transplastomic plants that have low regeneration and transformation ability.

Chloroplasts↗
PubMed2004

Genetic engineering of glycinebetaine synthesis in tomato protects seeds, plants, and flowers from chilling damage.

Tomato (Lycopersicon esculentum Mill.) plants, which normally do not accumulate glycinebetaine (GB), are susceptible to chilling stress. Exposure to temperatures below 10 degrees C causes various injuries and greatly decreases fruit set in most cultivars. We have transformed tomato (cv. Moneymaker) with a chloroplast-targeted codA gene of Arthrobacter globiformis, which encodes choline oxidase to catalyze the conversion of choline to GB. These transgenic plants express codA and synthesize choline oxidase, while accumulating GB in their leaves and reproductive organs up to 0.3 and 1.2 micromol g(-1) fresh weight (FW), respectively. Their chloroplasts contain up to 86% of total leaf GB. Over various developmental phases, from seed germination to fruit production, these GB-accumulating plants are more tolerant of chilling stress than their wild-type counterparts. During reproduction, they yield, on average, 10-30% more fruit following chilling stress. Endogenous GB contents as low as 0.1 micromol g(-1) FW are apparently sufficient to confer high levels of tolerance in tomato plants, as achieved via transformation with the codA gene. Exogenous application of either GB or H2O2 improves both chilling and oxidative tolerance concomitant with enhanced catalase activity. These moderately increased levels of H2O2 in codA transgenic plants, as a byproduct of choline oxidase-catalyzed GB synthesis, might activate the H2O2-inducible protective mechanism, resulting in improved chilling and oxidative tolerances in GB-accumulating codA transgenic plants. Thus, introducing the biosynthetic pathway of GB into tomato through metabolic engineering is an effective strategy for improving chilling tolerance.

Alcohol Oxidoreductases↗
PubMed2001

Introduction of bacterial metabolism into higher plants by polycistronic transgene expression.

Multiple-gene transformation is required to improve or change plant metabolisms effectively; but this many-step procedure is time-consuming and costing. We succeeded in the metabolic engineering of tobacco plants by introducing multiple genes as a bacteria-type operon into a plastid genome. The tobacco plastid was transformed with a polycistron consisting of three bacterial genes for the biosynthesis of a biodegradable polyester, polyhydroxybutyrate (PHB). Accumulation of PHB in the leaves of the transgenic tobacco indicated that the introduced genes were polycistronically expressed. This "phyto-fermentation" system can be used in plant production of various chemical commodities and pharmaceuticals.

Acetyl-CoA C-Acyltransferase↗
PubMed1989

Intact soil-core microcosms for evaluating the fate and ecological impact of the release of genetically engineered microorganisms.

Intact soil-core microcosms were studied to determine their applicability for evaluating the transport, survival, and potential ecosystem effects of genetically engineered microorganisms before they are released into the environment. Soil-core microcosms were planted with wheat and maize seeds and inoculated with Azospirillum lipoferum SpBr17 and SpRG20a Tn5 mutants, respectively. Microcosm leachate, rhizosphere soil, plant endorhizosphere, insects, and xylem exudate were sampled for A. lipoferum Tn5 mutant populations. A. lipoferum Tn5 populations, determined by most-probable-number technique-DNA hybridization, varied from below detection to 10 g of dry root in the rhizosphere, with smaller populations detected in the endorhizosphere. Intact soil-core microcosms were found to maintain some of the complexities of the natural ecosystem and should be particularly useful for initial evaluations of the fate of plant-associated genetically engineered bacteria.

Journal Article↗