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PubMed2005

Silicon alleviates the deleterious salt effect on tomato plant growth by improving plant water status.

In order to investigate the role of Si in alleviating the deleterious effects of salinity on tomato plant growth, the tomato cultivar Moneymaker was grown with 0 or 80mM NaCl combined with 0 and 2.5mM Si. Plant growth parameters, salt accumulation in plant tissues and plant water relations were analysed. Si treatment did not alter salt input into the plant or salt distribution between plant organs. There were non-significant differences in plant water uptake, but plant water content in salinised plants supplied with Si was 40% higher than in salinised plants that were not supplied with Si. Plants treated with NaCl alone showed a reduction in plant dry weight and total plant leaf area of 55% and 58%, respectively, while the reduction in plants treated with NaCl plus Si was only 31% and 22%, respectively. Leaf turgor potential and net photosynthesis rates were 42% and 20% higher in salinised plants supplied with Si than in salinised plants that were not supplied with Si. Water use efficiency calculated from instantaneous gas exchange parameters and as the ratio between plant dry matter and plant water uptake were, respectively, 17% and 16% higher in salinised plants supplied with Si. It can be concluded that Si improves the water storage within plant tissues, which allows a higher growth rate that, in turn, contributes to salt dilution into the plant, mitigating salt toxicity effects.

Carbon Dioxide↗
PubMed2004

Plant perceptions of plant growth-promoting Pseudomonas.

Plant-associated Pseudomonas live as saprophytes and parasites on plant surfaces and inside plant tissues. Many plant-associated Pseudomonas promote plant growth by suppressing pathogenic micro-organisms, synthesizing growth-stimulating plant hormones and promoting increased plant disease resistance. Others inhibit plant growth and cause disease symptoms ranging from rot and necrosis through to developmental dystrophies such as galls. It is not easy to draw a clear distinction between pathogenic and plant growth-promoting Pseudomonas. They colonize the same ecological niches and possess similar mechanisms for plant colonization. Pathogenic, saprophytic and plant growth-promoting strains are often found within the same species, and the incidence and severity of Pseudomonas diseases are affected by environmental factors and host-specific interactions. Plants are faced with the challenge of how to recognize and exclude pathogens that pose a genuine threat, while tolerating more benign organisms. This review examines Pseudomonas from a plant perspective, focusing in particular on the question of how plants perceive and are affected by saprophytic and plant growth-promoting Pseudomonas (PGPP), in contrast to their interactions with plant pathogenic Pseudomonas. A better understanding of the molecular basis of plant-PGPP interactions and of the key differences between pathogens and PGPP will enable researchers to make more informed decisions in designing integrated disease-control strategies and in selecting, modifying and using PGPP for plant growth promotion, bioremediation and biocontrol.

Immunity, Innate↗
PubMed1999

Environmental behavior of explosives in groundwater from the Milan Army Ammunition Plant in aquatic and wetland plant treatments. Removal, mass balances and fate in groundwater of TNT and RDX.

Phytoremediation of 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in groundwater using constructed wetlands is a potentially economical remediation alternative. To evaluate Explosives removal and fate was evaluated using hydroponic batch incubations of plant and substrate treatments with explosives-contaminated groundwater amended with [U-14C]-TNT or [U-14C]-RDX. Plants and substrates were collected from a small-scale wetland constructed for explosives removal, and groundwater originated from a local aquifer at the Milan Army Ammunition Plant. The study surveyed three aquatic, four wetland plant species and two substrates in independent incubations of 7 days with TNT and 13 days with RDX. Parent compounds and transformation products were followed using 14C and chemical (HPLC) analyses. Mass balance of water, plants, substrates and air was determined. It was demonstrated that TNT disappeared completely from groundwater incubated with plants, although growth of most plants except parrot-feather was low in groundwater amended to contain 1.6 to 3.4 mg TNT L-1. Highest specific removal rates were found in submersed plants in water star-grass and in all emergent plants except wool-grass. TNT declined less with substrates, and least in controls without plants. Radiolabel was present in all plants after incubation. Mineralization to 14CO2 was very low, and evolution into 14C-volatile organics negligible. RDX disappeared less rapidly than TNT from groundwater. Growth of submersed plants was normal, but that of emergent plants reduced in groundwater amended to contain 1.5 mg RDX L-1. Highest specific RDX removal rates were found in submersed plants in elodea, and in emergent plants in reed canary grass. RDX failed to disappear with substrates. Mineralization to 14CO2 was low, but relatively higher than in the TNT experiment. Evolution into 14C-volatile organics was negligible. Important considerations for using certain aquatic and wetland plants in constructed wetlands aimed at removing explosives from water are: (1) plant persistence at the explosives level to which it is exposed, (2) specific plant-mass based explosives removal rates, (3) plant productivity, and (4) fate of parent compounds and transformation products in water, plants, and sediments.

Environmental Pollution↗
PubMed2000

Expression of the plant cyclin-dependent kinase inhibitor ICK1 affects cell division, plant growth and morphology.

The plant CDK inhibitor ICK1 was identified previously from Arabidopis thaliana with its inhibitory activity characterized in vitro. ICK1 displayed several structural and functional features that are distinct from known animal CDK inhibitors. Despite the initial characterization, there is no information on the functions of any plant CDK inhibitor in plants. To gain insight into ICK1 functions in vivo and the role of cell division during plant growth and development, transgenic plants were generated expressing ICK1 driven by the cauliflower mosaic virus 35S promoter. In comparison to control plants, growth was significantly inhibited in transgenic 35S-ICK1 plants, with some plants weighing <10% of wild-type plants at the 3 week stage. Most organs of 35S-ICK1 plants were smaller. There were also modifications in plant morphology such as shape and serration of leaves and petals. The changes were so drastic that 35S-ICK1 plants with strong phenotype no longer resembled wild-type plants morphologically. Analyses showed that increased ICK1 expression resulted in reduced CDK activity and reduced the number of cells in these plants. Cells in 35S-ICK1 plants were larger than corresponding cells in control plants. These results demonstrate that ICK1 acts as a CDK inhibitor in the plant, and the inhibition of cell division by ICK1 expression has profound effects on plant growth and development. They also suggest that alterations of plant organ shape can be achieved by restriction of cell division.

Arabidopsis↗
PubMed2000

Plants experiencing chronic internal exposure to ionizing radiation exhibit higher frequency of homologous recombination than acutely irradiated plants.

Ionizing radiation (IR) is a known mutagen responsible for causing DNA strand breaks in all living organisms. Strand breaks thus created can be repaired by different mechanisms, including homologous recombination (HR), one of the key mechanisms maintaining genome stability [A. Britt, DNA damage and repair in plants, Annu. Rev. Plant. Phys. Plant Mol. Biol., 45 (1996) 75-100; H. Puchta, B. Hohn, From centiMorgans to basepairs: homologous recombination in plants, Trends Plant Sci., 1 (1996) 340-348.]. Acute or chronic exposure to IR may have different influences on the genome integrity. Although in a radioactively contaminated environment plants are mostly exposed to chronic pollution, evaluation of both kinds of influences is important. Estimation of the frequency of HR in the exposed plants may serve as an indication of genome stability. We used previously generated Arabidopsis thaliana and Nicotiana tabacum plants, transgenic for non-active versions of the beta-glucoronidase gene (uidA) [P. Swoboda, S. Gal, B. Hohn, H. Puchta, Intrachromosomal homologous recombination in whole plants, EMBO J., 13 (1994) 484-489; H. Puchta, P. Swoboda, B. Hohn, Induction of homologous DNA recombination in whole plants, Plant, 7 (1995) 203-210.] serving as a recombination substrate, to study the influence of acute and chronic exposure to IR on the level of HR as example of genome stability in plants. Exposure of seeds and seedlings to 0.1 to 10.0 Gy 60Co resulted in increased HR frequency, although the effect was more pronounced in seedlings. For the study of the influence of chronic exposure to IR, plants were grown on two chemically different types of soils, each artificially contaminated with equal amounts of 137Cs. We observed a strong and significant correlation between the frequency of HR in plants, the radioactivity of the soil samples and the doses of radiation absorbed by plants (in all cases r0.9, n=6, P<0.05). In addition, we noted that plants grown in soils with different chemical composition, but equal radioactivity, exhibited different levels of HR, dependent upon the absorbed dose of radiation. Remarkably, we observed a much higher frequency of HR in plants exposed to chronic irradiation when compared to acutely irradiated plants. Although acute application of 0.1-0.5 Gy did not lead to an increase of frequency of HR, the chronic exposure of the plants to several orders of magnitude lower dose of 200 muGy led to a 5-6-fold induction of the frequency of HR as compared to the control.

DNA Damage↗
PubMed2005

Effect of Cry3Bb1-expressing transgenic corn on plant-to-plant movement by western corn rootworm larvae (Coleoptera: Chrysomelidae).

Dispersal of larvae of the western corn rootworm, Diabrotica virgifera virgifera LeConte, in specific combinations of transgenic corn expressing the Cry3Bb1 protein and nontransgenic, isoline corn was evaluated in a 2-yr field study. In total, 1,500 viable western corn rootworm eggs were infested in each subplot. Each year, plant damage and larval recovery were evaluated among four pedigree combinations (straight transgenic; straight nontransgenic corn; nontransgenic corn with a transgenic central, infested plant; and transgenic corn with a nontransgenic central, infested plant) on six sample dates between egg hatch and pupation. For each subplot, the infested plant, three successive plants down the row (P1, P2, and P3), the closest plant in the adjacent row of the plot, and a control plant were sampled. The number of western corn rootworm larvae recovered from transgenic rootworm-resistant plants adjacent to infested nontransgenic plants was low and not statistically significant in either 2001 or 2002. In 2001, significantly fewer larvae were recovered from transgenic rootworm-resistant plants than from nontransgenic plants when both were adjacent to infested, nontransgenic plants. In 2002, significantly more neonate western corn rootworm larvae were recovered from nontransgenic plants adjacent to infested, transgenic rootworm-resistant plants than nontransgenic plants adjacent to infested, nontransgenic plants on the second sample date. Together, these data imply that both neonate and later instar western corn rootworm larvae prefer nontransgenic roots to transgenic rootworm-resistant roots when a choice is possible. However, when damage to the infested, nontransgenic plant was high, western corn rootworm larvae apparently moved to neighboring transgenic rootworm-resistant plants and caused statistically significant, although only marginally economic, damage on the last sample date in 2001. Implications of these data toward resistance management plan are discussed.

Animals↗
PubMed2002

Plant-to-plant communication mediating in-flight orientation of Aphidius ervi.

Broad bean plants (Viciafaba) infested by the pea aphid, Acyrthosiphonpisum, play akey role in the in-flightorientation of the parasitoidAphidius ervi, by producing host-induced synomones (HIS). These volatiles are herbivore-specific and are systemically released from insect-free parts of an infested plant, suggesting the existence of an elicitor circulating throughout the plant. This study was designed to investigate whether the plant metabolic changes, leading to HIS biosynthesis and emission, can in some way trigger similar responses in neighboring plants through aerial and/or root communication. Uninfested broad bean plants maintained in the same pot together with plants infested by A. pisum became more attractive towards A. ervi females when tested in a wind-tunnel bioassay. This change was not observed when root contact was prevented among plants that had their aerial parts in close proximity, suggesting that an exudate from the roots of the infested plant may cause the induction of the attractive volatiles in uninfested plants. Broad bean plants grown hydroponically also produce pea aphid induced signals that attract A. ervi. When an intact (uninfested) plant was placed in a hydroponic solution previously used to grow a pea aphid-infested plant, it became attractive to parasitoids, while an intact plant placed in a solution previously used to grow an intact plant did not undergo such a change. These results indicate that plant-to-plant signaling in this tritrophic system may occur at the rhizosphere level and is most likely mediated by a systemically translocated elicitor.

Animals↗
PubMed2006

Impact of botanical pesticides derived from Melia azedarach and Azadirachta indica plants on the emission of volatiles that attract Parasitoids of the diamondback moth to cabbage plants.

Herbivorous and carnivorous arthropods use chemical information from plants during foraging. Aqueous leaf extracts from the syringa tree Melia azedarach and commercial formulations from the neem tree Azadirachta indica, Neemix 4.5, were investigated for their impact on the flight response of two parasitoids, Cotesia plutellae and Diadromus collaris. Cotesia plutellae was attracted only to Plutella xylostella-infested cabbage plants in a wind tunnel after an oviposition experience. Female C. plutellae did not distinguish between P. xylostella-infested cabbage plants treated with neem and control P. xylostella-infested plants. However, females preferred infested cabbage plants that had been treated with syringa extract to control infested plants. Syringa extract on filter paper did not attract C. plutellae. This suggests that an interaction between the plant and the syringa extract enhances parasitoid attraction. Diadromus collaris was not attracted to cabbage plants in a wind tunnel and did not distinguish between caterpillar-damaged and undamaged cabbage plants. Headspace analysis revealed 49 compounds in both control cabbage plants and cabbage plants that had been treated with the syringa extract. Among these are alcohols, aldehydes, ketones, esters, terpenoids, sulfides, and an isothiocyanate. Cabbage plants that had been treated with the syringa extract emitted larger quantities of volatiles, and these increased quantities were not derived from the syringa extract. Therefore, the syringa extract seemed to induce the emission of cabbage volatiles. To our knowledge, this is the first example of a plant extract inducing the emission of plant volatiles in another plant. This interesting phenomenon likely explains the preference of C. plutellae parasitoids for cabbage plants that have been treated with syringa extracts.

Animals↗
PubMed2001

Systemic spread of an RNA insect virus in plants expressing plant viral movement protein genes.

Flock house virus (FHV), a single-stranded RNA insect virus, has previously been reported to cross the kingdom barrier and replicate in barley protoplasts and in inoculated leaves of several plant species [Selling, B. H., Allison, R. F. & Kaesberg, P. (1990) Proc. Natl. Acad. Sci. USA 87, 434-438]. There was no systemic movement of FHV in plants. We tested the ability of movement proteins (MPs) of plant viruses to provide movement functions and cause systemic spread of FHV in plants. We compared the growth of FHV in leaves of nontransgenic and transgenic plants expressing the MP of tobacco mosaic virus or red clover necrotic mosaic virus (RCNMV). Both MPs mobilized cell-to-cell and systemic movement of FHV in Nicotiana benthamiana plants. The yield of FHV was more than 100-fold higher in the inoculated leaves of transgenic plants than in the inoculated leaves of nontransgenic plants. In addition, FHV accumulated in the noninoculated upper leaves of both MP-transgenic plants. RCNMV MP was more efficient in mobilizing FHV to noninoculated upper leaves. We also report here that FHV replicates in inoculated leaves of six additional plant species: alfalfa, Arabidopsis, Brassica, cucumber, maize, and rice. Our results demonstrate that plant viral MPs cause cell-to-cell and long-distance movement of an animal virus in plants and offer approaches to the study of the evolution of viruses and mechanisms governing mRNA trafficking in plants as well as to the development of promising vectors for transient expression of foreign genes in plants.

Biological Transport↗
PubMed2005

Effect of high plant sterol-enriched diet and cholesterol absorption inhibitor, SCH 58235, on plant sterol absorption and plasma concentrations in hypercholesterolemic wild-type Kyoto rats.

BACKGROUND AND AIMS: Plant sterols are widely distributed in human diet but are poorly absorbed so that their plasma levels are very low. However, when fed in large amounts, they lower plasma cholesterol levels by interfering with cholesterol absorption. We have studied the effect of 4 weeks of feeding a chow diet supplemented with 1% plant sterols [brassicasterol (6.3%), campesterol (28.5%), stigmasterol (15.6%) and sitosterol (49.6%)], with or without SCH 58235 (a derivative of ezetimibe), 30 mg/kg per day, known to suppress intestinal cholesterol absorption, on plasma, tissue, biliary, and fecal sterols in Wistar and wild-type Kyoto (WKY) rats, and their metabolism by intestinal bacteria. METHODS: After 2 weeks of feeding control or experimental diet, rats were given [3alpha-(3)H]sitosterol intravenously and [4-(14)C]sitosterol by mouth, and blood was collected after 1, 2, 3, and 5 days after labeling to determine sitosterol absorption. Feces were collected during the last 3 days and freeze dried. At the end of feeding, bile fistulas were created in 3 rats of each strain and bile was collected for 1 hour. All rats were then sacrificed and plasma and liver were collected for sterol measurements and activities of hepatic HMG-CoA reductase, cholesterol 7alpha-hydroxylase, and cholesterol 27-hydroxylase. RESULTS: Wild-type Kyoto rats were hypercholesterolemic compared to Wistar rats and had increased plant sterols in the plasma. Plasma cholesterol tended to be lower in WKY rats after feeding with plant sterol-enriched diet whereas plant sterol levels rose to approximately 31% of plasma sterols in WKY and 14% in Wistar rats. However, brassicasterol and stigmasterol, with a double bond at C-22, constituted less than 3.5% of total plasma plant sterols. After feeding, biliary plant sterols increased 2.25-fold in Wistar and 1.5-fold in WKY rats, suggesting less hepatic clearance in WKY rats. SCH 58235 feeding significantly increased plasma as well as biliary cholesterol levels in both the untreated and plant sterol-fed WKY rats, and the plasma plant sterols showed a tendency to increase but did not reach significant level. Intestinal bacteria in both rat strains metabolized all plant sterols to mainly the 5beta-H-stanols. However, the C-22 double bond was stable to bacterial degradation. Intestinal absorption of sitosterol and cholesterol was increased 1.5- and 1.3-fold, respectively, in the WKY rats as compared to the Wistar rats, and plant sterol feeding lowered absorption of these sterols in both strains. Absorption of both these sterols was also lowered in SCH 58235-treated rats in both strains and was further lowered when SCH 58235 and plant sterols were simultaneously fed. The activity of the rate-limiting enzyme, HMG-CoA reductase, was increased 1.57-fold in Wistar rats and 1.27-fold in WKY rats that were fed plant sterols as compared to untreated rats. CONCLUSIONS: (1) Plant sterol absorption was increased whereas hepatic elimination of all sterols was diminished in WKY rats accounting for elevated cholesterol and plant sterol levels. (2) The 1% plant sterol-enriched diet tended to lower plasma cholesterol levels whereas SCH 58235 feeding significantly increased plasma cholesterol levels in the WKY rats. (3) Intestinal absorption of sterols with C-22 double bond is diminished and the side-chain double bond is resistant to intestinal bacteria.

Animals↗
PubMedDate not supplied

Determination of plant sterol oxidation products in plant sterol enriched spreads, fat blends, and plant sterol concentrates.

Plant sterols (PS) are very stable molecules but may undergo oxidation due to the presence of a double bond in the ring structure. In order to assess whether this occurs during heating and storage, an analytical procedure was developed for the determination of concentration levels and identity of PS oxidation products in functional food ingredients and products. The method is based on cold saponification, solvent extraction of unsaponifiables, isolation of sterol oxidation products by means of liquid chromatography, and final analysis by gas chromatography (GC) with flame ionization detection. Identification of the key PS oxidation products was performed by means of GC-mass spectrometry (GC-MS). Isotope dilution MS was used to verify the absence of the formation of potential artifacts by the method. The method described is applicable to spreads (containing 20-65% water), oils, sterol esters, pure sterols, and fat extracts from food. The between-day reproducibility of the total content of sterol oxidation products in control samples sample was 8%, and of individual sterol oxidation products, 6-15%. The recovery of sterol oxidation products was 91%. The limit of detection was 0.1 mg/kg.

Gas Chromatography-Mass Spectrometry↗
PubMed2005

Within-plant variation in induced defence in developing leaves of cotton plants.

According to optimal defence theory (ODT) plants should invest in stronger defence in the most valuable parts, such as reproductive or young tissue. Cotton plants are known to express high resistance to herbivore feeding in the developing leaves at the top of the plant after herbivore-damage. Cotton plants also have developing leaves on side shoots from the nodes all along the plant. This allowed us to investigate within-plant distribution of defence between younger tissues at different locations on the plant. We found that all developing leaves showed increased resistance to feeding by larvae of the generalist moth Spodoptera littoralis after herbivore damage to leaves of the plant. An increase in the concentration of secondary compounds, terpenoid aldehydes, was found in developing leaves both at the top of the plant and on the side shoots. However, the resistance was stronger in the top leaves than in the side shoot leaves, showing that there is intra-plant variation in the induced response between different leaves of the same age. After the initial damage, larval feeding mainly occurred on the older, fully developed true leaves. Furthermore, the herbivore-induced resistance in the developing leaves reduced upward movement of feeding larvae on the plant and reduced the feeding on the upper parts of the plant over a period of at least 6 days. The plant thus benefits from defending all developing leaves by directing feeding to older, less valuable leaves and lower parts of the plant. The observed distribution of defence within cotton plants supports ODT.

Age Factors↗
PubMed2004

Role of egg density on establishment and plant-to-plant movement by western corn rootworm larvae (Coleoptera: Chrysomelidae).

The effect of egg density on establishment and dispersal of larvae of the western corn rootworm, Diabrotica virgifera virgifera LeConte, was evaluated in a 3-yr field study. Implications of these data for resistance management plans for Bt crops are discussed. Viable egg levels of 100, 200, 400, 800, and 1600 eggs per infested plant were evaluated in 2000, 2001, and 2002. A 3200 viable egg level was also tested in 2001 and 2002. All eggs were infested on one plant per subplot in a field that was planted to soybean, Glycine max (L.), in the previous year. For each subplot, the infested plant, three plants down the row, the closest plant in the adjacent row of the plot, and a control plant at least 1.5 m from any infested plant (six plants total) were sampled. In 2000, there were five sample dates between egg hatch and pupation, and in 2001 and 2002, there were six sample dates. On each sample date, four replications of each egg density were sampled for both larval recovery and plant damage. Initial establishment on a corn plant seemed to not be density-dependent because a similar percentage of larvae was recovered from all infestation rates. Plant damage and, secondarily, subsequent postestablishment larval movement were density-dependent. Very little damage and postestablishment movement occurred at lower infestation levels, but significant damage and movement occurred at higher infestation rates. Movement generally occurred at a similar time as significant plant damage and not at initial establishment, so timing of movement seemed to be motivated by available food resources rather than crowding. At the highest infestation level in 2001, significant movement three plants down the row and across the 0.76 m row was detected, perhaps impacting refuge strategies for transgenic corn.

Animals↗
PubMed2002

The CDK inhibitor NtKIS1a is involved in plant development, endoreduplication and restores normal development of cyclin D3; 1-overexpressing plants.

Plant development requires stringent controls between cell proliferation and cell differentiation. Proliferation is positively regulated by cyclin dependent kinases (CDKs). Acting in opposition to CDKs are CDK inhibitors (CKIs). The first tobacco CKI (NtKIS1a) identified was shown to inhibit in vitro the kinase activity of CDK/cyclin complexes and to interact with CDK and D-cyclins. However, these features, which are common to other plant and animal CKIs already characterised, did not provide information about the function of NtKIS1a in plants. Thus, to gain insight into the role of NtKIS1a and especially its involvement in cell proliferation during plant development, we generated transgenic Arabidopsis thaliana plants that overexpress NtKIS1a. These plants showed reduced growth with smaller organs that contained larger cells. Moreover, these plants displayed modifications in plant morphology. These results demonstrated that plant organ size and shape, as well as organ cell number and cell size, might be controlled by modulation of the single NtKIS1a gene activity. Since in mammals, D-cyclins control cell cycle progression in a CDK-dependent manner but also play a CDK independent role by sequestering the CKIs p27(Kip1) and p21(Cip1), we tested the significance of cyclin D-CKI interaction within a living plant. With this aim, NtKIS1a and AtCycD3;1 were overexpressed simultaneously in plants by two different methods. Our results demonstrated that overexpression of the CKI NtKIS1a restores essentially normal development in plants overexpressing AtCycD3;1, providing the first evidence of cyclin D-CKI co-operation within the context of a living plant.

Arabidopsis↗
PubMed2002

Effects of co-expressing the plant CDK inhibitor ICK1 and D-type cyclin genes on plant growth, cell size and ploidy in Arabidopsis thaliana.

The cyclin-dependent kinase (CDK) plays a crucial role in regulating the cell cycle of eukaryotic organisms including plants. From previous studies, it is known that ICK1, the first plant CDK inhibitor identified in Arabidopsis plants, interacts with Arath;CycD3;1 (CycD3) and Arath;CDKA;1 (Cdc2a). Overexpression of ICK1 has major effects on cell division, plant growth, and morphology. In this study, approaches were taken to determine the effects on transgenic 35S::ICK1 Arabidopsis plants of introducing another gene that could potentially modulate the activity of ICK1. F1 plants were obtained by crossing 35S::ICK1 plants with wild type (Wt) and transgenic plants expressing 35::GUS, 35S::CycD3, 35S::CycD2, or 35S::antiICK1 ( antiICK1 refers to antisense- ICK1). The major effects on plant growth and morphology observed in the 35S::ICK1 plants were partially reversed in the F1 plants from the crosses [35S::ICK1 x 35S::CycD2] and [35S::ICK1 x 35S::CycD3], and completely restored in the F1 plants from the cross [35S::ICK1 x 35S::antiICK1]. This observation was further supported by the results of ploidy analysis and structural characterization. Overexpression of CycD2 and CycD3 had the opposite effect on leaf cell size to the overexpression of ICK1. In addition, in ICK1-overexpressing plants, the CycD2 and CycD3 transcript levels increased, indicating a possible feedback regulation. The present results demonstrate that the interactions between ICK1 and D-type cyclins previously observed by the yeast two-hybrid and in vitro techniques are biologically relevant. These results illustrate the possibility of modifying plant growth and architecture dynamically by adjusting the levels of positive and negative cell-cycle regulators.

Antisense Elements (Genetics)↗
PubMed2003

Accumulation of perchlorate in tobacco plants: development of a plant kinetic model.

Previous studies have shown that tobacco plants are tolerant of perchlorate and will accumulate perchlorate in plant tissues. This research determined the uptake, translocation, and accumulation of perchlorate in tobacco plants. Three hydroponics growth studies were completed under greenhouse conditions. Depletion of perchlorate in the hydroponics nutrient solution and accumulation of perchlorate in plant tissues were determined at two-day intervals using ion chromatography. Perchlorate primarily accumulated in tobacco leaves, yielding a substantial storage capacity for perchlorate. Mass balance results show that perchlorate degradation was negligible in plants. Tobacco plants were shown to effectively accumulate perchlorate over a wide range of initial concentrations (10 ppb to 100 ppm) from the hydroponics solution. Results suggest that plants are potential plants for the phytoremediation of perchlorate. A mathematical model was developed to describe the distribution of perchlorate in tobacco plants under rapid growth conditions. The Plant Kinetic (PK) model defined a plant as a set of compartments, described by mass balance differential equations and plant-specific physiological parameters. Data obtained from a separate hydroponics growth study with multiple solution perchlorate concentrations were used to validate predicted root, stem, and leaf concentrations. There was good agreement between model predictions and measured concentrations in the plant. The model, once adequately validated, can be applied to other terrestrial plants and inorganic chemicals currently used for both phytoremediation and ecological risk assessment.

Kinetics↗
PubMed2006

Whole-plant growth stage ontology for angiosperms and its application in plant biology.

Plant growth stages are identified as distinct morphological landmarks in a continuous developmental process. The terms describing these developmental stages record the morphological appearance of the plant at a specific point in its life cycle. The widely differing morphology of plant species consequently gave rise to heterogeneous vocabularies describing growth and development. Each species or family specific community developed distinct terminologies for describing whole-plant growth stages. This semantic heterogeneity made it impossible to use growth stage description contained within plant biology databases to make meaningful computational comparisons. The Plant Ontology Consortium (http://www.plantontology.org) was founded to develop standard ontologies describing plant anatomical as well as growth and developmental stages that can be used for annotation of gene expression patterns and phenotypes of all flowering plants. In this article, we describe the development of a generic whole-plant growth stage ontology that describes the spatiotemporal stages of plant growth as a set of landmark events that progress from germination to senescence. This ontology represents a synthesis and integration of terms and concepts from a variety of species-specific vocabularies previously used for describing phenotypes and genomic information. It provides a common platform for annotating gene function and gene expression in relation to the developmental trajectory of a plant described at the organismal level. As proof of concept the Plant Ontology Consortium used the plant ontology growth stage ontology to annotate genes and phenotypes in plants with initial emphasis on those represented in The Arabidopsis Information Resource, Gramene database, and MaizeGDB.

Arabidopsis↗