Alterations of hydrogen peroxide (H2O2) levels have a profound impact on numerous signaling cascades orchestrating plant growth, development, and stress signaling, including programmed cell death. To expand the repertoire of known molecular mechanisms implicated in H2O2 signaling, we performed a forward chemical screen to identify small molecules that could alleviate the photorespiratory-induced cell death phenotype of Arabidopsisthaliana mutants lacking H2O2-scavenging capacity by peroxisomal catalase2. Here, we report the characterization of pakerine, an m-sulfamoyl benzamide from the sulfonamide family. Pakerine alleviates the cell death phenotype of cat2 mutants exposed to photorespiration-promoting conditions and delays dark-induced senescence in wild-type Arabidopsis leaves. By using a combination of transcriptomics, metabolomics, and affinity purification, we identified abnormal inflorescence meristem 1 (AIM1) as a putative protein target of pakerine. AIM1 is a 3-hydroxyacyl-CoA dehydrogenase involved in fatty acid β-oxidation that contributes to jasmonic acid (JA) and salicylic acid (SA) biosynthesis. Whereas intact JA biosynthesis was not required for pakerine bioactivity, our results point toward a role for β-oxidation-dependent SA production in the execution of H2O2-mediated cell death.
- MeSH
- Arabidopsis cytologie účinky léků genetika metabolismus MeSH
- buněčná smrt účinky léků MeSH
- buněčné dýchání účinky léků genetika MeSH
- cyklopentany metabolismus MeSH
- fotosyntéza účinky léků genetika MeSH
- fyziologický stres MeSH
- hydroponie metody MeSH
- kyselina salicylová metabolismus MeSH
- listy rostlin cytologie účinky léků metabolismus MeSH
- meristém cytologie účinky léků metabolismus MeSH
- multienzymové komplexy genetika metabolismus MeSH
- oxylipiny metabolismus MeSH
- peroxid vodíku antagonisté a inhibitory farmakologie MeSH
- proteiny huseníčku genetika metabolismus MeSH
- regulace genové exprese u rostlin * MeSH
- rostlinné buňky účinky léků metabolismus MeSH
- semena rostlinná účinky léků MeSH
- signální transdukce MeSH
- stanovení celkové genové exprese MeSH
- sulfonamidy chemická syntéza farmakologie MeSH
- transkriptom MeSH
- výpočetní biologie metody MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Chlorophyll fluorescence kinetic analysis has become an important tool in basic and applied research on plant physiology and agronomy. While early systems recorded the integrated kinetics of a selected spot or plant, later systems enabled imaging of at least the slower parts of the kinetics (20-ms time resolution). For faster events, such as the rise from the basic dark-adapted fluorescence yield to the maximum (OJIP transient), or the fluorescence yield decrease during reoxidation of plastoquinone A after a saturating flash, integrative systems are used because of limiting speed of the available imaging systems. In our new macroscopic and microscopic systems, the OJIP or plastonique A reoxidation fluorescence transients are directly imaged using an ultrafast camera. The advantage of such systems compared to nonimaging measurements is the analysis of heterogeneity of measured parameters, for example between the photosynthetic tissue near the veins and the tissue further away from the veins. Further, in contrast to the pump-and-probe measurement, direct imaging allows for measuring the transition of the plant from the dark-acclimated to a light-acclimated state via a quenching analysis protocol in which every supersaturating flash is coupled to a measurement of the fast fluorescence rise. We show that pump-and-probe measurement of OJIP is prone to artifacts, which are eliminated with the direct measurement. The examples of applications shown here, zinc deficiency and cadmium toxicity, demonstrate that this novel imaging platform can be used for detection and analysis of a range of alterations of the electron flow around PSII.
- MeSH
- Arabidopsis cytologie metabolismus MeSH
- Brassicaceae cytologie účinky léků metabolismus MeSH
- chlorofyl chemie metabolismus MeSH
- design vybavení MeSH
- fluorescence MeSH
- fluorescenční mikroskopie přístrojové vybavení metody MeSH
- fotosyntéza MeSH
- Glycine max cytologie účinky léků metabolismus MeSH
- kinetika MeSH
- listy rostlin cytologie MeSH
- mezofylové buňky metabolismus MeSH
- plastochinon metabolismus MeSH
- zinek metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Singlet oxygen produced from triplet excited chlorophylls in photosynthesis is a signal molecule that can induce programmed cell death (PCD) through the action of the OXIDATIVE STRESS INDUCIBLE 1 (OXI1) kinase. Here, we identify two negative regulators of light-induced PCD that modulate OXI1 expression: DAD1 and DAD2, homologs of the human antiapoptotic protein DEFENDER AGAINST CELL DEATH. Overexpressing OXI1 in Arabidopsis (Arabidopsis thaliana) increased plant sensitivity to high light and induced early senescence of mature leaves. Both phenomena rely on a marked accumulation of jasmonate and salicylate. DAD1 or DAD2 overexpression decreased OXI1 expression, jasmonate levels, and sensitivity to photooxidative stress. Knock-out mutants of DAD1 or DAD2 exhibited the opposite responses. Exogenous applications of jasmonate upregulated salicylate biosynthesis genes and caused leaf damage in wild-type plants but not in the salicylate biosynthesis mutant Salicylic acid induction-deficient2, indicating that salicylate plays a crucial role in PCD downstream of jasmonate. Treating plants with salicylate upregulated the DAD genes and downregulated OXI1 We conclude that OXI1 and DAD are antagonistic regulators of cell death through modulating jasmonate and salicylate levels. High light-induced PCD thus results from a tight control of the relative activities of these regulating proteins, with DAD exerting a negative feedback control on OXI1 expression.
- MeSH
- apoptóza genetika účinky záření MeSH
- Arabidopsis cytologie genetika metabolismus MeSH
- biosyntetické dráhy účinky léků genetika účinky záření MeSH
- cyklopentany metabolismus farmakologie MeSH
- fosfolipasy A1 genetika metabolismus MeSH
- kyselina salicylová metabolismus farmakologie MeSH
- listy rostlin cytologie genetika metabolismus MeSH
- mutace MeSH
- oxylipiny metabolismus farmakologie MeSH
- protein-serin-threoninkinasy genetika metabolismus MeSH
- proteiny huseníčku genetika metabolismus MeSH
- regulace genové exprese u rostlin účinky léků účinky záření MeSH
- regulátory růstu rostlin metabolismus farmakologie MeSH
- singletový kyslík metabolismus MeSH
- stanovení celkové genové exprese metody MeSH
- světlo MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
BACKGROUND: The southern African Oxalis radiation is extremely morphologically variable. Despite recent progress in the phylogenetics of the genus, there are few morphological synapomorphies supporting DNA-based clades. Leaflet anatomy can provide an understudied and potentially valuable source of information on the evolutionary history and systematics of this lineage. Fifty-nine leaflet anatomical traits of 109 southern African Oxalis species were assessed in search of phylogenetically significant characters that delineate clades. RESULTS: A combination of 6 leaflet anatomical traits (stomatal position, adaxial epidermal cells, abaxial epidermal cells, mesophyll, sheath around vascular tissue, degree of leaflet conduplication) clearly support various clades defined by previous DNA-based phylogenetic work. Other, mostly continuous leaflet anatomical traits were highly variable and showed less phylogenetic pattern. CONCLUSIONS: Major and unexpected findings include the transition from ancestral hypostomatic leaflets to adaxially-located stomata in the vast majority of southern African Oxalis, the loss of semi-swollen AB epidermal cells and the gain of swollen adaxial and abaxial epidermal cells in selected clades, and multiple changes from ancestral bifacial mesophyll to isobilateral or homogenous mesophyll types. The information gathered in this study will aid in the taxonomic revision of this speciose member of the Greater Cape Floristic Region and provide a basis for future hypotheses regarding its radiation.
- MeSH
- biologická evoluce MeSH
- cévní svazky rostlin cytologie MeSH
- duplikace genu MeSH
- fenotyp MeSH
- fylogeneze * MeSH
- kvantitativní znak dědičný MeSH
- listy rostlin anatomie a histologie cytologie genetika MeSH
- mezofylové buňky cytologie MeSH
- Oxalidaceae anatomie a histologie genetika MeSH
- průduchy rostlin cytologie MeSH
- trichomy cytologie MeSH
- Publikační typ
- časopisecké články MeSH
Nitrogen (N) is an essential macronutrient that limits agricultural productivity, and both low and high N supply have been suggested to alter plant growth. The overall aim of this work is to study the impact of nitrate (NO3(-)) in maize yield and the possible causes that induce this alteration. High NO3(-) doses did not increase the yield of maize grown neither in the field nor under controlled conditions. In fact, plants grown under controlled conditions for 45 days with NO3(-) concentrations over 5mM showed a decrease in biomass production. This reduction was perceptible in shoots prior to roots, where phytomer expansion was reduced. Cell size and number were also reduced in the leaves of plants with high NO3(-). This alteration was correlated with the increase of 1-aminocyclopropane-1-carboxylic acid in leaves, which was probably translocated from the roots in order to synthesize ethylene. Cytokinins (CKs) also showed a relevant role in this inhibitory effect, increasing in high NO3(-) plants with a reduction in root and shoot growth, inhibition of apical dominance and a strong decrease of leaf expansion, symptoms described previously as "CK syndrome". We propose that high NO3(-) inhibits maize growth by causing hormonal alterations that modify plant growth from cell to whole plant.
- MeSH
- aminokyseliny cyklické metabolismus MeSH
- biomasa MeSH
- cytokininy metabolismus MeSH
- dusičnany farmakologie MeSH
- dusík metabolismus MeSH
- epidermis rostlin cytologie účinky léků růst a vývoj MeSH
- kořeny rostlin cytologie účinky léků růst a vývoj MeSH
- kukuřice setá cytologie účinky léků růst a vývoj MeSH
- listy rostlin cytologie účinky léků růst a vývoj MeSH
- výhonky rostlin cytologie účinky léků růst a vývoj MeSH
- Publikační typ
- časopisecké články MeSH
This chapter gives examples of basic procedures of quantification of plant structures with the use of image analysis, which are commonly employed to describe differences among experimental treatments or phenotypes of plant material. Tasks are demonstrated with the use of ImageJ, a widely used public domain Java image processing program. Principles of sampling design based on systematic uniform random sampling for quantitative studies of anatomical parameters are given to obtain their unbiased estimations and simplified "rules of thumb" are presented. The basic procedures mentioned in the text are (1) sampling, (2) calibration, (3) manual length measurement, (4) leaf surface area measurement, (5) estimation of particle density demonstrated on an example of stomatal density, and (6) analysis of epidermal cell shape.
Polar auxin transport is a crucial process for control and coordination of plant development. Studies of auxin transport through plant tissues and organs showed that auxin is transported by a combination of phloem flow and the active, carrier-mediated cell-to-cell transport. Since plant organs and even tissues are too complex for determination of the kinetics of carrier-mediated auxin uptake and efflux on the cellular level, simplified models of cell suspension cultures are often used, and several tobacco cell lines have been established for auxin transport assays. However, there are very few data available on the specificity and kinetics of auxin transport across the plasma membrane for Arabidopsis thaliana suspension-cultured cells. In this report, the characteristics of carrier-mediated uptake (influx) and efflux for the native auxin indole-3-acetic acid and synthetic auxins, naphthalene-1-acetic and 2,4-dichlorophenoxyacetic acids (NAA and 2,4-D, respectively) in A. thaliana ecotype Landsberg erecta suspension-cultured cells (LE line) are provided. By auxin competition assays and inhibitor treatments, we show that, similarly to tobacco cells, uptake carriers have high affinity towards 2,4-D and that NAA is a good tool for studies of auxin efflux in LE cells. In contrast to tobacco cells, metabolic profiling showed that only a small proportion of NAA is metabolized in LE cells. These results show that the LE cell line is a useful experimental system for measurements of kinetics of auxin carriers on the cellular level that is complementary to tobacco cells.
- MeSH
- Arabidopsis cytologie růst a vývoj metabolismus MeSH
- biologický transport MeSH
- buněčné kultury MeSH
- fenotyp MeSH
- hypokotyl cytologie růst a vývoj metabolismus MeSH
- kotyledon cytologie růst a vývoj metabolismus MeSH
- kyselina 2,4-dichlorfenoxyoctová metabolismus MeSH
- kyseliny indoloctové metabolismus MeSH
- kyseliny naftalenoctové metabolismus MeSH
- listy rostlin cytologie růst a vývoj metabolismus MeSH
- metabolom MeSH
- regulátory růstu rostlin metabolismus MeSH
- semenáček cytologie růst a vývoj metabolismus MeSH
- tabák cytologie růst a vývoj metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
BACKGROUND AND AIMS: Cytokinins are positive regulators of shoot development. However, it has previously been demonstrated that efficient activation of the cytokinin biosynthesis gene ipt can cause necrotic lesions and wilting in tobacco leaves. Some plant pathogens reportedly use their ability to produce cytokinins in disease development. In response to pathogen attacks, plants can trigger a hypersensitive response that rapidly kills cells near the infection site, depriving the pathogen of nutrients and preventing its spread. In this study, a diverse set of processes that link ipt activation to necrotic lesion formation were investigated in order to evaluate the potential of cytokinins as signals and/or mediators in plant defence against pathogens. METHODS: The binary pOp-ipt/LhGR system for dexamethasone-inducible ipt expression was used to increase endogenous cytokinin levels in transgenic tobacco. Changes in the levels of cytokinins and the stress hormones salicylic, jasmonic and abscisic acid following ipt activation were determined by ultra-performance liquid chromatography-electrospray tandem mass spectrometry (UPLC-MS/MS). Trends in hydrogen peroxide content and lipid peroxidation were monitored using the potassium iodide and malondialdehyde assays. The subcellular distribution of hydrogen peroxide was investigated using 3,3'-diaminobenzidine staining. The dynamics of transcripts related to photosynthesis and pathogen response were analysed by reverse transcription followed by quantitative PCR. The effects of cytokinins on photosynthesis were deciphered by analysing changes in chlorophyll fluorescence and leaf gas exchange. KEY RESULTS: Plants can produce sufficiently high levels of cytokinins to trigger fast cell death without any intervening chlorosis - a hallmark of the hypersensitive response. The results suggest that chloroplastic hydrogen peroxide orchestrates the molecular responses underpinning the hypersensitive-like response, including the inhibition of photosynthesis, elevated levels of stress hormones, oxidative membrane damage and stomatal closure. CONCLUSIONS: Necrotic lesion formation triggered by ipt activation closely resembles the hypersensitive response. Cytokinins may thus act as signals and/or mediators in plant defence against pathogen attack.
- MeSH
- alkyltransferasy a aryltransferasy genetika MeSH
- buněčná smrt MeSH
- chlorofyl metabolismus MeSH
- chloroplasty genetika metabolismus MeSH
- cytokininy genetika metabolismus MeSH
- dexamethason farmakologie MeSH
- fotosyntéza genetika MeSH
- geneticky modifikované rostliny MeSH
- interakce hostitele a patogenu * MeSH
- listy rostlin cytologie genetika fyziologie MeSH
- nekróza genetika MeSH
- oxidační stres genetika MeSH
- peroxid vodíku metabolismus MeSH
- peroxidace lipidů MeSH
- průduchy rostlin fyziologie MeSH
- regulace genové exprese u rostlin účinky léků MeSH
- regulátory růstu rostlin genetika metabolismus MeSH
- tabák genetika mikrobiologie fyziologie MeSH
- umlčování genů MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- MeSH
- experimentální sarkom MeSH
- fibroblasty fyziologie chemie MeSH
- finanční podpora výzkumu jako téma MeSH
- kalibrace MeSH
- krysa rodu rattus MeSH
- kultivované buňky MeSH
- listy rostlin cytologie fyziologie MeSH
- pohyb buněk MeSH
- zobrazování trojrozměrné MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- zvířata MeSH
