64 research outputs found
Interaction between Hormone and Apoplastic ROS Signaling in Regulation of Defense Responses and Cell Death
No full textRegulation of cellular homeostasis is crucial for proper development, survival, defense responses, programmed cell death and ultimately survival. Maintaining cellular homeostasis requires tight regulation of multiple highly interactive signaling pathways. The apoplast lies at the frontier between the cell and the environment, where the plant perceives environmental cues. Since the apoplast is also a site for cell-to-cell communication, it has an important role in mediating plant-environment interactions. Reactive oxygen species (ROS) are known as both toxic agents and indispensable signaling molecules in all aerobic organisms. A ROS burst in the apoplast is one of the first measurable events produced in response to different biotic and abiotic stresses, eventually leading to the initiation of signal transduction pathways and altered gene expression. Apoplastic ROS signaling is well known to dynamically coordinate multiple signaling pathways in the activation of defense responses in plants. Dissection of the signaling crosstalk within such a signaling network could therefore reveal the molecular mechanisms underlying defense responses. Treatments with ozone (O3) have been adopted as an efficient tool to study apoplastic ROS signaling. Plants exposed to O3 trigger a ROS burst in the apoplast and induce extensive changes in gene expression and alteration of defense hormones, such as salicylic acid (SA), jasmonic acid (JA), and ethylene. Genetic variation in O3 sensitivity among Arabidopsis thaliana accessions or mutants highlights the complex genetic architecture of plant responses to ROS. To gain insight into the genetic basis of apoplastic ROS signaling, a recombinant inbred line (RIL) population from a reciprocal cross between two Arabidopsis accessions C24 (O3 tolerant) and Tenela (O3 sensitive) was used for quantitative trait loci (QTL) mapping. Through a combination of QTL mapping and transcriptomic analyses in the response to apoplastic-ROS treatment, three QTL regions containing several potential candidate genes were identified in this study. In addition, multiple mutants with varying O3-sensitivities were employed to dissect the signaling components involved in the early apoplastic ROS signaling and O3-triggered cell death. A combination of global and targeted gene expression profiling, genetic analysis, and cell death assays was performed to dissect the contribution of hormone signaling and various transcription factors to the regulation of apoplastic ROS-triggered gene expression and cell death. The contributions of SA, JA and ethylene were assessed through analysis of mutants deficient in these hormones, mutants with constitutively activated hormone signaling and the exogenous application of hormones. Plants with elevated SA levels were found to be associated with an attenuated O3 response, whereas simultaneous elimination of SA-dependent and SA- independent signaling components enhanced the response to apoplastic ROS treatment. JA could act as both a positive and negative modifier of apoplastic ROS signaling, which was enhanced when ethylene signaling was also impaired. However, transcriptome analysis of a triple mutant deficient in SA, JA and ethylene revealed that these hormones signaling only contributed part (about 30%) of early-apoplastic ROS-triggered changes in gene expression, suggesting multiple signaling pathways could be required to regulate the apoplastic ROS response via combinatorial or overlapping mechanisms.Solutason homeostaasin säätely on tärkeää yksilönkehityksen, puolustusvasteiden, ohjelmoidun solukuoleman ja lopulta selviytymisen kannalta. Homeostaasin säilyttäminen vaatii useiden keskenään vuorovaikutteisten viestinvälitysreittien tarkkaa säätelyä. Apoplasti sijaitsee solun ja sen ympäristön välisellä rajalla, josta kasvi aistii ympäristön muutoksia. Lisäksi apoplastin kautta kulkee osa solujen välisestä viestinnästä, joten sillä on tärkeitä tehtäviä kasvin ja sen ympäristön välisessä vuorovaikutuksessa. Reaktiiviset happilajit (reactive oxygen species, ROS) tunnetaan sekä myrkyllisinä yhdisteinä että korvaamattomina viestintämolekyyleinä kaikissa happea tarvitsevissa eliöissä. Yksi ensimmäisistä havaittavista vasteista erilaisiin bioottisiin ja abioottisiin stresseihin on apoplastissa tapahtuva reaktiivisten happilajien purkaus (ROS- purkaus), joka johtaa viestinvälitysreittien aktivaatioon ja muutoksiin geenien ilmentymisessä. Apoplastissa tapahtuva ROS-viestintä koordinoi dynaamisesti useita viestinvälitysketjuja kasvin puolustusvasteiden aktivoinnin aikana. Viestinvälitysketjujen ristivaikutusten analyysi saattaa siten paljastaa puolustusvasteen molekyylimekanismeja. Kasvien käsittelyä otsonilla (O3) käytetään tehokkaana työkaluna apoplastisen ROS-viestinnän tutkimuksessa. Kasvin otsonikäsittely laukaisee apoplastissa ROS-purkauksen ja aikaansaa suuria muutoksia geenien ilmentymisessä ja puolustukseen liittyvissä hormoneissa, kuten salisyylihapossa, jasmiinihapossa ja etyleenissä. Lituruohon (Arabidopsis thaliana) perinnöllinen muuntelu otsoniherkkyydessä korostaa kasvien ROS-vasteiden monimutkaista geneettistä rakennetta. Tässä työssä apoplastisen ROS-viestinnän geneettistä taustaa selvitettiin kvantitatiivisiin ominaisuuksiin vaikuttavien lokusten (QTL) kartoittamisella kahden Arabidopsis-ekotyypin, C24 (otsonikestävä) ja Tenela (otsoniherkkä), välisessä risteytysjälkeläistössä. Yhdistelemällä apoplastisen ROS-käsittelyn vaikutuksen QTL- kartoitusta ja transkriptomin tutkimusta löydettiin kolme QTL-aluetta, joissa on useita kandidaattigeenejä. Apoplastisen ROS-viestinnän ja otsonin käynnistämän solukuoleman parempaa ymmärtämistä varten tutkittiin lisäksi useita mutanttilinjoja, jotka eroavat toisistaan otsoniherkyydeltään. Laajaa ja kohdistettua geenien ilmentymisen profilointia, geneettistä analyysiä ja solukuolemakokeita käytettiin erittelemään hormoniviestinnän ja useiden transkriptiotekijöiden vaikutusta reaktiivisten happilajien käynnistämään apoplastiseen geenien ilmenemiseen ja solukuolemaan. Salisyylihapon, jasmiinihapon ja etyleenin tehtäviä tutkittiin analysoimalla mutanttilinjoja, joilta kyseisten hormonien viestintä oli estetty tai tehostettu, sekä lisäämällä hormoneja kasveille ulkoisesti. Kasvien, joilla oli korkeammat salisyylihappotasot, huomattiin reagoivan otsoniin vaimeammin, kun taas samanaikainen salisyylihaposta riippuvan ja riippumattoman viestinnän estäminen voimisti vastetta apoplastiseen ROS-käsittelyyn. Jasmiinihappo toimi sekä positiivisena että negatiivisena säätelijänä apoplastisessa ROS-viestinnässä, ja sen toiminta tehostui, kun myös etyleeniviestintä oli vaimennettu. Toisaalta kolmoismutantin, jolta oli vaimennettu kaikkien kolmen edellä mainitun hormonin viestintä, transkriptomitason analyysi paljasti, että näiden hormonien kautta kulkeva viestintä vaikuttaa vain osaan (noin 30%) varhaisista geenien ilmentymisen muutoksista vasteena apoplastiseen ROS-viestintään. Tästä voidaan päätellä, että useat viestinvälitysketjut säätelevät apoplastista ROS-vastetta päällekkäisin mekanismein.ei saavutettav
Salicylic acid signaling inhibits apoplastic reactive oxygen species signaling
No full textPeer reviewe
Development of the teaching simulator based on animated film to strengthening pedagogical competencies of prospective teachers
No full textGenome-Wide Identification of Arabidopsis LBD29 Target Genes Reveals the Molecular Events behind Auxin-Induced Cell Reprogramming during Callus Formation
No full textAuxin-induced callus formation represents an important cell reprogramming process during in vitro regeneration of plants, in which the pericycle or pericycle-like cells within plant organs are reprogrammed into the pluripotent cell mass termed callus that is generally required for subsequent regeneration of root or shoot. However, the molecular events behind cell reprogramming during auxin-induced callus formation are largely elusive. We previously identified that auxin-induced LATERAL ORGAN BOUNDARIES DOMAIN (LBD) transcription factors act as the master regulators to trigger auxin-induced callus formation. Here, by ChIP-seq (chromatin immunoprecipitation-based sequencing) and RNA sequencing approaches, we identified the potential LBD29 target genes at the genome-wide level and outlined the molecular events of LBD-triggered cell reprogramming during callus formation. We showed that LBD29 preferentially bound to the G-box (CACGTG) and TGGGC[C/T] motifs and potentially targeted > 350 genes, among which the genes related to methylation, reactive oxygen species (ROS) metabolism, cell wall hydrolysis and lipid metabolism were rapidly activated, while most of the light-responsive genes were suppressed by LBD29. Further examination of a few representative genes validated that they were targeted by LBD29 and participated in the regulation of cell reprogramming during callus formation. Our data not only outline a framework of the early molecular events behind auxin-induced cell reprogramming of callus formation, but also provide a valuable resource for identification of genes that regulate cell fate switch during in vitro regeneration of plants
A genetic framework for H2O2 induced cell death in Arabidopsis thaliana
No full textAbstract
Background
To survive in a changing environment plants constantly monitor their surroundings. In response to several stresses and during photorespiration plants use reactive oxygen species as signaling molecules. The Arabidopsis thaliana catalase2 (cat2) mutant lacks a peroxisomal catalase and under photorespiratory conditions accumulates H2O2, which leads to activation of cell death.
Methods
A cat2 double mutant collection was generated through crossing and scored for cell death in different assays. Selected double mutants were further analyzed for photosynthetic performance and H2O2 accumulation.
Results
We used a targeted mutant analysis with more than 50 cat2 double mutants to investigate the role of stress hormones and other defense regulators in H2O2-mediated cell death. Several transcription factors (AS1, MYB30, MYC2, WRKY70), cell death regulators (RCD1, DND1) and hormone regulators (AXR1, ERA1, SID2, EDS1, SGT1b) were essential for execution of cell death in cat2. Genetic loci required for cell death in cat2 was compared with regulators of cell death in spontaneous lesion mimic mutants and led to the identification of a core set of plant cell death regulators. Analysis of gene expression data from cat2 and plants undergoing cell death revealed similar gene expression profiles, further supporting the existence of a common program for regulation of plant cell death.
Conclusions
Our results provide a genetic framework for further study on the role of H2O2 in regulation of cell death. The hormones salicylic acid, jasmonic acid and auxin, as well as their interaction, are crucial determinants of cell death regulation
Additional file 7: Figure S6. of A genetic framework for H2O2 induced cell death in Arabidopsis thaliana
No full textMicroscopic cell death in dnd1, vtc1 and corresponding double mutants with cat2. Cell death is indicated with trypan blue stain. White scale bar shows 1 cm and black scale bar 600 Îźm. (EPS 23350 kb
Additional file 2: Figure S1. of A genetic framework for H2O2 induced cell death in Arabidopsis thaliana
No full textThe cat2 phenotype depends on sucrose concentration in the agar media. Ten days old seedlings in different sucrose concentrations (0, 0.5, 1 and 2 %). At 0 % sucrose the seedlings were bleached, with increased sucrose concentration the seedlings were green. (TIFF 2004 kb
Additional file 8: Figure S7. of A genetic framework for H2O2 induced cell death in Arabidopsis thaliana
No full textMaximum photosynthetic efficiency (Fv/Fm; mean±SE) in dark adapted plants after transfer to continuous light and restricted gas-exchange. Fourteen-days old seedlings were transferred from 70 μmol m−2 s−1 light intensity and 8h day/ 16h night to 120 μmol m−2 s−1 continuous light. Fv/Fm was measured on shift day, 2nd, 4th, and 7th. The experiment was repeated three times using 20 plants per repeat (n=60). Asterisks indicate significantly different Fv/Fm values of double mutant in time scale and compared to cat2 (p<0.05, General Linear Model). (EPS 815 kb
Additional file 1: Table S1. of A genetic framework for H2O2 induced cell death in Arabidopsis thaliana
No full textPrimers and restriction enzymes used for mutant genotyping. Additional information about the mutants used. (XLSX 14 kb
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