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Publikation

Raschke, A.; Ibañez, C.; Ullrich, K. K.; Anwer, M. U.; Becker, S.; Glöckner, A.; Trenner, J.; Denk, K.; Saal, B.; Sun, X.; Ni, M.; Davis, S. J.; Delker, C.; Quint, M.; Natural variants of ELF3 affect thermomorphogenesis by transcriptionally modulating PIF4-dependent auxin response genes BMC Plant Biol. 15, 197, (2015) DOI: 10.1186/s12870-015-0566-6

BackgroundPerception and transduction of temperature changes result in altered growth enabling plants to adapt to increased ambient temperature. While PHYTOCHROME-INTERACTING FACTOR4 (PIF4) has been identified as a major ambient temperature signaling hub, its upstream regulation seems complex and is poorly understood. Here, we exploited natural variation for thermo-responsive growth in Arabidopsis thaliana using quantitative trait locus (QTL) analysis.ResultsWe identified GIRAFFE2.1, a major QTL explaining ~18 % of the phenotypic variation for temperature-induced hypocotyl elongation in the Bay-0 x Sha recombinant inbred line population. Transgenic complementation demonstrated that allelic variation in the circadian clock regulator EARLY FLOWERING3 (ELF3) is underlying this QTL. The source of variation could be allocated to a single nucleotide polymorphism in the ELF3 coding region, resulting in differential expression of PIF4 and its target genes, likely causing the observed natural variation in thermo-responsive growth.ConclusionsIn combination with other recent studies, this work establishes the role of ELF3 in the ambient temperature signaling network. Natural variation of ELF3-mediated gating of PIF4 expression during nightly growing periods seems to be affected by a coding sequence quantitative trait nucleotide that confers a selective advantage in certain environments. In addition, natural ELF3 alleles seem to differentially integrate temperature and photoperiod information to induce architectural changes. Thus, ELF3 emerges as an essential coordinator of growth and development in response to diverse environmental cues and implicates ELF3 as an important target of adaptation.
Preprints

Raschke, A.; Ibañez, C.; Ullrich, K. K.; Anwer, M. U.; Becker, S.; Glöckner, A.; Trenner, J.; Denk, K.; Saal, B.; Sun, X.; Ni, M.; Davis, S. J.; Delker, C.; Quint, M.; Natural Variants of ELF3 Affect Thermomorphogenesis by Transcriptionally Modulating PIF4-Dependent Auxin Response Genes bioRxiv (2015) DOI: 10.1101/015305

Perception and transduction of temperature changes result in altered growth enabling plants to adapt to increased ambient temperature. While PHYTOCHROME-INTERACTING FACTOR4 (PIF4) has been identified as a major ambient temperature signaling hub, its upstream regulation seems complex and is poorly understood. Here, we exploited natural variation for thermo-responsive growth in Arabidopsis thaliana using quantitative trait locus (QTL) analysis. We identified GIRAFFE2.1, a major QTL explaining ~18% of the phenotypic variation for temperature-induced hypocotyl elongation in the Bay-0 x Sha recombinant inbred line population. Transgenic complementation demonstrated that allelic variation in the circadian clock regulator EARLY FLOWERING3 (ELF3) is underlying this QTL. The source of variation could be allocated to a single nucleotide polymorphism in the ELF3 coding region, resulting in differential expression of PIF4 and its target genes, likely causing the observed natural variation in thermo-responsive growth. In combination with other recent studies, this work establishes the role of ELF3 in the ambient temperature signaling network. Natural variation of ELF3-mediated gating of PIF4 expression during nightly growing periods seems to be affected by a coding sequence quantitative trait nucleotide that confers a selective advantage in certain environments. In addition, natural ELF3 alleles seem to differentially integrate temperature and photoperiod cues to induce architectural changes. Thus, ELF3 emerges as an essential coordinator of growth and development in response to diverse environmental cues and implicates ELF3 as an important target of adaptation.
Publikation

Delker, C.; Pöschl, Y.; Raschke, A.; Ullrich, K.; Ettingshausen, S.; Hauptmann, V.; Grosse, I.; Quint, M.; Natural Variation of Transcriptional Auxin Response Networks in Arabidopsis thaliana Plant Cell 22, 2184-2200, (2010) DOI: 10.1105/tpc.110.073957

Natural variation has been observed for various traits in Arabidopsis thaliana. Here, we investigated natural variation in the context of physiological and transcriptional responses to the phytohormone auxin, a key regulator of plant development. A survey of the general extent of natural variation to auxin stimuli revealed significant physiological variation among 20 genetically diverse natural accessions. Moreover, we observed dramatic variation on the global transcriptome level after induction of auxin responses in seven accessions. Although we detect isolated cases of major-effect polymorphisms, sequencing of signaling genes revealed sequence conservation, making selective pressures that favor functionally different protein variants among accessions unlikely. However, coexpression analyses of a priori defined auxin signaling networks identified variations in the transcriptional equilibrium of signaling components. In agreement with this, cluster analyses of genome-wide expression profiles followed by analyses of a posteriori defined gene networks revealed accession-specific auxin responses. We hypothesize that quantitative distortions in the ratios of interacting signaling components contribute to the detected transcriptional variation, resulting in physiological variation of auxin responses among accessions.
Publikation

Delker, C.; Raschke, A.; Quint, M.; Auxin dynamics: the dazzling complexity of a small molecule’s message Planta 227, 929-941, (2008) DOI: 10.1007/s00425-008-0710-8

The phytohormone auxin is a potent regulator of plant development. Since its discovery in the beginning of the twentieth century many aspects of auxin biology have been extensively studied, ranging from biosynthesis and metabolism to the elucidation of molecular components of downstream signaling. With the identification of the F-box protein TIR1 as an auxin receptor a major breakthrough in understanding auxin signaling has been achieved and recent modeling approaches have shed light on the putative mechanisms underlying the establishment of auxin gradients and maxima essential for many auxin-regulated processes. Here, we review these and other recent advances in unraveling the entanglement of biosynthesis, polar transport and cellular signaling events that allow small auxinic molecules to facilitate their complex regulatory action.
Publikation

Danon, A.; Miersch, O.; Felix, G.; op den Camp, R. G. L.; Apel, K.; Concurrent activation of cell death-regulating signaling pathways by singlet oxygen in Arabidopsis thaliana Plant J. 41, 68-80, (2005) DOI: 10.1111/j.1365-313X.2004.02276.x

Upon a dark/light shift the conditional flu mutant of Arabidopsis starts to generate singlet oxygen (1O2), a non‐radical reactive oxygen species that is restricted to the plastid compartment. Immediately after the shift, plants stop growing and develop necrotic lesions. We have established a protoplast system, which allows detection and characterization of the death response in flu induced by the release of 1O2. Vitamin B6 that quenches 1O2 in fungi was able to protect flu protoplasts from cell death. Blocking ethylene production was sufficient to partially inhibit the death reaction. Similarly, flu mutant seedlings expressing transgenic NahG were partially protected from the death provoked by the release of 1O2, indicating a requirement for salicylic acid (SA) in this process, whereas in cells depleted of both, ethylene and SA, the extent of cell death was reduced to the wild‐type level. The flu mutant was also crossed with the jasmonic acid (JA)‐depleted mutant opr3 , and with the JA, OPDA and dinor OPDA (dnOPDA)‐depleted dde2‐2 mutant. Analysis of the resulting double mutants revealed that in contrast to the JA‐induced suppression of H2O2/superoxide‐dependent cell death reported earlier, JA promotes singlet oxygen‐mediated cell death in flu , whereas other oxylipins such as OPDA and dnOPDA antagonize this death‐inducing activity of JA.
Publikation

Nibbe, M.; Hilpert, B.; Wasternack, C.; Miersch, O.; Apel, K.; Cell death and salicylate- and jasmonate-dependent stress responses in Arabidopsis are controlled by single cet genes Planta 216, 120-128, (2002) DOI: 10.1007/s00425-002-0907-1

The jasmonic acid (JA)-dependent regulation of the Thi2.1 gene had previously been exploited for setting up a genetic screen for the isolation of signal transduction mutants of Arabidopsis thaliana (L.) Heynh. that constitutively express the thionin gene. Several cet mutants had been isolated which showed a constitutive expression of the thionin gene. These cet mutants, except for one, also showed spontaneous leaf cell necrosis and were up-regulated in the expression of the PR1 gene, reactions often associated with the systemic acquired resistance (SAR) pathway. Four of these cet mutants, cet1, cet2, cet3 and cet4.1 were crossed with the fad triple and coi1 mutants that are blocked at two steps within the JA-dependent signaling pathway, and with transgenic NahG plants that are deficient in salicylic acid (SA) and are unable to activate SAR. Analysis of the various double-mutant lines revealed that the four cet genes act within a signaling cascade at or prior to branch points from which not only JA-dependent signals but also SA-dependent signaling and cell death pathways diverge.
Publikation

Hilpert, B.; Bohlmann, H.; Den Camp, R. o.; Przybyla, D.; Miersch, O.; Buchala, A.; Apel, K.; Isolation and characterization of signal transduction mutants of Arabidopsis thaliana that constitutively activate the octadecanoid pathway and form necrotic microlesions Plant J. 26, 435-446, (2001) DOI: 10.1046/j.1365-313X.2001.2641036.x

Thionins are a group of antimicrobial polypeptides that form part of the plant's defense mechanism against pathogens. The Thi 2.1 thionin gene of Arabidopsis thaliana has been shown to be inducible by jasmonic acid (JA), an oxylipin‐like hormone derived from oxygenated linolenic acid and synthesized via the octadecanoid pathway. The JA‐dependent regulation of the Thi 2.1 gene has been exploited for setting up a genetic screen for the isolation of signal transduction mutants that constitutively express the Thi 2.1 gene. Ten cet‐mutants have been isolated which showed a c onstitutive e xpression of the t hionin gene. Allelism tests revealed that they represent at least five different loci. Some mutants are dominant, others recessive, but all cet mutations behaved as monogenic traits when backcrossed with Thi 2.1‐GUS plants. Some of the mutants overproduce JA and its bioactive precursor 12‐oxophytodienoic acid (OPDA) up to 40‐fold while others have the same low levels as the control wildtype plants. Two of the mutants showed a strong induction of both the salicylic acid (SA)‐ and the JA‐dependent signaling pathways, while the majority seems to be affected only in the octadecanoid pathway. The Thi 2.1 thionin gene and the Pdf 1.2 defensin gene are activated independently, though both are regulated by JA. The cet‐mutants, except for one, also show a spontaneous leaf cell necrosis, a reaction often associated with the systemic acquired resistance (SAR) pathway.
Publikation

Bohlmann, H.; Vignutelli, A.; Hilpert, B.; Miersch, O.; Wasternack, C.; Apel, K.; Wounding and chemicals induce expression of the Arabidopsis thaliana gene Thi2.1, encoding a fungal defense thionin, via the octadecanoid pathway FEBS Lett. 437, 281-286, (1998) DOI: 10.1016/S0014-5793(98)01251-4

In seedlings of Arabidopsis thaliana the thionin gene Thi2.1 is inducible by methyl jasmonate, wounding, silver nitrate, coronatine, and sorbitol. We have used a biochemical and genetic approach to test the signal transduction of these different inducers. Both exogenously applied jasmonates and jasmonates produced endogenously upon stress induction, lead to GUS expression in a Thi2.1 promoter-uidA transgenic line. No GUS expression was observed in a coi1 mutant background which lacks jasmonate perception whereas methyl jasmonate and coronatine but not the other inducers were able to overcome the block in jasmonic acid production in a fad3-2 fad7-2 fad8 mutant background. Our results show conclusively that all these inducers regulate Thi2-1 gene expression via the octadecanoid pathway.
Publikation

Vignutelli, A.; Wasternack, C.; Apel, K.; Bohlmann, H.; Systemic and local induction of an Arabidopsis thionin gene by wounding and pathogens Plant J. 14, 285-295, (1998) DOI: 10.1046/j.1365-313X.1998.00117.x

The Arabidopsis Thi2.1 thionin gene was cloned and sequenced. The promoter was fused to the uidA gene and stably transformed into Arabidopsis to study its regulation. GUS expression levels correlated with the steady‐state levels of Thi2.1 mRNA, thus demonstrating that the promoter is sufficient for the regulation of the Thi2.1 gene. The sensitivity of the Thi2.1 gene to methyl jasmonate was found to be developmentally determined. Systemic and local expression could be induced by wounding and inoculation with Fusarium oxysporum f sp. matthiolae . A deletion analysis of the promoter identified a fragment of 325 bp upstream of the start codon, which appears to contain all the elements necessary for the regulation of the Thi2.1 gene. These results support the view that thionins are defence proteins, and indicate the possibility that resistance of Arabidopsis plants to necrotrophic fungal pathogens is mediated through the octadecanoid pathway.
  • Die Leibniz-Gemeinschaft
  • Digitalisierung in der Landwirtschaft
  • Martin-Luther Universität Halle
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