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Publikation

Anwer, M. U.; Davis, A.; Davis, S. J.; Quint, M.; Photoperiod sensing of the circadian clock is controlled by EARLY FLOWERING 3 and GIGANTEA Plant J. 101, 1397-1410, (2020) DOI: 10.1111/tpj.14604

ELF3 and GI are two important components of the Arabidopsis circadian clock. They are not only essential for the oscillator function but are also pivotal in mediating light inputs to the oscillator. Lack of either results in a defective oscillator causing severely compromised output pathways, such as photoperiodic flowering and hypocotyl elongation. Although single loss of function mutants of ELF3 and GI have been well‐studied, their genetic interaction remains unclear. We generated an elf3 gi double mutant to study their genetic relationship in clock‐controlled growth and phase transition phenotypes. We found that ELF3 and GI repress growth differentially during the night and the day, respectively. Circadian clock assays revealed that ELF3 and GI are essential Zeitnehmers that enable the oscillator to synchronize the endogenous cellular mechanisms to external environmental signals. In their absence, the circadian oscillator fails to synchronize to the light‐dark cycles even under diurnal conditions. Consequently, clock‐mediated photoperiod‐responsive growth and development are completely lost in plants lacking both genes, suggesting that ELF3 and GI together convey photoperiod sensing to the central oscillator. Since ELF3 and GI are conserved across flowering plants and represent important breeding and domestication targets, our data highlight the possibility of developing photoperiod‐insensitive crops by adjusting the allelic combination of these two key genes.
Publikation

Wasternack, C.; Termination in Jasmonate Signaling by MYC2 and MTBs Trends Plant Sci. 24, 667-669, (2019) DOI: 10.1016/j.tplants.2019.06.001

Jasmonic acid (JA) signaling can be switched off by metabolism of JA. The master regulator MYC2, interacting with MED25, has been shown to be deactivated by the bHLH transcription factors MTB1, MTB2, and MTB3. An autoregulatory negative feedback loop has been proposed for this termination in JA signaling.
Publikation

Wasternack, C.; New Light on Local and Systemic Wound Signaling Trends Plant Sci. 24, 102-105, (2019) DOI: 10.1016/j.tplants.2018.11.009

Electric signaling and Ca2+ waves were discussed to occur in systemic wound responses. Two new overlapping scenarios were identified: (i) membrane depolarization in two special cell types followed by an increase in systemic cytoplasmic Ca2+ concentration ([Ca2+]cyt), and (ii) glutamate sensed by GLUTAMATE RECEPTOR LIKE proteins and followed by Ca2+-based defense in distal leaves.
Publikation

Wasternack, C.; Hause, B.; A Bypass in Jasmonate Biosynthesis – the OPR3-independent Formation Trends Plant Sci. 23, 276-279, (2018) DOI: 10.1016/j.tplants.2018.02.011

For the first time in 25 years, a new pathway for biosynthesis of jasmonic acid (JA) has been identified. JA production takes place via 12-oxo-phytodienoic acid (OPDA) including reduction by OPDA reductases (OPRs). A loss-of-function allele, opr3-3, revealed an OPR3-independent pathway converting OPDA to JA.
Publikation

Grubb, C. D.; Zipp, B. J.; Kopycki, J.; Schubert, M.; Quint, M.; Lim, E.-K.; Bowles, D. J.; Pedras, M. S. C.; Abel, S.; Comparative analysis of Arabidopsis UGT74 glucosyltransferases reveals a special role of UGT74C1 in glucosinolate biosynthesis Plant J. 79, 92-105, (2014) DOI: 10.1111/tpj.12541

The study of glucosinolates and their regulation has provided a powerful framework for the exploration of fundamental questions about the function, evolution, and ecological significance of plant natural products, but uncertainties about their metabolism remain. Previous work has identified one thiohydroximate S‐glucosyltransferase, UGT74B1, with an important role in the core pathway, but also made clear that this enzyme functions redundantly and cannot be the sole UDP‐glucose dependent glucosyltransferase (UGT) in glucosinolate synthesis. Here, we present the results of a nearly comprehensive in vitro activity screen of recombinant Arabidopsis Family 1 UGTs, which implicate other members of the UGT74 clade as candidate glucosinolate biosynthetic enzymes. Systematic genetic analysis of this clade indicates that UGT74C1 plays a special role in the synthesis of aliphatic glucosinolates, a conclusion strongly supported by phylogenetic and gene expression analyses. Finally, the ability of UGT74C1 to complement phenotypes and chemotypes of the ugt74b1‐2 knockout mutant and to express thiohydroximate UGT activity in planta provides conclusive evidence for UGT74C1 being an accessory enzyme in glucosinolate biosynthesis with a potential function during plant adaptation to environmental challenge.
Publikation

Brandt, R.; Salla-Martret, M.; Bou-Torrent, J.; Musielak, T.; Stahl, M.; Lanz, C.; Ott, F.; Schmid, M.; Greb, T.; Schwarz, M.; Choi, S.-B.; Barton, M. K.; Reinhart, B. J.; Liu, T.; Quint, M.; Palauqui, J.-C.; Martínez-García, J. F.; Wenkel, S.; Genome-wide binding-site analysis of REVOLUTA reveals a link between leaf patterning and light-mediated growth responses Plant J. 72, 31-42, (2012) DOI: 10.1111/j.1365-313X.2012.05049.x

Unlike the situation in animals, the final morphology of the plant body is highly modulated by the environment. During Arabidopsis development, intrinsic factors provide the framework for basic patterning processes. CLASS III HOMEODOMAIN LEUCINE ZIPPER (HD‐ZIPIII) transcription factors are involved in embryo, shoot and root patterning. During vegetative growth HD‐ZIPIII proteins control several polarity set‐up processes such as in leaves and the vascular system. We have identified several direct target genes of the HD‐ZIPIII transcription factor REVOLUTA (REV) using a chromatin immunoprecipitation/DNA sequencing (ChIP‐Seq) approach. This analysis revealed that REV acts upstream of auxin biosynthesis and affects directly the expression of several class II HD‐ZIP transcription factors that have been shown to act in the shade‐avoidance response pathway. We show that, as well as involvement in basic patterning, HD‐ZIPIII transcription factors have a critical role in the control of the elongation growth that is induced when plants experience shade. Leaf polarity is established by the opposed actions of HD‐ZIPIII and KANADI transcription factors. Finally, our study reveals that the module that consists of HD‐ZIPIII/KANADI transcription factors controls shade growth antagonistically and that this antagonism is manifested in the opposed regulation of shared target genes.
Publikation

Delker, C.; Quint, M.; Expression level polymorphisms: heritable traits shaping natural variation Trends Plant Sci. 16, 481-488, (2011) DOI: 10.1016/j.tplants.2011.05.009

Natural accessions of many species harbor a wealth of genetic variation visible in a large array of phenotypes. Although expression level polymorphisms (ELPs) in several genes have been shown to contribute to variation in diverse traits, their general impact on adaptive variation has likely been underestimated. At present, ELPs have predominantly been correlated to quantitative trait loci (eQTLs) that occupy central hubs in signaling networks, which pleiotropically affect numerous traits. To increase the sensitivity of detecting minor effect eQTLs or those that act in a trait-specific manner, we emphasize the need for more systematic approaches. This requires, but is not limited to, refining experimental designs such as reduction of tissue complexity and combinatorial methods including a priori defined networks.
Publikation

Wasternack, C.; Kombrink, E.; Jasmonates: Structural Requirements for Lipid-Derived Signals Active in Plant Stress Responses and Development ACS Chem. Biol. 5, 63-77, (2010) DOI: 10.1021/cb900269u

Jasmonates are lipid-derived signals that mediate plant stress responses and development processes. Enzymes participating in biosynthesis of jasmonic acid (JA) (1, 2) and components of JA signaling have been extensively characterized by biochemical and molecular-genetic tools. Mutants of Arabidopsis and tomato have helped to define the pathway for synthesis of jasmonoyl-isoleucine (JA-Ile), the active form of JA, and to identify the F-box protein COI1 as central regulatory unit. However, details of the molecular mechanism of JA signaling have only recently been unraveled by the discovery of JAZ proteins that function in transcriptional repression. The emerging picture of JA perception and signaling cascade implies the SCFCOI1 complex operating as E3 ubiquitin ligase that upon binding of JA-Ile targets JAZ repressors for degradation by the 26S-proteasome pathway, thereby allowing the transcription factor MYC2 to activate gene expression. The fact that only one particular stereoisomer, (+)-7-iso-JA-l-Ile (4), shows high biological activity suggests that epimerization between active and inactive diastereomers could be a mechanism for turning JA signaling on or off. The recent demonstration that COI1 directly binds (+)-7-iso-JA-l-Ile (4) and thus functions as JA receptor revealed that formation of the ternary complex COI1-JA-Ile-JAZ is an ordered process. The pronounced differences in biological activity of JA stereoisomers also imply strict stereospecific control of product formation along the JA biosynthetic pathway. The pathway of JA biosynthesis has been unraveled, and most of the participating enzymes are well-characterized. For key enzymes of JA biosynthesis the crystal structures have been established, allowing insight into the mechanisms of catalysis and modes of substrate binding that lead to formation of stereospecific products.
Publikation

Quint, M.; Ito, H.; Zhang, W.; Gray, W. M.; Characterization of a novel temperature-sensitive allele of the CUL1/AXR6 subunit of SCF ubiquitin-ligases Plant J. 43, 371-383, (2005) DOI: 10.1111/j.1365-313X.2005.02449.x

Selective protein degradation by the ubiquitin‐proteasome pathway has emerged as a key regulatory mechanism in a wide variety of cellular processes. The selective components of this pathway are the E3 ubiquitin‐ligases which act downstream of the ubiquitin‐activating and ‐conjugating enzymes to identify specific substrates for ubiquitinylation. SCF‐type ubiquitin‐ligases are the most abundant class of E3 enzymes in Arabidopsis. In a genetic screen for enhancers of the tir1‐1 auxin response defect, we identified eta1 /axr6‐3 , a recessive and temperature‐sensitive mutation in the CUL1 core component of the SCFTIR1 complex. The axr6‐3 mutation interferes with Skp1 binding, thus preventing SCF complex assembly. axr6‐3 displays a pleiotropic phenotype with defects in numerous SCF‐regulated pathways including auxin signaling, jasmonate signaling, flower development, and photomorphogenesis. We used axr6‐3 as a tool for identifying pathways likely to be regulated by SCF‐mediated proteolysis and propose new roles for SCF regulation of the far‐red light/phyA and sugar signaling pathways. The recessive inheritance and the temperature‐sensitive nature of the pleiotropically acting axr6‐3 mutation opens promising possibilities for the identification and investigation of SCF‐regulated pathways in Arabidopsis.
Publikation

Stenzel, I.; Hause, B.; Maucher, H.; Pitzschke, A.; Miersch, O.; Ziegler, J.; Ryan, C. A.; Wasternack, C.; Allene oxide cyclase dependence of the wound response and vascular bundle-specific generation of jasmonates in tomato - amplification in wound signalling Plant J. 33, 577-589, (2003) DOI: 10.1046/j.1365-313X.2003.01647.x

The allene oxide cyclase (AOC)‐catalyzed step in jasmonate (JA) biosynthesis is important in the wound response of tomato. As shown by treatments with systemin and its inactive analog, and by analysis of 35S::prosysteminsense and 35S::prosysteminantisense plants, the AOC seems to be activated by systemin (and JA) leading to elevated formation of JA. Data are presented on the local wound response following activation of AOC and generation of JA, both in vascular bundles. The tissue‐specific occurrence of AOC protein and generation of JA is kept upon wounding or other stresses, but is compromised in 35S::AOCsense plants, whereas 35S::AOCantisense plants exhibited residual AOC expression, a less than 10% rise in JA, and no detectable expression of wound response genes. The (i) activation of systemin‐dependent AOC and JA biosynthesis occurring only upon substrate generation, (ii) the tissue‐specific occurrence of AOC in vascular bundles, where the prosystemin gene is expressed, and (iii) the tissue‐specific generation of JA suggest an amplification in the wound response of tomato leaves allowing local and rapid defense responses.
  • Die Leibniz-Gemeinschaft
  • Digitalisierung in der Landwirtschaft
  • Martin-Luther Universität Halle
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