Publikation
Chutia, R.; Abel, S.; Ziegler, J. Iron and Phosphate Deficiency Regulators
Concertedly Control Coumarin Profiles in Arabidopsis thaliana Roots
During Iron, Phosphate, and Combined Deficiencies Front Plant Sci 10, 113, (2019) DOI: 10.3389/fpls.2019.00113
Plants face varying nutrient conditions, to which
they have to adapt to. Adaptive responses are nutrient-specific and
strategies to ensure supply and homeostasis for one nutrient might be
opposite to another one, as shown for phosphate (Pi) and iron (Fe)
deficiency responses, where many genes are regulated in an opposing
manner. This was also observed on the metabolite levels. Whereas root
and exudate levels of catechol-type coumarins, phenylpropanoid-derived
2-benzopyranones, which facilitate Fe acquisition, are elevated after Fe
deficiency, they are decreased after Pi deficiency. Exposing plants to
combined Pi and Fe deficiency showed that the generation of coumarin
profiles in Arabidopsis thaliana roots by Pi deficiency considerably
depends on the availability of Fe. Similarly, the effect of Fe
deficiency on coumarin profiles is different at low compared to high Pi
availability. These findings suggest a fine-tuning of coumarin profiles,
which depends on Fe and Pi availability. T-DNA insertion lines
exhibiting aberrant expression of genes involved in the regulation of Pi
starvation responses (PHO1, PHR1, bHLH32, PHL1, SPX1) and Fe starvation
responses (BRUTUS, PYE, bHLH104, FIT) were used to analyze the
regulation of the generation of coumarin profiles in Arabidopsis
thaliana roots by Pi, Fe, and combined Pi and Fe deficiency. The
analysis revealed a role of several Fe-deficiency response regulators in
the regulation of Fe and of Pi deficiency-induced coumarin profiles as
well as for Pi deficiency response regulators in the regulation of Pi
and of Fe deficiency-induced coumarin profiles. Additionally, the
regulation of Fe deficiency-induced coumarin profiles by Fe deficiency
response regulators is influenced by Pi availability. Conversely,
regulation of Pi deficiency-induced coumarin profiles by Pi deficiency
response regulators is modified by Fe availability.
Publikation
Janitza, P.; Ullrich, K. K.; Quint, M. Toward a comprehensive phylogenetic reconstruction
of the evolutionary history of mitogen-activated protein kinases in the
plant kingdom Front Plant Sci 3, 271, (2012) DOI: 10.3389/fpls.2012.00271
The mitogen-activated protein kinase (MAPK)
pathway is a three-tier signaling cascade that transmits cellular
information from the plasma membrane to the cytoplasm where it triggers
downstream responses. The MAPKs represent the last step in this cascade
and are activated when both tyrosine and threonine residues in a
conserved TxY motif are phosphorylated by MAPK kinases, which in turn
are themselves activated by phosphorylation by MAPK kinase kinases. To
understand the molecular evolution of MAPKs in the plant kingdom, we
systematically conducted a Hidden-Markov-Model based screen to identify
MAPKs in 13 completely sequenced plant genomes. In this analysis, we
included green algae, bryophytes, lycophytes, and several mono- and
eudicotyledonous species covering >800 million years of evolution.
The phylogenetic relationships of the 204 identified MAPKs based on
Bayesian inference facilitated the retraction of the sequence of
emergence of the four major clades that are characterized by the
presence of a TDY or TEY-A/TEY-B/TEY-C type kinase activation loop. We
present evidence that after the split of TDY- and TEY-type MAPKs,
initially the TEY-C clade emerged. This was followed by the TEY-B clade
in early land plants until the TEY-A clade finally emerged in flowering
plants. In addition to these well characterized clades, we identified
another highly conserved clade of 45 MAPK-likes, members of which were
previously described as Mak-homologous kinases. In agreement with their
essential functions, molecular population genetic analysis of MAPK genes
in Arabidopsis thaliana accessions reveal that purifying selection
drove the evolution of the MAPK family, implying strong functional
constraints on MAPK genes. Closely related MAPKs most likely
subfunctionalized, a process in which differential transcriptional
regulation of duplicates may be involved.
Publikation
Fellenberg, C.; Ziegler, J.; Handrick, V.; Vogt, T. Polyamine homeostasis in wild type and phenolamide deficient Arabidopsis thaliana stamens Front Plant Sci 3, 180, (2012) DOI: 10.3389/fpls.2012.00180
Polyamines (PAs) like putrescine, spermidine, and spermine are ubiquitous polycationic molecules that occur in all living cells and have a role in a wide variety of biological processes. High amounts of spermidine conjugated to hydroxycinnamic acids are detected in the tryphine of Arabidopsis thaliana pollen grains. Tapetum localized spermidine hydroxycinnamic acid transferase (SHT) is essential for the biosynthesis of these anther specific tris-conjugated spermidine derivatives. Sht knockout lines show a strong reduction of hydroxycinnamic acid amides (HCAAs). The effect of HCAA-deficient anthers on the level of free PAs was measured by a new sensitive and reproducible method using 9-fluorenylmethyl chloroformate (FMOC) and fluorescence detection by HPLC. PA concentrations can be accurately determined even when very limited amounts of plant material, as in the case of A. thaliana stamens, are available. Analysis of free PAs in wild type stamens compared to sht deficient mutants and transcript levels of key PA biosynthetic genes revealed a highly controlled regulation of PA homeostasis in A. thaliana anthers.
Publikation
Stenzel, I.; Ischebeck, T.; Quint, M.; Heilmann, I. Variable regions of PI4P 5-kinases direct PtdIns(4,5)P2 toward alternative regulatory functions in tobacco pollen tubes Front Plant Sci 2, 114, (2012) DOI: 10.3389/fpls.2011.00114
The apical plasma membrane of pollen tubes contains different PI4P 5-kinases that all produce phosphatidylinositol-4,5-bisphosphate [PtdIns(4,5)P2] but exert distinct cellular effects. In the present example, overexpression of Arabidopsis AtPIP5K5 or tobacco NtPIP5K6-1 caused growth defects previously attributed to increased pectin secretion. In contrast, overexpression of Arabidopsis AtPIP5K2 caused apical tip swelling implicated in altering actin fine structure in the pollen tube apex. AtPIP5K5, NtPIP5K6-1, and AtPIP5K2 share identical domain structures. Domains required for correct membrane association of the enzymes were identified by systematic deletion of N-terminal domains and subsequent expression of fluorescence-tagged enzyme truncations in tobacco pollen tubes. A variable linker region (Lin) contained in all PI4P 5-kinase isoforms of subfamily B, but not conserved in sequence, was recognized to be necessary for correct subcellular localization of AtPIP5K5, NtPIP5K6-1, and AtPIP5K2. Deletion of N-terminal domains including the Lin domain did not impair catalytic activity of recombinant AtPIP5K5, NtPIP5K6-1, or AtPIP5K2 in vitro; however, the presence of the Lin domain was necessary for in vivo effects on pollen tube growth upon overexpression of truncated enzymes. Overexpression of catalytically inactive variants of AtPIP5K5, NtPIP5K6-1, or AtPIP5K2 did not influence pollen tube growth, indicating that PtdIns(4,5)P2 production rather than structural properties of PI4P 5-kinases was relevant for the manifestation of growth phenotypes. When Lin domains were swapped between NtPIP5K6-1 and AtPIP5K2 and the chimeric enzymes overexpressed in pollen tubes, the chimeras reciprocally gained the capabilities to invoke tip swelling or secretion phenotypes, respectively. The data indicate that the Lin domain directed the enzymes into different regulatory contexts, possibly contributing to channeling of PtdIns(4,5)P2 at the interface of secretion and actin cytoskeleton.
Publikation
Phosphate (Pi) and its anhydrides constitute
major nodes in metabolism. Thus, plant performance depends directly on
Pi nutrition. Inadequate Pi availability in the rhizosphere is a common
challenge to plants, which activate metabolic and developmental
responses to maximize Pi usage and acquisition. The sensory mechanisms
that monitor environmental Pi and transmit the nutritional signal to
adjust root development have increasingly come into focus. Recent
transcriptomic analyses and genetic approaches have highlighted complex
antagonistic interactions between external Pi and Fe bioavailability and
have implicated the stem cell niche as a target of Pi sensing to
regulate root meristem activity.
Publikation
Auxin regulates a host of plant developmental and physiological processes, including embryogenesis, vascular differentiation, organogenesis, tropic growth, and root and shoot architecture. Genetic and biochemical studies carried out over the past decade have revealed that much of this regulation involves the SCFTIR1/AFB-mediated proteolysis of the Aux/IAA family of transcriptional regulators. With the recent finding that the TRANSPORT INHIBITOR RESPONSE1 (TIR1)/AUXIN SIGNALING F-BOX (AFB) proteins also function as auxin receptors, a potentially complete, and surprisingly simple, signaling pathway from perception to transcriptional response is now before us. However, understanding how this seemingly simple pathway controls the myriad of specific auxin responses remains a daunting challenge, and compelling evidence exists for SCFTIR1/AFB-independent auxin signaling pathways.
Publikation
Wasternack, C.; Stenzel, I.; Hause, B.; Hause, G.; Kutter, C.; Maucher, H.; Neumerkel, J.; Feussner, I.; Miersch, O. The wound response in tomato - Role of jasmonic acid J. Plant Physiol 163, 297-306 , (2006) DOI: 10.1016/j.jplph.2005.10.014
0
Publikation
Sharma, V.K.; Monostori, T.; Hause, B.; Maucher, H.; Göbel, C.; Hornung, E.; Hänsch, R.; Bittner, F.; Wasternack, C.; Feussner, I.; Mendel, R.R.; Schulze, J. Genetic transformation of barley to modify expression of a 13-lipoxygenase Acta Biol. Szeged 49, 33-34 , (2005)
Immature scutella of barley were transformed with cDNA coding for a 13-li-poxygenase of barley (LOX-100) via particle bombardment. Regenerated plants were tested by PAT-assay, Western-analysis and PCR-screening. Immunocytochemical assay of T0 plants showed expression of the LOX cDNA both in the chloroplasts and in the cytosol, depending on the presence of the chloroplast signal peptide sequences in the cDNA. A few transgenic plants containing higher amounts of LOX-derived products have been found. These are the candidates for further analysis concerning pathogen resistance.