Publikation
Mitra, D.; Klemm, S.; Kumari, P.; Quegwer, J.; Möller, B.; Poeschl, Y.; Pflug, P.; Stamm, G.; Abel, S.; Bürstenbinder, K. Microtubule-associated protein IQ67 DOMAIN5 regulates morphogenesis of leaf pavement cells in Arabidopsis thaliana J Exp Bot 70, 529-543, (2019) DOI: 10.1093/jxb/ery395
Plant microtubules form a highly dynamic
intracellular network with important roles for regulating cell division,
cell proliferation and cell morphology. Its organization and dynamics
are coordinated by various microtubule-associated proteins (MAPs) that
integrate environmental and developmental stimuli to fine-tune and
adjust cytoskeletal arrays. IQ67 DOMAIN (IQD) proteins recently emerged
as a class of plant-specific MAPs with largely unknown functions. Here,
using a reverse genetics approach, we characterize Arabidopsis IQD5 in
terms of its expression domains, subcellular localization and biological
functions. We show that IQD5 is expressed mostly in vegetative tissues,
where it localizes to cortical microtubule arrays. Our phenotypic
analysis of iqd5 loss-of-function lines reveals functions of IQD5 in
pavement cell (PC) shape morphogenesis. Histochemical analysis of cell
wall composition further suggests reduced rates of cellulose deposition
in anticlinal cell walls, which correlate with reduced anisotropic
expansion. Lastly, we demonstrate IQD5-dependent recruitment of
calmodulin calcium sensors to cortical microtubule arrays and provide
first evidence for important roles of calcium in regulation of PC
morphogenesis. Our work thus identifies IQD5 as a novel player in PC
shape regulation, and, for the first time, links calcium signaling to
developmental processes that regulate anisotropic growth in PCs.
Publikation
Kölling, M.; Kumari, P.; Bürstenbinder, K. Calcium- and calmodulin-regulated
microtubule-associated proteins as signal-integration hubs at the plasma
membrane–cytoskeleton nexus J Exp Bot 70, 387-396, (2019) DOI: 10.1093/jxb/ery397
Plant growth and development are a genetically
predetermined series of events but can change dramatically in response
to environmental stimuli, involving perpetual pattern formation and
reprogramming of development. The rate of growth is determined by cell
division and subsequent cell expansion, which are restricted and
controlled by the cell wall–plasma membrane–cytoskeleton continuum, and
are coordinated by intricate networks that facilitate intra- and
intercellular communication. An essential role in cellular signaling is
played by calcium ions, which act as universal second messengers that
transduce, integrate, and multiply incoming signals during numerous
plant growth processes, in part by regulation of the microtubule
cytoskeleton. In this review, we highlight recent advances in the
understanding of calcium-mediated regulation of microtubule-associated
proteins, their function at the microtubule cytoskeleton, and their
potential role as hubs in crosstalk with other signaling pathways.
Publikation
Ibañez, C.; Poeschl, Y.; Peterson, T.; Bellstädt, J.; Denk, K.; Gogol-Döring, A.; Quint, M.; Delker, C. Ambient temperature and genotype differentially affect developmental and phenotypic plasticity in Arabidopsis thaliana BMC Plant Biol 17, 114, (2017) DOI: 10.1186/s12870-017-1068-5
BackgroundGlobal increase in ambient temperatures
constitute a significant challenge to wild and cultivated plant species.
Forward genetic analyses of individual temperature-responsive traits
have resulted in the identification of several signaling and response
components. However, a comprehensive knowledge about temperature
sensitivity of different developmental stages and the contribution of
natural variation is still scarce and fragmented at best.ResultsHere, we
systematically analyze thermomorphogenesis throughout a complete life
cycle in ten natural Arabidopsis thaliana accessions grown under long
day conditions in four different temperatures ranging from 16 to 28 °C.
We used Q10, GxE, phenotypic divergence and correlation analyses to
assess temperature sensitivity and genotype effects of more than 30
morphometric and developmental traits representing five phenotype
classes. We found that genotype and temperature differentially affected
plant growth and development with variing strengths. Furthermore,
overall correlations among phenotypic temperature responses was
relatively low which seems to be caused by differential capacities for
temperature adaptations of individual
accessions.ConclusionGenotype-specific temperature responses may be
attractive targets for future forward genetic approaches and
accession-specific thermomorphogenesis maps may aid the assessment of
functional relevance of known and novel regulatory components.
Publikation
Wasternack, C.; Song, S. Jasmonates: biosynthesis, metabolism, and signaling by proteins activating and repressing transciption J Exp Bot 68, 1303-1321, (2017) DOI: 10.1093/jxb/erw443
The lipid-derived phytohormone jasmonate (JA) regulates plant growth, development, secondary metabolism, defense against insect attack and pathogen infection, and tolerance to abiotic stresses such as wounding, UV light, salt, and drought. JA was first identified in 1962, and since the 1980s many studies have analyzed the physiological functions, biosynthesis, distribution, metabolism, perception, signaling, and crosstalk of JA, greatly expanding our knowledge of the hormone’s action. In response to fluctuating environmental cues and transient endogenous signals, the occurrence of multilayered organization of biosynthesis and inactivation of JA, and activation and repression of the COI1–JAZ-based perception and signaling contributes to the fine-tuning of JA responses. This review describes the JA biosynthetic enzymes in terms of gene families, enzymatic activity, location and regulation, substrate specificity and products, the metabolic pathways in converting JA to activate or inactivate compounds, JA signaling in perception, and the co-existence of signaling activators and repressors
Publikation
Trenner, J.; Poeschl, Y.; Grau, J.; Gogol-Döring, A.; Quint, M.; Delker, C. Auxin-induced expression divergence between Arabidopsis species may originate within the TIR1/AFB–AUX/IAA–ARF module J Exp Bot 68, 539-552, (2017) DOI: 10.1093/jxb/erw457
Auxin is an essential regulator of plant growth and development, and auxin signaling components are conserved among land plants. Yet, a remarkable degree of natural variation in physiological and transcriptional auxin responses has been described among Arabidopsis thaliana accessions. As intraspecies comparisons offer only limited genetic variation, we here inspect the variation of auxin responses between A. thaliana and A. lyrata. This approach allowed the identification of conserved auxin response genes including novel genes with potential relevance for auxin biology. Furthermore, promoter divergences were analyzed for putative sources of variation. De novo motif discovery identified novel and variants of known elements with potential relevance for auxin responses, emphasizing the complex, and yet elusive, code of element combinations accounting for the diversity in transcriptional auxin responses. Furthermore, network analysis revealed correlations of interspecies differences in the expression of AUX/IAA gene clusters and classic auxin-related genes. We conclude that variation in general transcriptional and physiological auxin responses may originate substantially from functional or transcriptional variations in the TIR1/AFB, AUX/IAA, and ARF signaling network. In that respect, AUX/IAA gene expression divergence potentially reflects differences in the manner in which different species transduce identical auxin signals into gene expression responses.
Publikation
Ziegler, J.; Schmidt, S.; Chutia, R.; Müller, J.; Böttcher, C.; Strehmel, N.; Scheel, D.; Abel, S. Non-targeted profiling of semi-polar metabolites
in Arabidopsis root exudates uncovers a role for coumarin secretion and
lignification during the local response to phosphate limitation J Exp Bot 67, 1421-1432, (2016) DOI: 10.1093/jxb/erv539
Plants have evolved two major strategies to cope with phosphate (Pi) limitation. The systemic response, mainly comprising increased Pi uptake and metabolic adjustments for more efficient Pi use, and the local response, enabling plants to explore Pi-rich soil patches by reorganization of the root system architecture. Unlike previous reports, this study focused on root exudation controlled by the local response to Pi deficiency. To approach this, a hydroponic system separating the local and systemic responses was developed. Arabidopsis thaliana genotypes exhibiting distinct sensitivities to Pi deficiency could be clearly distinguished by their root exudate composition as determined by non-targeted reversed-phase ultraperformance liquid chromatography electrospray ionization quadrupole-time-of-flight mass spectrometry metabolite profiling. Compared with wild-type plants or insensitive low phosphate root 1 and 2 (lpr1 lpr2) double mutant plants, the hypersensitive phosphate deficiency response 2 (pdr2) mutant exhibited a reduced number of differential features in root exudates after Pi starvation, suggesting the involvement of PDR2-encoded P5-type ATPase in root exudation. Identification and analysis of coumarins revealed common and antagonistic regulatory pathways between Pi and Fe deficiency-induced coumarin secretion. The accumulation of oligolignols in root exudates after Pi deficiency was inversely correlated with Pi starvation-induced lignification at the root tips. The strongest oligolignol accumulation in root exudates was observed for the insensitive lpr1 lpr2 double mutant, which was accompanied by the absence of Pi deficiency-induced lignin deposition, suggesting a role of LPR ferroxidases in lignin polymerization during Pi starvation.
Publikation
Hoehenwarter, W.; Mönchgesang, S.; Neumann, S.; Majovsky, P.; Abel, S.; Müller, J. Comparative expression profiling reveals a role of the root apoplast in local phosphate response BMC Plant Biol 16 , 106, (2016) DOI: 10.1186/s12870-016-0790-8
BackgroundPlant adaptation to limited phosphate availability
comprises a wide range of responses to conserve and remobilize internal
phosphate sources and to enhance phosphate acquisition. Vigorous
restructuring of root system architecture provides a developmental
strategy for topsoil exploration and phosphate scavenging. Changes in
external phosphate availability are locally sensed at root tips and
adjust root growth by modulating cell expansion and cell division. The
functionally interacting Arabidopsis genes, LOW PHOSPHATE RESPONSE 1 and
2 (LPR1/LPR2) and PHOSPHATE DEFICIENCY RESPONSE 2 (PDR2), are key
components of root phosphate sensing. We recently demonstrated that the
LOW PHOSPHATE RESPONSE 1 - PHOSPHATE DEFICIENCY RESPONSE 2 (LPR1-PDR2)
module mediates apoplastic deposition of ferric iron (Fe3+) in the
growing root tip during phosphate limitation. Iron deposition coincides
with sites of reactive oxygen species generation and triggers cell wall
thickening and callose accumulation, which interfere with cell-to-cell
communication and inhibit root growth.ResultsWe took advantage of
the opposite phosphate-conditional root phenotype of the phosphate
deficiency response 2 mutant (hypersensitive) and low phosphate response
1 and 2 double mutant (insensitive) to investigate the phosphate
dependent regulation of gene and protein expression in roots using
genome-wide transcriptome and proteome analysis. We observed an
overrepresentation of genes and proteins that are involved in the
regulation of iron homeostasis, cell wall remodeling and reactive oxygen
species formation, and we highlight a number of candidate genes with a
potential function in root adaptation to limited phosphate availability.
Our experiments reveal that FERRIC REDUCTASE DEFECTIVE 3 mediated,
apoplastic iron redistribution, but not intracellular iron uptake and
iron storage, triggers phosphate-dependent root growth modulation. We
further highlight expressional changes of several cell wall-modifying
enzymes and provide evidence for adjustment of the pectin network at
sites of iron accumulation in the root.ConclusionOur study
reveals new aspects of the elaborate interplay between phosphate
starvation responses and changes in iron homeostasis. The results
emphasize the importance of apoplastic iron redistribution to mediate
phosphate-dependent root growth adjustment and suggest an important role
for citrate in phosphate-dependent apoplastic iron transport. We
further demonstrate that root growth modulation correlates with an
altered expression of cell wall modifying enzymes and changes in the
pectin network of the phosphate-deprived root tip, supporting the
hypothesis that pectins are involved in iron binding and/or phosphate
mobilization.
Publikation
Gasperini, D.; Greenland, A.; Hedden, P.; Dreos, R.; Harwood, W.; Griffiths, S. Genetic and physiological analysis of Rht8 in
bread wheat: an alternative source of semi-dwarfism with a reduced
sensitivity to brassinosteroids J Exp Bot 63, 4419-4436, (2012) DOI: 10.1093/jxb/ers138
Over the next decade, wheat grain production
must increase to meet the demand of a fast growing human population. One
strategy to meet this challenge is to raise wheat productivity by
optimizing plant stature. The Reduced height 8 (Rht8) semi-dwarfing gene
is one of the few, together with the Green Revolution genes, to reduce
stature of wheat (Triticum aestivum L.), and improve lodging resistance,
without compromising grain yield. Rht8 is widely used in dry
environments such as Mediterranean countries where it increases plant
adaptability. With recent climate change, its use could become
increasingly important even in more northern latitudes. In the present
study, the characterization of Rht8 was furthered. Morphological
analyses show that the semi-dwarf phenotype of Rht8 lines is due to
shorter internodal segments along the wheat culm, achieved through
reduced cell elongation. Physiological experiments show that the reduced
cell elongation is not due to defective gibberellin biosynthesis or
signalling, but possibly to a reduced sensitivity to brassinosteroids.
Using a fine-resolution mapping approach and screening 3104 F2
individuals of a newly developed mapping population, the Rht8 genetic
interval was reduced from 20.5 cM to 1.29 cM. Comparative genomics with
model genomes confined the Rht8 syntenic intervals to 3.3 Mb of the
short arm of rice chromosome 4, and to 2 Mb of Brachypodium distachyon
chromosome 5. The very high resolution potential of the plant material
generated is crucial for the eventual cloning of Rht8.
Publikation
Stenzel, I.; Otto, M.; Delker, C.; Kirmse, N.; Schmidt, D.; Miersch, O.; Hause, B.; Wasternack, C. ALLENE OXIDE CYCLASE (AOC) gene family members of
Arabidopsis thaliana: tissue- and organ-specific promoter activities and
in vivo heteromerization J Exp Bot 63, 6125-6138, (2012) DOI: 10.1093/jxb/ers261
Jasmonates are important signals in plant stress responses and plant development. An essential step in the biosynthesis of jasmonic acid (JA) is catalysed by ALLENE OXIDE CYCLASE (AOC) which establishes the naturally occurring enantiomeric structure of jasmonates. In Arabidopsis thaliana, four genes encode four functional AOC polypeptides (AOC1, AOC2, AOC3, and AOC4) raising the question of functional redundancy or diversification. Analysis of transcript accumulation revealed an organ-specific expression pattern, whereas detailed inspection of transgenic lines expressing the GUS reporter gene under the control of individual AOC promoters showed partially redundant promoter activities during development: (i) In fully developed leaves, promoter activities of AOC1, AOC2, and AOC3 appeared throughout all leaf tissue, but AOC4 promoter activity was vascular bundle-specific; (ii) only AOC3 and AOC4 showed promoter activities in roots; and (iii) partially specific promoter activities were found for AOC1 and AOC4 in flower development. In situ hybridization of flower stalks confirmed the GUS activity data. Characterization of single and double AOC loss-of-function mutants further corroborates the hypothesis of functional redundancies among individual AOCs due to a lack of phenotypes indicative of JA deficiency (e.g. male sterility). To elucidate whether redundant AOC expression might contribute to regulation on AOC activity level, protein interaction studies using bimolecular fluorescence complementation (BiFC) were performed and showed that all AOCs can interact among each other. The data suggest a putative regulatory mechanism of temporal and spatial fine-tuning in JA formation by differential expression and via possible heteromerization of the four AOCs.
Publikation
Schilling, S.; Stenzel, I.; von Bohlen, A.; Wermann, M.; Schulz, K.; Demuth, H.-U.; Wasternack, C. Isolation and characterization of the glutaminyl
cyclases from Solanum tuberosum and Arabidopsis thaliana: implications
for physiological functions Biol. Chem 388, 145-153, (2007) DOI: 10.1515/BC.2007.016
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