Publications
Guerra, T.; Schilling, S.; Hake, K.; Gorzolka, K.; Sylvester, F.-P.; Conrads, B.; Westermann, B.; Romeis, T. Calcium‐dependent protein kinase 5 links
calcium‐signaling with N‐Hydroxy‐L‐pipecolic acid‐ and SARD1‐dependent
immune memory in systemic acquired resistance New Phytol 225, 310-325, (2020) DOI: 10.1111/nph.16147
Systemic acquired resistance (SAR) prepares
infected plants for faster and stronger defense activation upon
subsequent attacks. SAR requires an information relay from primary
infection to distal tissue and the initiation and maintenance of a
self‐maintaining phytohormone salicylic acid (SA)‐defense loop.In
spatial and temporal resolution, we show that calcium‐dependent protein
kinase CPK5 contributes to immunity and SAR. In local basal resistance,
CPK5 functions upstream of SA synthesis, perception, and signaling. In
systemic tissue, CPK5 signaling leads to accumulation of SAR‐inducing
metabolite N‐hydroxy‐L‐pipecolic acid (NHP) and SAR marker genes,
including Systemic Acquired Resistance Deficient 1 (SARD1)Plants of
increased CPK5, but not CPK6, signaling display an ‘enhanced SAR’
phenotype towards a secondary bacterial infection. In the sard1‐1
background, CPK5‐mediated basal resistance is still mounted, but NHP
concentration is reduced and enhanced SAR is lost.The biochemical
analysis estimated CPK5 half maximal kinase activity for calcium, K50
[Ca2+], to be c. 100 nM, close to the cytoplasmic resting level. This
low threshold uniquely qualifies CPK5 to decode subtle changes in
calcium, a prerequisite to signal relay and onset and maintenance of
priming at later time points in distal tissue. Our data explain why CPK5
functions as a hub in basal and systemic plant immunity.
Publications
Durian, G.; Sedaghatmehr, M.; Matallana-Ramirez, L. P.; Schilling, S. M.; Schaepe, S.; Guerra, T.; Herde, M.; Witte, C.-P.; Mueller-Roeber, B.; Schulze, W. X.; Balazadeh, S.; Romeis, T. Calcium-Dependent Protein Kinase CPK1 Controls Cell Death by In Vivo Phosphorylation of Senescence Master Regulator ORE1 Plant Cell 32, 1610-1625, (2020) DOI: 10.1105/tpc.19.00810
Calcium-regulated protein kinases are key
components of are key components of intracellular signaling in plants
that mediate rapid stress-induced responses to changes in the
environment. To identify in vivo phosphorylation substrates of
CALCIUM-DEPENDENT PROTEIN KINASE1 (CPK1), we analyzed the conditional
expression of constitutively active CPK1 in conjunction with in vivo
phosphoproteomics. We identified Arabidopsis thaliana ORESARA1 (ORE1),
the developmental master regulator of senescence, as a direct CPK1
phosphorylation substrate. CPK1 phosphorylates ORE1 at a hotspot within
an intrinsically disordered region. This augments transcriptional
activation by ORE1 of its downstream target gene BIFUNCTIONAL NUCLEASE1
(BFN1). Plants that overexpress ORE1, but not an ORE1 variant lacking
the CPK1 phosphorylation hotspot, promote early senescence. Furthermore,
ORE1 is required for enhanced cell death induced by CPK1 signaling. Our
data validate the use of conditional expression of an active enzyme
combined with phosphoproteomics to decipher specific kinase target
proteins of low abundance, of transient phosphorylation, or in yet
undescribed biological contexts. Here, we have identified that
senescence is not just under molecular surveillance manifested by
stringent gene regulatory control over ORE1. In addition, the decision
to die is superimposed by an additional layer of control towards ORE1
via its post-translational modification linked to the calcium-regulatory
network through CPK1.
Publications
Tabassum, N.; Eschen‐Lippold, L.; Athmer, B.; Baruah, M.; Brode, M.; Maldonado‐Bonilla, L. D.; Hoehenwarter, W.; Hause, G.; Scheel, D.; Lee, J. Phosphorylation‐dependent control of an RNA
granule‐localized protein that fine‐tunes defence gene expression at a
post‐transcriptional level Plant J 101, 1023-1039, (2020) DOI: 10.1111/tpj.14573
Mitogen‐activated protein kinase (MAPK)
cascades are key signalling modules of plant defence responses to
pathogen‐associated molecular patterns (PAMPs, e.g. bacterial flg22
peptide). The Tandem Zinc Finger Protein 9 (TZF9) is an RNA‐binding
protein that is phosphorylated by two PAMP‐responsive MAPKs, MPK3 and
MPK6. We mapped the major phosphosites in TZF9 and showed their
importance for controlling in vitro RNA‐binding activity, in vivo
flg22‐induced rapid disappearance of TZF9‐labelled processing body‐like
structures and TZF9 protein turnover. Microarray analysis showed a
strong discordance between transcriptome (total mRNA) and translatome
(polysome‐associated mRNA) in the tzf9 mutant, with more mRNAs
associated to ribosomes in the absence of TZF9. This suggests that TZF9
may sequester and inhibit translation of subsets of mRNAs. Fittingly,
TZF9 physically interacts with poly(A)‐binding protein 2 (PAB2), a
hallmark constituent of stress granules – a site for stress‐induced
translational stalling/arrest. TZF9 even promotes stress granule
assembly in the absence of stress. Hence, MAPKs may control defence gene
expression post‐transcriptionally through release from translation
arrest within TZF9‐PAB2‐containing RNA granules or perturbing PAB2
functions in translation control (e.g. in the mRNA closed‐loop model of
translation).
Publications
Wang, W.; Liu, N.; Gao, C.; Cai, H.; Romeis, T.; Tang, D. The Arabidopsis exocyst subunits EXO70B1 and EXO70B2 regulate FLS2 homeostasis at the plasma membrane New Phytol 227, 529-544, (2020) DOI: 10.1111/nph.16515
The plasma membrane (PM)‐localized receptor kinase
FLAGELLIN SENSING 2 (FLS2) recognizes bacterial flagellin or its
immunogenic epitope flg22, and initiates microbe‐associated molecular
pattern‐triggered immunity, which inhibits infection by bacterial
pathogens. The localization, abundance and activity of FLS2 are under
dynamic control.Here, we demonstrate that Arabidopsis thaliana EXO70B1,
a subunit of the exocyst complex, plays a critical role in FLS2
signaling that is independent of the truncated Toll/interleukin‐1
receptor‐nucleotide binding sequence protein TIR‐NBS2 (TN2). In the
exo70B1‐3 mutant, the abundance of FLS2 protein at the PM is
diminished, consistent with the impaired flg22 response of this mutant.
EXO70B1‐GFP plants showed increased FLS2 accumulation at the PM and
therefore enhanced FLS2 signaling.The EXO70B1‐mediated trafficking of
FLS2 to the PM is partially independent of the PENETRATION 1
(PEN1)‐containing secretory pathway. In addition, EXO70B1 interacts with
EXO70B2, a close homolog of EXO70B1, and both proteins associate with
FLS2 and contribute to the accumulation of FLS2 at the PM.Taken
together, our data suggest that the exocyst complex subunits EXO70B1 and
EXO70B2 regulate the trafficking of FLS2 to the PM, which represents a
new layer of regulation of FLS2 function in plant immunity.
Publications
Dietz, S.; Herz, K.; Gorzolka, K.; Jandt, U.; Bruelheide, H.; Scheel, D. Root exudate composition of grass and forb species in natural grasslands Sci Rep 10, 10691, (2020) DOI: 10.1038/s41598-019-54309-5
Plants exude a diverse cocktail of metabolites
into the soil as response to exogenous and endogenous factors. So far,
root exudates have mainly been studied under artificial conditions due
to methodological difficulties. In this study, each five perennial grass
and forb species were investigated for polar and semi-polar metabolites
in exudates under field conditions. Metabolite collection and
untargeted profiling approaches combined with a novel classification
method allowed the designation of 182 metabolites. The composition of
exuded polar metabolites depended mainly on the local environment,
especially soil conditions, whereas the pattern of semi-polar
metabolites was primarily affected by the species identity. The profiles
of both polar and semi-polar metabolites differed between growth forms,
with grass species being generally more similar to each other and more
responsive to the abiotic environment than forb species. This study
demonstrated the feasibility of investigating exudates under field
conditions and to identify the driving factors of exudate composition.
Printed publications
Schulz, P.; Piepenburg, K.; Lintermann, R.; Herde, M.; Schöttler, M. A.; Schmidt, L. K.; Ruf, S.; Kudla, J.; Romeis, T.; Bock, R. Improving plant drought tolerance and growth under water limitation through combinatorial engineering of signaling networks Plant Biotechnol J (2020) DOI: 10.1111/pbi.13441
Agriculture is by far the biggest water
consumer on our planet, accounting for 70 percent of all freshwater
withdrawals. Climate change and a growing world population increase
pressure on agriculture to use water more efficiently (‘more crop per
drop’). Water‐use efficiency (WUE) and drought tolerance of crops are
complex traits that are determined by many physiological processes whose
interplay is not well understood. Here we describe a combinatorial
engineering approach to optimize signaling networks involved in the
control of stress tolerance. Screening a large population of
combinatorially transformed plant lines, we identified a combination of
calcium‐dependent protein kinase genes that confers enhanced drought
stress tolerance and improved growth under water‐limiting conditions.
Targeted introduction of this gene combination into plants increased
plant survival under drought and enhanced growth under water‐limited
conditions. Our work provides an efficient strategy for engineering
complex signaling networks to improve plant performance under adverse
environmental conditions, which does not depend on prior understanding
of network function.
Preprints
Vainonen, J. P.; Shapiguzov, A.; Krasensky-Wrzaczek, J.; De Masi, R.; Gossens, R.; Danciu, I.; Battchikova, N.; Jonak, C.; Wirthmueller, L.; Wrzaczek, M.; Kangasjärvi, J. Arabidopsis Poly(ADP-ribose)-binding protein RCD1 interacts with Photoregulatory Protein Kinases in nuclear bodies bioRxiv (2020) DOI: 10.1101/2020.07.02.184937
Continuous reprograming of gene expression in
response to environmental signals in plants is achieved through
signaling hub proteins that integrate external stimuli and
transcriptional responses. RADICAL-INDUCED CELL DEATH1 (RCD1) functions
as a nuclear hub protein, which interacts with a variety of
transcription factors with its C-terminal RST domain and thereby acts as
a co-regulator of numerous plant stress reactions. Here a previously
function for RCD1 as a novel plant PAR reader protein is shown; RCD1
functions as a scaffold protein, which recruits transcription factors to
specific locations inside the nucleus in PAR-dependent manner. The
N-terminal WWE- and PARP-like domains of RCD1 bind poly(ADP-ribose)
(PAR) and determine its localization to nuclear bodies (NBs), which is
prevented by chemical inhibition of PAR synthesis. RCD1 also binds and
recruits Photoregulatory Protein Kinases (PPKs) to NBs. The PPKs, which
have been associated with circadian clock, abscisic acid, and light
signaling pathways, phosphorylate RCD1 at multiple sites in the
intrinsically disordered region between the WWE- and PARP-like-domains,
which affects the stability and function of RCD1 in the nucleus.
Phosphorylation of RCD1 by PPKs provides a mechanism where turnover of a
PAR-binding transcriptional co-regulator is controlled by nuclear
phosphorylation signaling pathways.
Printed publications
Trempel, F.; Eschen‐Lippold, L.; Bauer, N.; Ranf, S.; Westphal, L.; Scheel, D.; Lee, J. A mutation in Asparagine‐Linked Glycosylation 12
(ALG12) leads to receptor misglycosylation and attenuated responses to
multiple microbial elicitors FEBS Lett (2020) DOI: 10.1002/1873-3468.13850
Changes in cellular calcium levels are one of
the earliest signalling events in plants exposed to pathogens or other
exogenous factors. In a genetic screen, we identified an Arabidopsis
thaliana ‘changed calcium elevation 1 ’ (cce1 ) mutant with attenuated
calcium response to the bacterial flagellin flg22 peptide and several
other elicitors. Whole genome re‐sequencing revealed a mutation in ALG12
(Asparagine‐Linked Glycosylation 12 ) that encodes the
mannosyltransferase responsible for adding the eighth mannose residue in
an α‐1,6 linkage to the dolichol‐PP‐oligosaccharide N ‐glycosylation
glycan tree precursors. While properly targeted to the plasma membrane,
misglycosylation of several receptors in the cce1 background suggests
that N ‐glycosylation is required for proper functioning of client
proteins.
Printed publications
Alternative splicing provides a fundamental and
ubiquitous mechanism of gene regulation. Stimuli-induced retention of
introns introduces novel proteoforms with altered signalling output:
full-length CPK28 blocks immune signalling, while a truncated variant,
lacking calcium responsiveness, promotes it.
Publications
Dietz, S.; Herz, K.; Döll, S.; Haider, S.; Jandt, U.; Bruelheide, H.; Scheel, D. Semi‐polar root exudates in natural grassland communities Ecol Evol 9, 5526-5541, (2019) DOI: 10.1002/ece3.5043
In the rhizosphere, plants are exposed to a
multitude of different biotic and abiotic factors, to which they respond
by exuding a wide range of secondary root metabolites. So far, it has
been unknown to which degree root exudate composition is
species‐specific and is affected by land use, the local impact and local
neighborhood under field conditions. In this study, root exudates of 10
common grassland species were analyzed, each five of forbs and grasses,
in the German Biodiversity Exploratories using a combined phytometer
and untargeted liquid chromatography‐mass spectrometry (LC‐MS) approach.
Redundancy analysis and hierarchical clustering revealed a large set of
semi‐polar metabolites common to all species in addition to
species‐specific metabolites. Chemical richness and exudate composition
revealed that forbs, such as Plantago lanceolata and Galium species,
exuded more species‐specific metabolites than grasses. Grasses instead
were primarily affected by environmental conditions. In both forbs and
grasses, plant functional traits had only a minor impact on plant root
exudation patterns. Overall, our results demonstrate the feasibility of
obtaining and untargeted profiling of semi‐polar metabolites under field
condition and allow a deeper view in the exudation of plants in a
natural grassland community.