Full Abstract Book - Wisconsin Union - University of Wisconsin ...

ICAR 2011
University of Wisconsin–Madison
HcPro requires EDF2 for induction of the endogenous suppressors of RNA silencing, FIERY1 and CML38. The RAV/EDFs are therefore
potential novel integrators of hormone signaling and RNA silencing. To further understand the functions of these TFs, we investigated their
importance in the response to ethylene (ET). We found that expression of EDFs 1-4 is ET-inducible and that EIN3, the key transcriptional
activator of ET signaling, binds the EDF1 promoter. This EIN3 binding site was sufficient to direct ET-responsive expression of a GUS
transgene in planta. Furthermore, knockout mutations indicate that all four EDFs are required for normal ET sensitivity, and overexpression
of a truncated EDF1 caused constitutive activation and repression of different branches of the ET response pathway. Knowledge of the
in planta binding targets of the RAV/EDF TFs would provide great insight into their mode(s) of action, but these are currently unknown.
We are employing chromatin immunopreciptiation coupled with deep sequencing to identify these targets. A recombineering approach
is being used to generate A. thaliana lines expressing RAV/EDFs tagged with a Ypet epitope. The advantages of this approach are that it
will maintain genomic contexts and native gene expression patterns. We will investigate how the binding patterns of RAV/EDFs change
in response to hormone stimuli using these tools, and will characterize the associated transcriptional responses by RNAseq. This will
result in much greater understanding of the roles of RAV/EDFs in specific signaling pathways and as integrators of multiple pathways.
242 Growth regulation in response to cross-kingdom communication
Louisa Liberman, Philip Benfey
Duke University, Durham, NC, USA
Organisms sense and adapt to their environment to efficiently use resources and avoid predators and toxins. As sessile organisms
plants depend on rapid adaptation to external cues for survival. Plant roots provide stability while facilitating nutrient and water uptake
from soil teeming with microbes, fungi and invertebrates, all competing for resources. Cooperative relationships exist between plants and
microbes, but molecular mechanisms underlying mutualism remain unclear. Complementary approaches have been used to determine
the effect of beneficial microbes on root architecture and transcriptional regulation in Arabidopsis thaliana. Phenotypic changes in root
growth and architecture upon exposure to multiple beneficial microbes were observed. Candidate mutant lines as well as Arabidopsis
ecotypes were screened to determine their role in sensing and responding to bacterial signals. Transcriptional profiling will be used to
identify genes that are differentially regulated in response to growth-promoting bacteria. The ultimate goal is to elucidate the molecular
mechanisms underlying root-microbe interactions that result in increased growth.
243 Receptor-like Cytoplasmic Kinases in Plant Innate Immunity
Zuh-Jyh Lin, Jun Liu, Gitta Coaker
University of California, Davis, CA
Arabidopsis thaliana receptor-like cytoplasmic kinases (RLCKs), are a subset of the receptor like kinases (RLKs) but lack both
extracellular and transmembrane domains. Several members of the Arabidopsis RLCK subfamily VII have been conclusively linked
to plant innate immunity. Members PBS1 and RIPK are crucial components in RPS5 and RPM1 mediated effector triggered immunity,
respectively, while BIK1 has been shown to participate in the signaling cascade triggered by flagellin perception. Furthermore, numerous
RLCK-VII's have been shown to be cleaved by the Pseudomonas syringae effector AvrPphB and can be correlated with the dampening
of PAMP triggered immunity in plants expressing AvrPphB. The RLCK subfamily VII is rather large, consisting of 46 members, and
given the existing lines of evidence it is probable that additional RLCK-VII's may be involved in plant immunity. To identify these,
public Arabidopsis microarray experiments were examined for RLCK-VII's exhibiting differential regulation in response to biotic
stress. TDNA insertion lines for these particular RLCK-VII's were then obtained and subjected to disease phenotyping; two were found
to exhibit enhanced disease resistance and additional efforts will be undertaken to elucidate their role in plant innate immunity. These
efforts will entail an examination of well-established plant immune responses in the mutants for aberrant phenotypes and a search for
protein interactors via yeast two hybrid and immunoprecipitation experiments.
244 Molecular Characterization of mlo-based Powdery Mildew Resistance and the Role of Heterotrimeric
G-Protein Signaling in Arabidopsis Defense
Justine Lorek 1 , Pawel Bednarek 3 , Alan Jones 2 , Ralph Panstruga 1
1
Max Planck Institute for Plant Breeding Research, Cologne, Germany, 2 University of North Carolina, North
Carolina, USA, 3 Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
Powdery mildew is a common fungal disease of monocotyledonous and dicotyledonous plant species. Successful pathogenesis
by the biotrophic fungus depends on the presence of plant-specific MLO (MILDEW RESISTANCE LOCUS O) proteins, as mutations
in particular MLO genes confer durable powdery mildew resistance in barley, tomato and Arabidopsis. In the absence of MLO, fungal
spores fail to invade the host epidermal cell, resulting in an early termination of fungal pathogenesis.
MLO proteins define a family of heptahelical plasma membrane-localized proteins, reminiscent of G-protein coupled receptors
(GPCRs) in metazoans that activate heterotrimeric G-protein signaling. A genetic approach was chosen in this study to assess the role of
MLO proteins as putative plant GPCRs and results from these experiments demonstrate that powdery mildew susceptibility conferred by
MLO is independent of the heterotrimeric G-protein complex. However, data from this analysis suggest a function of the heterotrimeric
G-protein in basal defense mechanisms against powdery mildew fungi as well as in the integration of MAMP (microbe-associated
molecular patterns) perception into downstream immune responses.
Metabolomic analysis performed in this study indicate that the adapted powdery mildew fungus, Golovinomyces orontii, is able to
suppress the accumulation of the defense-relevant indolic glucosinolate, 4MI3G (4-methoxyindol-3-ylmethylglucosinolate) in Arabidopsis,
thereby inhibiting the PEN2-dependent glucosinolate defense pathway. This inhibition requires functional MLO, suggesting that successful
Poster: Biotic Interactions/Biotic Stress