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Publikation

Serra, P.; Carbonell, A.; Navarro, B.; Gago-Zachert, S.; Li, S.; Di Serio, F.; Flores, R.; Symptomatic plant viroid infections in phytopathogenic fungi: A request for a critical reassessment Proc. Natl. Acad. Sci. U.S.A. 117, 10126-10128, (2020) DOI: 10.1073/pnas.1922249117

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Publikation

Berens, M. L.; Wolinska, K. W.; Spaepen, S.; Ziegler, J.; Nobori, T.; Nair, A.; Krüler, V.; Winkelmüller, T. M.; Wang, Y.; Mine, A.; Becker, D.; Garrido-Oter, R.; Schulze-Lefert, P.; Tsuda, K.; Balancing trade-offs between biotic and abiotic stress responses through leaf age-dependent variation in stress hormone cross-talk Proc. Natl. Acad. Sci. U.S.A. 116, 2364-2373, (2019) DOI: 10.1073/pnas.1817233116

In nature, plants must respond to multiple stresses simultaneously, which likely demands cross-talk between stress-response pathways to minimize fitness costs. Here we provide genetic evidence that biotic and abiotic stress responses are differentially prioritized in Arabidopsis thaliana leaves of different ages to maintain growth and reproduction under combined biotic and abiotic stresses. Abiotic stresses, such as high salinity and drought, blunted immune responses in older rosette leaves through the phytohormone abscisic acid signaling, whereas this antagonistic effect was blocked in younger rosette leaves by PBS3, a signaling component of the defense phytohormone salicylic acid. Plants lacking PBS3 exhibited enhanced abiotic stress tolerance at the cost of decreased fitness under combined biotic and abiotic stresses. Together with this role, PBS3 is also indispensable for the establishment of salt stress- and leaf age-dependent phyllosphere bacterial communities. Collectively, our work reveals a mechanism that balances trade-offs upon conflicting stresses at the organism level and identifies a genetic intersection among plant immunity, leaf microbiota, and abiotic stress tolerance.
Publikation

Dinesh, D. C.; Kovermann, M.; Gopalswamy, M.; Hellmuth, A.; Calderón Villalobos, L. I. A.; Lilie, H.; Balbach, J.; Abel, S.; Solution structure of the PsIAA4 oligomerization domain reveals interaction modes for transcription factors in early auxin response Proc. Natl. Acad. Sci. U.S.A. 112, 6230-6235, (2015) DOI: 10.1073/pnas.1424077112

The plant hormone auxin activates primary response genes by facilitating proteolytic removal of AUXIN/INDOLE-3-ACETIC ACID (AUX/IAA)-inducible repressors, which directly bind to transcriptional AUXIN RESPONSE FACTORS (ARF). Most AUX/IAA and ARF proteins share highly conserved C-termini mediating homotypic and heterotypic interactions within and between both protein families. The high-resolution NMR structure of C-terminal domains III and IV of the AUX/IAA protein PsIAA4 from pea (Pisum sativum) revealed a globular ubiquitin-like β-grasp fold with homologies to the Phox and Bem1p (PB1) domain. The PB1 domain of wild-type PsIAA4 features two distinct surface patches of oppositely charged amino acid residues, mediating front-to-back multimerization via electrostatic interactions. Mutations of conserved basic or acidic residues on either face suppressed PsIAA4 PB1 homo-oligomerization in vitro and confirmed directional interaction of full-length PsIAA4 in vivo (yeast two-hybrid system). Mixing of oppositely mutated PsIAA4 PB1 monomers enabled NMR mapping of the negatively charged interface of the reconstituted PsIAA4 PB1 homodimer variant, whose stoichiometry (1:1) and equilibrium binding constant (KD ∼6.4 μM) were determined by isothermal titration calorimetry. In silico protein–protein docking studies based on NMR and yeast interaction data derived a model of the PsIAA4 PB1 homodimer, which is comparable with other PB1 domain dimers, but indicated considerable differences between the homodimeric interfaces of AUX/IAA and ARF PB1 domains. Our study provides an impetus for elucidating the molecular determinants that confer specificity to complex protein–protein interaction circuits between members of the two central families of transcription factors important to the regulation of auxin-responsive gene expression.
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