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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

Naumann, C.; Müller, J.; Sakhonwasee, S.; Wieghaus, A.; Hause, G.; Heisters, M.; Bürstenbinder, K.; Abel, S.; The Local Phosphate Deficiency Response Activates Endoplasmic Reticulum Stress-Dependent Autophagy Plant Physiol. 179, 460-476, (2019) DOI: 10.1104/pp.18.01379

Inorganic phosphate (Pi) is often a limiting plant nutrient. In members of the Brassicaceae family, such as Arabidopsis (Arabidopsis thaliana), Pi deprivation reshapes root system architecture to favor topsoil foraging. It does so by inhibiting primary root extension and stimulating lateral root formation. Root growth inhibition from phosphate (Pi) deficiency is triggered by iron-stimulated, apoplastic reactive oxygen species generation and cell wall modifications, which impair cell-to-cell communication and meristem maintenance. These processes require LOW PHOSPHATE RESPONSE1 (LPR1), a cell wall-targeted ferroxidase, and PHOSPHATE DEFICIENCY RESPONSE2 (PDR2), the single endoplasmic reticulum (ER)-resident P5-type ATPase (AtP5A), which is thought to control LPR1 secretion or activity. Autophagy is a conserved process involving the vacuolar degradation of cellular components. While the function of autophagy is well established under nutrient starvation (C, N, or S), it remains to be explored under Pi deprivation. Because AtP5A/PDR2 likely functions in the ER stress response, we analyzed the effect of Pi limitation on autophagy. Our comparative study of mutants defective in the local Pi deficiency response, ER stress response, and autophagy demonstrated that ER stress-dependent autophagy is rapidly activated as part of the developmental root response to Pi limitation and requires the genetic PDR2-LPR1 module. We conclude that Pi-dependent activation of autophagy in the root apex is a consequence of local Pi sensing and the associated ER stress response, rather than a means for systemic recycling of the macronutrient.
Publikation

Hussain, H.; Ziegler, J.; Hause, G.; Wohlrab, J.; Neubert, R. H.; Quantitative Analysis of Free Amino Acids and Urea Derived from Isolated Corneocytes of Healthy Young, Healthy Aged, and Diseased Skin Skin Pharmacol. Physiol. 32, 94-100, (2019) DOI: 10.1159/000495992

Background/Aims: Free amino acids (FAAs) and urea, present inside the corneocytes, can be important indicators of skin condition. However, due to the lack of a standard extraction protocol for FAAs from corneocytes, conflicting research results have been reported. Therefore, the purpose of this study was (1) to standardize the extraction protocol and (2) to investigate FAA profiles in healthy young and healthy old volunteers, as well as in psoriasis and atopic dermatitis patients. Methods: Skin samples were collected from four groups (healthy young, healthy old, and psoriasis and atopic dermatitis patients) with 5 volunteers per group. Corneocytes were isolated and examined microscopically. FAAs and urea were extracted from the isolated corneocytes, and their amounts were quantified using LC-ESI/MS/MS (after derivatization with Fmoc-Cl) and colorimetric methods, respectively. Results: The micrographs of the corneocytes showed no morphological features attributable to age or disease conditions. The highest and lowest concentrations of total FAAs and urea were observed in the healthy old group and the healthy young group, respectively. Unlike the other FAAs and urea, citrulline was found at a higher level in the healthy young group than in the disease groups. Conclusion: This study suggests that the levels of FAAs and urea in the skin are affected by age and skin conditions (healthy/diseased). However, further studies are needed to show the effects of different skin conditions on the levels of FAAs and urea.
Publikation

García, M. L.; Bó, E. D.; da Graça, J. V.; Gago-Zachert, S.; Hammond, J.; Moreno, P.; Natsuaki, T.; Pallás, V.; Navarro, J. A.; Reyes, C. A.; Luna, G. R.; Sasaya, T.; Tzanetakis, I. E.; Vaira, A. M.; Verbeek, M.; ICTV Report Consortium, .; Corrigendum: ICTV Virus Taxonomy Profile: Ophioviridae J. Gen. Virol. 99, 949-949, (2018) DOI: 10.1099/jgv.0.001093

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Publikation

Ibañez, C.; Delker, C.; Martinez, C.; Bürstenbinder, K.; Janitza, P.; Lippmann, R.; Ludwig, W.; Sun, H.; James, G. V.; Klecker, M.; Grossjohann, A.; Schneeberger, K.; Prat, S.; Quint, M.; Brassinosteroids Dominate Hormonal Regulation of Plant Thermomorphogenesis via BZR1 Curr. Biol. 28, 303-310.e3, (2018) DOI: 10.1016/j.cub.2017.11.077

Thermomorphogenesis is defined as the suite of morphological changes that together are likely to contribute to adaptive growth acclimation to usually elevated ambient temperature [1, 2]. While many details of warmth-induced signal transduction are still elusive, parallels to light signaling recently became obvious (reviewed in [3]). It involves photoreceptors that can also sense changes in ambient temperature [3, 4, 5] and act, for example, by repressing protein activity of the central integrator of temperature information PHYTOCHROME-INTERACTING FACTOR 4 (PIF4 [6]). In addition, PIF4 transcript accumulation is tightly controlled by the evening complex member EARLY FLOWERING 3 [7, 8]. According to the current understanding, PIF4 activates growth-promoting genes directly but also via inducing auxin biosynthesis and signaling, resulting in cell elongation. Based on a mutagenesis screen in the model plant Arabidopsis thaliana for mutants with defects in temperature-induced hypocotyl elongation, we show here that both PIF4 and auxin function depend on brassinosteroids. Genetic and pharmacological analyses place brassinosteroids downstream of PIF4 and auxin. We found that brassinosteroids act via the transcription factor BRASSINAZOLE RESISTANT 1 (BZR1), which accumulates in the nucleus at high temperature, where it induces expression of growth-promoting genes. Furthermore, we show that at elevated temperature BZR1 binds to the promoter of PIF4, inducing its expression. These findings suggest that BZR1 functions in an amplifying feedforward loop involved in PIF4 activation. Although numerous negative regulators of PIF4 have been described, we identify BZR1 here as a true temperature-dependent positive regulator of PIF4, acting as a major growth coordinator.
Publikation

García, M. L.; Bó, E. D.; da Graça, J. V.; Gago-Zachert, S.; Hammond, J.; Moreno, P.; Natsuaki, T.; Pallás, V.; Navarro, J. A.; Reyes, C. A.; Luna, G. R.; Sasaya, T.; Tzanetakis, I. E.; Vaira, A. M.; Verbeek, M.; ICTV Report Consortium, .; ICTV Virus Taxonomy Profile: Ophioviridae J. Gen. Virol. 98, 1161-1162, (2017) DOI: 10.1099/jgv.0.000836

The Ophioviridae is a family of filamentous plant viruses, with single-stranded negative, and possibly ambisense, RNA genomes of 11.3–12.5 kb divided into 3–4 segments, each encapsidated separately. Virions are naked filamentous nucleocapsids, forming kinked circles of at least two different contour lengths. The sole genus, Ophiovirus, includes seven species. Four ophioviruses are soil-transmitted and their natural hosts include trees, shrubs, vegetables and bulbous or corm-forming ornamentals, both monocots and dicots. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the Ophioviridae, which is available at http://www.ictv.global/report/ophioviridae.
Publikation

Bürstenbinder, K.; Möller, B.; Plötner, R.; Stamm, G.; Hause, G.; Mitra, D.; Abel, S.; The IQD Family of Calmodulin-Binding Proteins Links Calcium Signaling to Microtubules, Membrane Subdomains, and the Nucleus Plant Physiol. 173, 1692-1708, (2017) DOI: 10.1104/pp.16.01743

Calcium (Ca2+) signaling and dynamic reorganization of the cytoskeleton are essential processes for the coordination and control of plant cell shape and cell growth. Calmodulin (CaM) and closely related calmodulin-like (CML) polypeptides are principal sensors of Ca2+ signals. CaM/CMLs decode and relay information encrypted by the second messenger via differential interactions with a wide spectrum of targets to modulate their diverse biochemical activities. The plant-specific IQ67 DOMAIN (IQD) family emerged as possibly the largest class of CaM-interacting proteins with undefined molecular functions and biological roles. Here, we show that the 33 members of the IQD family in Arabidopsis (Arabidopsis thaliana) differentially localize, using green fluorescent protein (GFP)-tagged proteins, to multiple and distinct subcellular sites, including microtubule (MT) arrays, plasma membrane subdomains, and nuclear compartments. Intriguingly, the various IQD-specific localization patterns coincide with the subcellular patterns of IQD-dependent recruitment of CaM, suggesting that the diverse IQD members sequester Ca2+-CaM signaling modules to specific subcellular sites for precise regulation of Ca2+-dependent processes. Because MT localization is a hallmark of most IQD family members, we quantitatively analyzed GFP-labeled MT arrays in Nicotiana benthamiana cells transiently expressing GFP-IQD fusions and observed IQD-specific MT patterns, which point to a role of IQDs in MT organization and dynamics. Indeed, stable overexpression of select IQD proteins in Arabidopsis altered cellular MT orientation, cell shape, and organ morphology. Because IQDs share biochemical properties with scaffold proteins, we propose that IQD families provide an assortment of platform proteins for integrating CaM-dependent Ca2+ signaling at multiple cellular sites to regulate cell function, shape, and growth.
Publikation

López-Carrasco, A.; Ballesteros, C.; Sentandreu, V.; Delgado, S.; Gago-Zachert, S.; Flores, R.; Sanjuán, R.; Different rates of spontaneous mutation of chloroplastic and nuclear viroids as determined by high-fidelity ultra-deep sequencing PLOS Pathog. 13, e1006547, (2017) DOI: 10.1371/journal.ppat.1006547

Mutation rates vary by orders of magnitude across biological systems, being higher for simpler genomes. The simplest known genomes correspond to viroids, subviral plant replicons constituted by circular non-coding RNAs of few hundred bases. Previous work has revealed an extremely high mutation rate for chrysanthemum chlorotic mottle viroid, a chloroplast-replicating viroid. However, whether this is a general feature of viroids remains unclear. Here, we have used high-fidelity ultra-deep sequencing to determine the mutation rate in a common host (eggplant) of two viroids, each representative of one family: the chloroplastic eggplant latent viroid (ELVd, Avsunviroidae) and the nuclear potato spindle tuber viroid (PSTVd, Pospiviroidae). This revealed higher mutation frequencies in ELVd than in PSTVd, as well as marked differences in the types of mutations produced. Rates of spontaneous mutation, quantified in vivo using the lethal mutation method, ranged from 1/1000 to 1/800 for ELVd and from 1/7000 to 1/3800 for PSTVd depending on sequencing run. These results suggest that extremely high mutability is a common feature of chloroplastic viroids, whereas the mutation rates of PSTVd and potentially other nuclear viroids appear significantly lower and closer to those of some RNA viruses.
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.
Bücher und Buchkapitel

Flores, R.; Gago-Zachert, S.; Serra, P.; De la Peña, M.; Navarro, B.; Chrysanthemum Chlorotic Mottle Viroid (Hadidi, A., et al., eds.). 331-338, (2017) DOI: 10.1016/B978-0-12-801498-1.00031-0

Chrysanthemum chlorotic mottle viroid (CChMVd) (398–401 nt) belongs to genus Pelamoviroid, family Avsunviroidae and, like other members of this family, replicates in plastids through a rolling-circle mechanism involving hammerhead ribozymes. CChMVd RNA adopts a branched conformation stabilized by a kissing-loop interaction, resembling peach latent mosaic viroid in this respect. Chrysanthemum is the only natural and experimental host for CChMVd, which in the most sensitive varieties induces leaf mottling and chlorosis, delay in flowering, and dwarfing. The viroid has been found in major chrysanthemum growing areas including Europe and Asia. There are natural variants in which the change (UUUC→GAAA) mapping at a tetraloop in the CChMVd branched conformation is sufficient to change the symptomatic phenotype into a nonsymptomatic one without altering the viroid titer. Preinfection with nonsymptomatic variants prevents challenge inoculation with symptomatic ones. Moreover, experimental coinoculation with symptomatic and nonsymptomatic CChMVd variants results in symptomless phenotypes only when the latter is in vast excess, thus indicating its lower fitness.
  • Die Leibniz-Gemeinschaft
  • Digitalisierung in der Landwirtschaft
  • Martin-Luther Universität Halle
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