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Publikation

Meena, S. K.; Heidecker, M.; Engelmann, S.; Jaber, A.; de Vries, T.; Triller, S.; Baumann‐Kaschig, K.; Abel, S.; Behrens, S.; Gago-Zachert, S.; Altered expression levels of long noncoding natural antisense transcripts overlapping the UGT73C6 gene affect rosette size in Arabidopsis thaliana Plant J. 113, 460-477, (2023) DOI: 10.1111/tpj.16058

Natural antisense long noncoding RNAs (lncNATs) are involved in the regulation of gene expression in plants, modulating different relevant developmental processes and responses to various stimuli. We have identified and characterized two lncNATs (NAT1UGT73C6 and NAT2UGT73C6, collectively NATsUGT73C6) from Arabidopsis thaliana that are transcribed from gene fully overlapping UGT73C6, a member of the UGT73C subfamily of genes encoding UDP-glycosyltransferases (UGTs). Expression of both NATsUGT73C6 is developmentally controlled and occurs independently of the transcription of UGT73C6 in cis. Downregulation of NATsUGT73C6 levels through artificial microRNAs results in a reduction of the rosette area, while constitutive overexpression of NAT1UGT73C6 or NAT2UGT73C6 leads to the opposite phenotype, an increase in rosette size. This activity of NATsUGT73C6 relies on its RNA sequence, and, although modulation of UGT73C6 in cis cannot be excluded, the observed phenotypes are not a consequence of the regulation of UGT73C6 in trans. The NATsUGT73C6 levels were shown to affect cell proliferation and thus individual leaf size. Consistent with this concept, our data suggest that the NATsUGT73C6 influence the expression levels of key transcription factors involved in regulating leaf growth by modulating cell proliferation. These findings thus reveal an additional regulatory layer on the process of leaf growth.
Publikation

Kuhn, J. H.; Adkins, S.; Alioto, D.; Gago-Zachert, S.; et al., .; 2020 taxonomic update for phylum Negarnaviricota (Riboviria: Orthornavirae), including the large orders Bunyavirales and Mononegavirales Arch. Virol. 165, 3023–3072, (2020) DOI: 10.1007/s00705-020-04731-2

In March 2020, following the annual International Committee on Taxonomy of Viruses (ICTV) ratification vote on newly proposed taxa, the phylum Negarnaviricota was amended and emended. At the genus rank, 20 new genera were added, two were deleted, one was moved, and three were renamed. At the species rank, 160 species were added, four were deleted, ten were moved and renamed, and 30 species were renamed. This article presents the updated taxonomy of Negarnaviricota as now accepted by the ICTV.
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

Anwer, M. U.; Davis, A.; Davis, S. J.; Quint, M.; Photoperiod sensing of the circadian clock is controlled by EARLY FLOWERING 3 and GIGANTEA Plant J. 101, 1397-1410, (2020) DOI: 10.1111/tpj.14604

ELF3 and GI are two important components of the Arabidopsis circadian clock. They are not only essential for the oscillator function but are also pivotal in mediating light inputs to the oscillator. Lack of either results in a defective oscillator causing severely compromised output pathways, such as photoperiodic flowering and hypocotyl elongation. Although single loss of function mutants of ELF3 and GI have been well‐studied, their genetic interaction remains unclear. We generated an elf3 gi double mutant to study their genetic relationship in clock‐controlled growth and phase transition phenotypes. We found that ELF3 and GI repress growth differentially during the night and the day, respectively. Circadian clock assays revealed that ELF3 and GI are essential Zeitnehmers that enable the oscillator to synchronize the endogenous cellular mechanisms to external environmental signals. In their absence, the circadian oscillator fails to synchronize to the light‐dark cycles even under diurnal conditions. Consequently, clock‐mediated photoperiod‐responsive growth and development are completely lost in plants lacking both genes, suggesting that ELF3 and GI together convey photoperiod sensing to the central oscillator. Since ELF3 and GI are conserved across flowering plants and represent important breeding and domestication targets, our data highlight the possibility of developing photoperiod‐insensitive crops by adjusting the allelic combination of these two key genes.
Publikation

Gago-Zachert, S.; Schuck, J.; Weinholdt, C.; Knoblich, M.; Pantaleo, V.; Grosse, I.; Gursinsky, T.; Behrens, S.-E.; Highly efficacious antiviral protection of plants by small interfering RNAs identified in vitro Nucleic Acids Res. 47, 9343-9357, (2019) DOI: 10.1093/nar/gkz678

In response to a viral infection, the plant’s RNA silencing machinery processes viral RNAs into a huge number of small interfering RNAs (siRNAs). However, a very few of these siRNAs actually interfere with viral replication. A reliable approach to identify these immunologically effective siRNAs (esiRNAs) and to define the characteristics underlying their activity has not been available so far. Here, we develop a novel screening approach that enables a rapid functional identification of antiviral esiRNAs. Tests on the efficacy of such identified esiRNAs of a model virus achieved a virtual full protection of plants against a massive subsequent infection in transient applications. We find that the functionality of esiRNAs depends crucially on two properties: the binding affinity to Argonaute proteins and the ability to access the target RNA. The ability to rapidly identify functional esiRNAs could be of great benefit for all RNA silencing-based plant protection measures against viruses and other pathogens.
Preprints

Anwer, M. U.; Davis, A.; Davis, S. J.; Quint, M.; Photoperiod sensing of the circadian clock is controlled by EARLY FLOWERING 3 and GIGANTEA bioRxiv (2018) DOI: 10.1101/321794

ELF3 and GI are two important components of the Arabidopsis circadian clock. They are not only essential for the oscillator function but are also pivotal in mediating light inputs to the oscillator. Lack of either results in a defective oscillator causing severely compromised output pathways, such as photoperiodic flowering and hypocotyl elongation. Although single loss of function mutants of ELF3 and GI have been well-studied, their genetic interaction remains unclear. We generated an elf3 gi double mutant to study their genetic relationship in clock-controlled growth and phase transition phenotypes. We found that ELF3 and GI repress growth differentially during the night and the day, respectively. Circadian clock assays revealed that ELF3 and GI are essential Zeitnehmers that enable the oscillator to synchronize the endogenous cellular mechanisms to external environmental signals. In their absence, the circadian oscillator fails to synchronize to the light-dark cycles even under diurnal conditions. Consequently, clock-mediated photoperiod-responsive growth and development is completely lost in plants lacking both genes, suggesting that ELF3 and GI together convey photoperiod sensing to the central oscillator. Since ELF3 and GI are conserved across flowering plants and represent important breeding and domestication targets, our data highlight the possibility of developing photoperiod-insensitive crops by adjusting the allelic combination of these two key genes.
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

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

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.
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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