100 research outputs found
Small RNAs and extracellular vesicles: New mechanisms of cross-species communication and innovative tools for disease control
Highlights of the mini-symposium on extracellular vesicles in inter-organismal communication, held in Munich, Germany, August 2018
All living organisms secrete molecules for intercellular communication. Recent research has revealed that extracellular vesicles (EVs) play an important role in inter-organismal cell-to-cell communication by transporting diverse messenger molecules, including RNA, DNA, lipids and proteins. These discoveries have raised fundamental questions regarding EV biology. How are EVs biosynthesized and loaded with messenger/cargo molecules? How are EVs secreted into the extracellular matrix? What are the EV uptake mechanisms of recipient cells? As EVs are produced by all kind of organisms, from unicellular bacteria and protists, filamentous fungi and oomycetes, to complex multicellular life forms such as plants and animals, basic research in diverse model systems is urgently needed to shed light on the multifaceted biology of EVs and their role in inter-organismal communications. To help catalyse progress in this emerging field, a mini-symposium was held in Munich, Germany in August 2018. This report highlights recent progress and major questions being pursued across a very diverse group of model systems, all united by the question of how EVs contribute to inter-organismal communication
Microguards and micromessengers of the genome
The regulation of gene expression is of fundamental importance to maintain organismal function and integrity and requires a multifaceted and highly ordered sequence of events. The cyclic nature of gene expression is known as ‘transcription dynamics’. Disruption or perturbation of these dynamics can result in significant fitness costs arising from genome instability, accelerated ageing and disease. We review recent research that supports the idea that an important new role for small RNAs, particularly microRNAs (miRNAs), is in protecting the genome against short-term transcriptional fluctuations, in a process we term ‘microguarding’. An additional emerging role for miRNAs is as ‘micromessengers’—through alteration of gene expression in target cells to which they are trafficked within microvesicles. We describe the scant but emerging evidence that miRNAs can be moved between different cells, individuals and even species, to exert biologically significant responses. With these two new roles, miRNAs have the potential to protect against deleterious gene expression variation from perturbation and to themselves perturb the expression of genes in target cells. These interactions between cells will frequently be subject to conflicts of interest when they occur between unrelated cells that lack a coincidence of fitness interests. Hence, there is the potential for miRNAs to represent both a means to resolve conflicts of interest, as well as instigate them. We conclude by exploring this conflict hypothesis, by describing some of the initial evidence consistent with it and proposing new ideas for future research into this exciting topic
The Extended Nambu-Jona-Lasinio Model and Hidden Local Symmetry of Low Energy QCD
Using the standard auxiliary field method, we derive from the extended
Nambu-Jona-Lasinio model an effective meson action containing vector and
axial-vector mesons in addition to Goldstone bosons. The vector and
axial-vector mesons in this effective action transform as gauge fields of
hidden local symmetry . Here, the
realization of enlarged hidden local symmetry is accomplished via the
introduction of two kinds of ``compensating'' fields. For obtaining the
intrinsic-parity violating part of the action, we generalize the standard
gauged Wess-Zumino-Witten action such that it also contains two kinds of
``compensators'' in addition to the usual Goldstone bosons as well as the
vector and axial-vector mesons. This generalized gauged Wess-Zumino-Witten
action turns out to have symmetry, where
being the usual global chiral symmetry
while being the hidden local symmetry. This
means that has no gauge anomaly and its associated vector and
axial-vector mesons can be regarded as gauge bosons of . The
introduction of the coupling with the external electroweak fields requires us
to gauge some appropriate subgroup of . To perform it in consistent
with the anomaly structure of QCD is a nontrivial problem. We explain how this
can be done, following the recent suggestion by several authors.Comment: 49pages, LaTex, 2 Postscript figure
Regulation of proteinaceous effector expression in phytopathogenic fungi
Effectors are molecules used by microbial pathogens to facilitate infection via effector-triggered susceptibility or tissue necrosis in their host. Much research has been focussed on the identification and elucidating the function of fungal effectors during plant pathogenesis. By comparison, knowledge of how phytopathogenic fungi regulate the expression of effector genes has been lagging. Several recent studies have illustrated the role of various transcription factors, chromosome-based control, effector epistasis, and mobilisation of endosomes within the fungal hyphae in regulating effector expression and virulence on the host plant. Improved knowledge of effector regulation is likely to assist in improving novel crop protection strategies
Several wall-associated kinases participate positively and negatively in basal defense against rice blast fungus
Evolution of the EKA family of powdery mildew avirulence-effector genes from the ORF 1 of a LINE retrotransposon
Antiviral Silencing and Suppression of Gene Silencing in Plants
RNA silencing is an evolutionary conserved sequence-specific gene inactivation mechanism that contributes to the control of development, maintains heterochromatin, acts in stress responses, DNA repair and defends against invading nucleic acids like transposons and viruses. In plants RNA silencing functions as one of the main immune systems. RNA silencing process involves the small RNAs and trans factor components like Dicers, Argonautes and RNA-dependent RNA poly- merases. To deal with host antiviral silencing responses viruses evolved mecha- nisms to avoid or counteract this, most notably through expression of viral suppressors of RNA silencing. Due to the overlap between endogenous and antiviral silencing pathways while blocking antiviral pathways viruses also impact endogenous silencing processes. Here we provide an overview of antiviral silencing pathway, host factors implicated in it and the crosstalk between antiviral and endogenous branches of silencing. We summarize the current status of knowledge about the viral counter-defense strategies acting at various steps during virus infection in plants with the focus on representative, well studied silencing suppres- sor proteins. Finally we discuss future challenges of the antiviral silencing and counter-defense research field
A nested hydrodynamic model of the Cariaco Basin (Venezuela): study of the basin interactions with the Caribbean Sea
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