Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Volume 509 Issue 7501, 22 May 2014

A conjugating pair of Paramecium cells visualized by confocal microscopy: the mating-type O cell was transformed to express fluorescent-labelled ciliary protein (shown in yellow), and both O and E cells are decorated with the TAP952 anti-monoglycylated tubulin antibody (shown in red). The protozoan Paramecium, widely studied as a typical ciliate, multiplies asexually by binary fission much of the time, but under certain conditions will reproduce sexually. Two mating types, E and O, were discovered in 1937 but only now has the molecular basis for maternal inheritance of mating type been elucidated. Eric Meyer and colleagues show in Paramecium tetraurelia that mating type E depends on expression of the transmembrane protein mtA, and the default type O is determined during development by excision of the mtA promoter by scnRNAs, a class of small ‘scan� RNA that reprograms the Paramecium genome during sexual reproduction by recognizing and excising transposable elements. A similar switch mechanism, involving a different gene, mtB, has evolved independently in a sibling species P. septaurelia, implying that exaptation of the scnRNA pathway may be a general mechanism for transgenerational epigenetic inheritance of differentiated states in Paramecium. Cover: Anne Aubusson-Fleury /Centre de Génétique Moléculaire Gif-sur-Yvette.

Editorial

  • A project that aims to mutate every gene in the mouse genome to improve our knowledge of mouse biology should help to avoid irreproducible results and costly failures in drug development.

    Editorial

    Advertisement

  • A US push to flag foods as genetically engineered is hard to swallow.

    Editorial
  • The discovery of a Wolf-Rayet supernova rebuts the idea that the biggest stars go quietly.

    Editorial
Top of page ⤴

World View

Top of page ⤴

Research Highlights

Top of page ⤴

Seven Days

  • The week in science: Chinese research agencies announce open-access policies; Russia severs space-science ties with the United States; and the Colorado River flows to the sea for the first time in 20 years.

    Seven Days
Top of page ⤴

News

Top of page ⤴

Correction

Top of page ⤴

News Feature

Top of page ⤴

Comment

Top of page ⤴

Correction

Top of page ⤴

Books & Arts

  • Sarah S. Richardson relishes a study of how nineteenth-century US feminists used the biologist's ideas.

    • Sarah S. Richardson
    Books & Arts
Top of page ⤴

Correspondence

Top of page ⤴

Obituary

Top of page ⤴

News & Views

  • Progeny of the protist Paramecium tetraurelia always retain the parental mating type. This inheritance is revealed to result from an RNA-guided DNA-deletion pathway that protects the genome from foreign DNA sequences. See Article p.447

    • Douglas L. Chalker
    News & Views
  • The probable signature of an ageing massive star's stellar wind has been detected shortly after the star underwent a supernova explosion. The finding suggests that such windy stars can have bright, observable deaths. See Letter p.471

    • John J. Eldridge
    News & Views
  • Two aspects of the blood–brain barrier — the transport of lipids to the brain and the transport of molecules across cells lining blood vessels — have been shown to be regulated by the same protein, Mfsd2a. See Letters p.503 & p.507

    • Christer Betsholtz
    News & Views
  • Porous materials called metal–organic frameworks hold promise for many applications, including molecular separations. One such material has been discovered that shape-shifts to amplify its selectivity for a target molecule.

    • Ryotaro Matsuda
    News & Views
  • Competition for access to a survival factor has been found to explain why incoming cells from the bone marrow replace resident cells in the thymus. Reducing this competition can cause tumours to form. See Article p.465

    • Eduardo Moreno
    News & Views
  • An analysis of crustal uplift around California's San Joaquin Valley, caused by groundwater extraction, reveals that such removal leads to both seasonal and long-term unclamping of the nearby San Andreas Fault system. See Letter p.483

    • Paul Lundgren
    News & Views
Top of page ⤴

Review Article

  • Cellular senescence has recently been shown to have roles in complex biological processes other than protection against cancer, and to represent a series of progressive and diverse cellular states after initial growth arrest; better understanding of mechanisms underlying its progression and of acute and chronic senescent cells may lead to new therapeutic strategies for age-related pathologies.

    • Jan M. van Deursen
    Review Article
Top of page ⤴

Article

  • The molecular basis for mating-type determination in the ciliate Paramecium has been elucidated, revealing a novel function for a class of small RNAs — these scnRNAs are typically involved in reprogramming the Paramecium genome during sexual reproduction by recognizing and excising transposable elements, but they are now found to be co-opted to switch off expression of the newly identified mating-type gene mtA by excising its promoter, and to mediate epigenetic inheritance of mating types across sexual generations.

    • Deepankar Pratap Singh
    • Baptiste Saudemont
    • Eric Meyer
    Article
  • Plasticity within neuronal microcircuits is believed to be the substrate of learning, and this study identifies two distinct disinhibitory mechanisms involving interactions between PV+ and SOM+ interneurons that dynamically regulate principal neuron activity in the amygdala and thereby control auditory fear learning.

    • Steffen B. E. Wolff
    • Jan Gründemann
    • Andreas Lüthi
    Article
  • T cells develop from thymic precursor cells that are constantly replaced with newly arriving bone marrow progenitor cells, and the ‘old’ and ‘new’ cells are shown here to compete; in the absence of cell competition, when the influx of new bone marrow progenitor cells is blocked, the old cells acquire the ability to self-renew and eventually become transformed, leading to the development of a form of leukaemia.

    • Vera C. Martins
    • Katrin Busch
    • Hans-Reimer Rodewald
    Article
Top of page ⤴

Letter

Top of page ⤴

Feature

Top of page ⤴

Career Brief

  • Administrative tasks gobble scientists' time, says report

    Career Brief
  • Prize winners invest their money in postdoc endowment

    Career Brief
  • Scientists will soon need to understand the language of many disciplines and sectors

    Career Brief
Top of page ⤴

Futures

  • An experimental direction.

    • John Frizell
    Futures
Top of page ⤴
Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing

Search

Quick links