Featured Research

from universities, journals, and other organizations

New type of heredity described in Paramecia, linked to epigenetics

Date:
May 9, 2014
Source:
CNRS (Délégation Paris Michel-Ange)
Summary:
Considered as an obsolete theory for many years, the transmission of acquired traits has returned to the forefront of debate thanks to the development of epigenetic research. In this context, a team of researchers has described how in Paramecia, mating types are transmitted from generation to generation through an unexpected mechanism. A Paramecium can acquire a new mating type that will be inherited by its progeny without any genetic modification being involved.

Considered as an obsolete theory for many years, the transmission of acquired traits has returned to the forefront of debate thanks to the development of epigenetic research. In this context, a team from the Institut de biologie at the Ecole normale supérieure (CNRS/ENS/INSERM)2 has described how in Paramecia, mating types are transmitted from generation to generation through an unexpected mechanism. These types are not determined by the genome sequence but by small RNA sequences transmitted via the maternal cytoplasm, which specifically inactivate certain genes during development. A Paramecium can thus acquire a new mating type that will be inherited by its progeny without any genetic modification being involved. Published in Nature on May 7, 2014, this work highlights a novel mechanism that may be governed by natural selection, thus allowing the evolution of species.

Related Articles


Paramecia, single-cell eukaryote organisms, are hermaphrodite: during their sexual reproduction (or conjugation), the partners exchange their genetic material. Paramecia nevertheless have two "mating types," called E and O. Conjugation can only occur between different mating types. As early as the 1940s, scientists such as Tracy Sonneborn had noted that mating type was not transmitted to progeny in Mendelian fashion: a new type of trait transmission, not dependent on the chromosomes, had to be involved, but they did not succeed in elucidating it.

Today, the team led by Éric Meyer at the ENS Institut de biologie has described the mechanism underlying this alternative heredity. To achieve this, they first showed that the difference between the E and O mating types was due to a transmembrane protein called mtA. Although its encoding gene is present in both types, it is only expressed in E individuals. The scientists then revealed the mechanism by which this gene is inactivated in type O individuals.

Paramecia have two nuclei: a germinal micronucleus that is transmitted during sexual reproduction and a somatic macronucleus -- resulting from the latter -- where the cell's genes are expressed. The mechanism for the transmission of mating types is based on small RNA, called scnARN, which are produced during meiosis. The original function of these RNA is to eliminate from the macronucleus a whole series of genetic sequences called transposable elements, which, like introns, have been introduced into the genes during evolution. As a first step, the scnARN scan the maternal macronucleus in order to identify the sequences that were deleted in the previous generation, and then make the same rearrangements in the new macronucleus. However, unexpectedly, this genome "cleaning" mechanism also allows the cell to silence functional genes. In type O individuals of Paramecium tetraurelia, scnARN eliminate the mtA gene promoter, thus deleting its expression. Thus, it is through the scnARN inherited from the maternal cytoplasm, and not from a particular gene sequence, that the mating type of Paramecium is defined.

This silencing process could in principle affect any gene. Thus in theory, Paramecia could transmit to their sexual progeny infinitely variable versions of the macronuclear genome from the same germline. As with genetic heredity, this mechanism may cause errors that might occasionally endow progeny with a selective advantage. In other words, the somatic macronucleus genome of Paramecium may evolve continuously, and in certain cases allow a short-term adaptation to changes in environmental conditions. And this can occur without any genetic mutations being involved. This type of Lamarckian heredity may thus offer a hitherto unsuspected lever for natural selection.


Story Source:

The above story is based on materials provided by CNRS (Délégation Paris Michel-Ange). Note: Materials may be edited for content and length.


Journal Reference:

  1. Deepankar Pratap Singh, Baptiste Saudemont, Gérard Guglielmi, Olivier Arnaiz, Jean-François Goût, Malgorzata Prajer, Alexey Potekhin, Ewa Przybòs, Anne Aubusson-Fleury, Simran Bhullar, Khaled Bouhouche, Maoussi Lhuillier-Akakpo, Véronique Tanty, Corinne Blugeon, Adriana Alberti, Karine Labadie, Jean-Marc Aury, Linda Sperling, Sandra Duharcourt, Eric Meyer. Genome-defence small RNAs exapted for epigenetic mating-type inheritance. Nature, 2014; DOI: 10.1038/nature13318

Cite This Page:

CNRS (Délégation Paris Michel-Ange). "New type of heredity described in Paramecia, linked to epigenetics." ScienceDaily. ScienceDaily, 9 May 2014. <www.sciencedaily.com/releases/2014/05/140509125957.htm>.
CNRS (Délégation Paris Michel-Ange). (2014, May 9). New type of heredity described in Paramecia, linked to epigenetics. ScienceDaily. Retrieved November 27, 2014 from www.sciencedaily.com/releases/2014/05/140509125957.htm
CNRS (Délégation Paris Michel-Ange). "New type of heredity described in Paramecia, linked to epigenetics." ScienceDaily. www.sciencedaily.com/releases/2014/05/140509125957.htm (accessed November 27, 2014).

Share This


More From ScienceDaily



More Plants & Animals News

Thursday, November 27, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Classic Hollywood Memorabilia Goes Under the Hammer

Classic Hollywood Memorabilia Goes Under the Hammer

Reuters - Entertainment Video Online (Nov. 26, 2014) — The iconic piano from "Casablanca" and the Cowardly Lion suit from "The Wizard of Oz" fetch millions at auction. Sara Hemrajani reports. Video provided by Reuters
Powered by NewsLook.com
Pet Dogs to Be Used in Anti-Ageing Trial

Pet Dogs to Be Used in Anti-Ageing Trial

Reuters - Innovations Video Online (Nov. 26, 2014) — Researchers in the United States are preparing to discover whether a drug commonly used in human organ transplants can extend the lifespan and health quality of pet dogs. Video provided by Reuters
Powered by NewsLook.com
From Popcorn To Vending Snacks: FDA Ups Calorie Count Rules

From Popcorn To Vending Snacks: FDA Ups Calorie Count Rules

Newsy (Nov. 25, 2014) — The US FDA is announcing new calorie rules on Tuesday that will require everywhere from theaters to vending machines to include calorie counts. Video provided by Newsy
Powered by NewsLook.com
Feast Your Eyes: Lamb Chop Sent Into Space from UK

Feast Your Eyes: Lamb Chop Sent Into Space from UK

Reuters - Light News Video Online (Nov. 25, 2014) — Take a stab at this -- stunt video shows a lamb chop's journey from an east London restaurant over 30 kilometers into space. Rough Cut (no reporter narration). Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins