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.

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 July 25, 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 July 25, 2014).

Share This




More Plants & Animals News

Friday, July 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Boy Attacked by Shark in Florida

Boy Attacked by Shark in Florida

Reuters - US Online Video (July 24, 2014) — An 8-year-old boy is bitten in the leg by a shark while vacationing at a Florida beach. Linda So reports. Video provided by Reuters
Powered by NewsLook.com
Goma Cheese Brings Whiff of New Hope to DRC

Goma Cheese Brings Whiff of New Hope to DRC

Reuters - Business Video Online (July 24, 2014) — The eastern region of the Democratic Republic of Congo, mainly known for conflict and instability, is an unlikely place for the production of fine cheese. But a farm in the village of Masisi, in North Kivu is slowly transforming perceptions of the area. Known simply as Goma cheese, the Congolese version of Dutch gouda has gained popularity through out the region. Ciara Sutton reports. Video provided by Reuters
Powered by NewsLook.com
Tyrannosaur Pack-Hunting Theory Aided By New Footprints

Tyrannosaur Pack-Hunting Theory Aided By New Footprints

Newsy (July 24, 2014) — A new study claims a set of prehistoric T-Rex footprints supports the theory that the giant predators hunted in packs instead of alone. Video provided by Newsy
Powered by NewsLook.com
Bill Gates: Health, Agriculture Key to Africa's Development

Bill Gates: Health, Agriculture Key to Africa's Development

AFP (July 24, 2014) — Health and agriculture development are key if African countries are to overcome poverty and grow, US software billionaire Bill Gates said Thursday, as he received an honourary degree in Ethiopia. Duration: 00:36 Video provided by AFP
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:
from the past week

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