Nav: Home

Parasitic nematodes that cause greatest agricultural damage abandoned sex

June 09, 2017

The nematode worms that cause the world's most devastating crop losses have given up on sexual reproduction and instead rely on their large, duplicated genomes to thrive in new environments. A group led by Etienne G. J. Danchin of the French National Institute for Agricultural Research (INRA) report these findings in a new study published June 8, 2017 in PLOS Genetics.

While most animals - more than 99 percent - find that a sexual lifestyle is the best path for evolutionary success, certain root-knot nematode species can only reproduce without sex. Instead of hitting an evolutionary dead-end, these plant pests have a wider geographic range and can infect greater numbers of crops than sexual species. To investigate the reasons behind their success, researchers sequenced and assembled the genomes of the three most damaging root-knot nematodes and compared them to a sexual relative. The asexual genomes are large, with numerous duplicated regions resulting from past reproduction events where at least two individual genomes recently hybridized together. Further analysis showed that many of the gene copies had each evolved different sequences and functions. Besides these gene copies, the genomes of the asexual nematodes are rich in transposable elements, DNA segments that are able to move and multiply in genomes. These elements could provide genomic plasticity and have functional consequences too. The researchers suspect that the asexual nematodes' unusual hybrid genome structure has helped them to successfully adapt to a wide range of environments, even in the absence of sex.

These findings challenge the prevailing idea that sexual species will always outcompete their asexual relatives and may even have wider implications for our understanding of why sex evolved. The work also supports the existing idea that hybridization is an evolutionary phenomenon capable of giving rise to new parasites and infectious organisms. For plant breeders, a greater understanding of these economically significant parasites can potentially help in the breeding of better plant varieties that can resist nematode attacks and reduce crop losses.

Etienne G. J. Danchin adds: "For a long time, the root-knot nematodes have remained an evolutionary puzzle because the most devastating agricultural parasites are those that have abandoned sex and meiosis. Being unable to combine beneficial mutations from different individuals and unable to purge progressive accumulation of deleterious mutations, they are expected to represent evolutionary dead ends. By analyzing and comparing their genomes, we provide large-scale evidence that these asexual nematodes underwent hybridization and are polyploid. Their duplicated hybrid genome architectures provide these nematodes with multi-copy genes showing diverged sequence and expression patterns where their sexual relatives have very closely related alleles. We suspect these multiple copies provide a reservoir to adapt to different environments and plant hosts, and constitute an evolutionary advantage over their sexual relatives (at least in the short term). Their intriguing parasitic success despite absence of sex could thus be due to their hybrid origin where they combined multiple genomes of adapted parasitic nematodes in one single species.

It is now important to understand how these hybrids have emerged and whether the same conditions could favor emergence of even more aggressive and devastating new hybrids."
In your coverage please use this URL to provide access to the freely available article in PLOS Genetics:

Citation: Blanc-Mathieu R, Perfus-Barbeoch L, Aury J-M, Da Rocha M, Gouzy J, Sallet E, et al. (2017) Hybridization and polyploidy enable genomic plasticity without sex in the most devastating plant-parasitic nematodes. PLoS Genet 13(6): e1006777.

Funding: This work was supported by the Agence Nationale de la Recherche program ANR-13-JSV7-0006 - ASEXEVOL, the INRA program AAP SPE 2011, as well as Université de Nice Sophia-Antipolis Postdoc program 2013-2014. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing Interests: The authors have declared that no competing interests exist.


Related Nematodes Articles:

Otherworldly worms with three sexes discovered in Mono Lake
The extreme environment of Mono Lake was thought to only house two species of animals -- until now.
New information on regulation of sense of smell with the help of nematodes
PIM kinases are enzymes that are evolutionarily well conserved in both humans and nematodes.
In worms, researchers uncover protein that may one day make opioid use safer
Studying mutant worms has led to the discovery of a receptor that reduces sensitivity to opioid side effects in these organisms.
New study shows how climate change could affect impact of roundworms on grasslands
The researchers found in extreme drought conditions that predator nematodes significantly decreased, which led to the growth of root-feeding nematodes.
Study shows how the nervous system can transmit information across multiple generations
A new Tel Aviv University study reveals how the nervous system can transmit information across multiple generations.
More Nematodes News and Nematodes Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Erasing The Stigma
Many of us either cope with mental illness or know someone who does. But we still have a hard time talking about it. This hour, TED speakers explore ways to push past — and even erase — the stigma. Guests include musician and comedian Jordan Raskopoulos, neuroscientist and psychiatrist Thomas Insel, psychiatrist Dixon Chibanda, anxiety and depression researcher Olivia Remes, and entrepreneur Sangu Delle.
Now Playing: Science for the People

#537 Science Journalism, Hold the Hype
Everyone's seen a piece of science getting over-exaggerated in the media. Most people would be quick to blame journalists and big media for getting in wrong. In many cases, you'd be right. But there's other sources of hype in science journalism. and one of them can be found in the humble, and little-known press release. We're talking with Chris Chambers about doing science about science journalism, and where the hype creeps in. Related links: The association between exaggeration in health related science news and academic press releases: retrospective observational study Claims of causality in health news: a randomised trial This...