{"id":136144,"date":"2010-06-19T13:22:39","date_gmt":"2010-06-19T12:22:39","guid":{"rendered":"http:\/\/www.madrimasd.org\/blogs\/universo\/?p=136144"},"modified":"2010-06-19T13:31:00","modified_gmt":"2010-06-19T12:31:00","slug":"la-vida-reticulada-una-nueva-genetica-de-la-biosfera","status":"publish","type":"post","link":"https:\/\/www.madrimasd.org\/blogs\/universo\/2010\/06\/19\/136144","title":{"rendered":"La Vida Reticulada. Una Nueva Gen\u00e9tica de la Biosfera"},"content":{"rendered":"

\u00bfSabe usted lo que contienen sus genes? \u00bfSon de mam\u00e1 y de pap\u00e1, exclusivamente? Pues va a ser que no<\/strong><\/span>. Posiblemente su genoma pueda albergar DNA<\/span><\/strong> de virus, bacterias, hongos, insectos y de algunos otros bichos par\u00e1sitos<\/span> <\/strong>que infectaron a sus progenitores, m\u00e1s o menos ancestrales, aunque tambi\u00e9n de simbiontes<\/strong>.<\/span> El ideal neodarvinista de la herencia vertical, como motor de la evoluci\u00f3n biol\u00f3gica, parece desmoronarse. La vida probablemente deba analizarse como una ret\u00edcula o red de intercambio del material hereditario. Ser\u00eda algo as\u00ed como<\/span><\/strong> la estructura de Internet, con grandes autopistas jer\u00e1rquicas de herencia vertical y peque\u00f1os atajos entre ellas de otra de naturaleza horizontal. Y eso fundamentalmente en los seres superiores o eucariotas, por cuanto en el mundo de los procariontes tal jerarqu\u00eda se difumina, incluso podr\u00eda diluirse por completo. D\u00eda a d\u00eda, se van descubriendo m\u00e1s casos de la transferencia horizontal de genes entre los taxa m\u00e1s dispares.<\/p>\n

\"la-evolucion-seria-algo-asi-pero-tambien-entre-las-pequenas-ramas-del-arbol-de-la-vida-y-entenderse-como-una-red-tanto-o-mas-que-como-un-arbol-fuente-genome-anatomies-thumb\"\u00a0<\/p>\n

La evoluci\u00f3n ser\u00eda algo as\u00ed, pero tambi\u00e9n entre las peque\u00f1as ramas del \u00e1rbol de la vida, que de este modo puede entenderse como una red tanto o m\u00e1s que como un \u00e1rbol. Fuente: Genome anatomies<\/a><\/p>\n

\u00a0<\/p>\n

\u00a0Sab\u00edamos que ciertos segmentos de virus se insertan en nuestro genoma, o que este tipo de herencia es com\u00fan en el mundo microbiano procari\u00f3tico. Hace pocas semanas ya os anunciamos en otro post como los hongos, organismos eucariotas, pueden llegar a trasferirse horizontalmente entre taxa distintos cromosomas enteros. Investigaciones recientes dicen haber comprobado la presencia del mismo mecanismo (en este caso genes) entre par\u00e1sitos y mam\u00edferos. Incluso ciertos insectos parecen sintetizar compuestos esenciales, que solo se cre\u00eda posible que lo hicieran vegetales y hongos, gracias a que estos \u00faltimos les han regalado las secuencias necesarias de DNA.\u00a0\u00a0<\/p>\n

Sabe usted lo que son los tranposones o genes saltarines<\/a>. Es una parte de este rompecabezas, aunque hay mucho m\u00e1s que tener en cuenta. Como defienden los autores de uno de los estudios que abajo os incluimos, cuando se descubre en nuevo mecanismo puede parecernos como algo extraordinario, singular o extremadamente raro. Sin embargo, abre la puerta a que otros cient\u00edficos urgen en tales rarezas, terminando por percatarse que resultan ser de lo m\u00e1s ubicuo. De momento, los simbiontes y par\u00e1sitos parecen estar en buena posici\u00f3n de la parrilla de salida de tales tipos de transferencias hereditarias, a las que algunos llamar\u00e1n, con mala intenci\u00f3n, \u201cinterferencias\u201d. Y as\u00ed la estructura de su genoma cambia y como corolario sus cauces evolutivos<\/span><\/strong>. Esta perspectiva es acusadamente distinta de la que defiende la ortodoxia darvinista.<\/p>\n

No os voy a desmenuzar las noticias que os muestro abajo en suahili<\/em>, sino que intentar\u00e9 tan solo explicar su contenido en forma de met\u00e1fora.<\/p>\n

\u00a0\"la-vida-reticulada-fuente-panda-s-thumb\"<\/p>\n

La vida Reticulada. Fuente: Panda\u2019s Thumb<\/a><\/p>\n

\u00a0En el mundo de los microorganismos procariotas<\/span><\/strong>, cada vez resulta m\u00e1s evidente que la herencia es tanto vertical como horizontal, a modo de una red en que las carreteras son m\u00e1s o menos de igual anchura. En los eucariotas<\/span><\/strong>, y especialmente conforme aumenta su complejidad, la herencia vertical<\/span><\/strong> (de padres a hijos) deviene en dominante<\/span><\/strong>. De hecho, la ortodoxia neodarviniana nos dice que es exclusiva. \u00a0Empero la vida se salta a la torera reglas tan ramplonas. La herencia vertical ser\u00eda algo as\u00ed como grandes autopistas independientes por donde circulan la mayor parte de los genes<\/span><\/strong> de los individuos, generaci\u00f3n tras generaci\u00f3n. Sin embargo, de vez en cuando, algunos toman un atajo vertiendo parte de su material en otra autopista<\/strong> por carreteras o caminos vecinales<\/strong><\/span>. La pregunta del mill\u00f3n es averiguar la frecuencia con la que acaece tal evento. Sabemos que no parece ser muy usual, aunque var\u00eda entre las diferentes formas de vida. Sin embargo, lo realmente intrigante es hasta que punto tal \u201cdiversi\u00f3n\u201d modifica la evoluci\u00f3n de las especies<\/span><\/strong>, ya que el tema no resulta ser tanto de cantidad como de calidad o importancia.<\/p>\n

Volvemos a reiterar que la historia de las ciencias nos ense\u00f1a que, cuando se abre una nueva v\u00eda mediante un descubrimiento inesperado, detr\u00e1s puede llegar un torrente que modifica dr\u00e1sticamente el paisaje cient\u00edfico anterior. El tiempo dir\u00e1. Personalmente tengo la impresi\u00f3n que el neodarvinismo, tal como lo defienden sus ultraortodoxos califas, tiene los d\u00edas contados.<\/p>\n

\u00a0Juan Jos\u00e9 Ib\u00e1\u00f1ez \u00a0<\/strong><\/span><\/p>\n

\u00a0<\/strong>Ver tambi\u00e9n el post <\/strong><\/p>\n

La Extraordinaria Gen\u00e9tica de los Microorganismos del Suelo<\/a><\/p>\n

Scientists Uncover Transfer of Genetic Material Between Blood-Sucking Insect and Mammals<\/a><\/strong><\/p>\n

ScienceDaily (Apr. 30, 2010)<\/span><\/strong> \u2014 Researchers at The University of Texas at Arlington have found the first solid evidence of horizontal DNA transfer, the movement of genetic material among non-mating species, between parasitic invertebrates and some of their vertebrate hosts<\/span><\/strong>.<\/p>\n

The findings are published in the April 28 issue of the journal Nature<\/strong><\/span>, one of the world’s foremost scientific journals.<\/p>\n

Genome biologist C\u00e9dric Feschotte and postdoctoral researchers Cl\u00e9ment Gilbert and Sarah Schaack found evidence of horizontal transfer of transposon from a South American blood-sucking bug and a pond snail to their hosts<\/strong>. A transposon is<\/strong> a segment of DNA that can replicate itself and move around to different positions within the genome. Transposons can cause mutations, change the amount of DNA in the cell and dramatically influence the structure and function of the genomes where they reside<\/strong>.<\/p>\n

\u00abSince these bugs frequently feed on humans, it is conceivable that bugs and humans may have exchanged DNA<\/strong> through the mechanism we uncovered. Detecting recent transfers to humans would require examining people that have been exposed to the bugs for thousands of years, such as native South American populations,\u00bb Feschotte said.<\/p>\n

Data on the insect and the snail provide strong evidence for the previously hypothesized role of host-parasite interactions in facilitating horizontal transfer of genetic material<\/strong>. Additionally, the large amount of DNA generated by the horizontally transferred transposons supports the idea that the exchange of genetic material between hosts and parasites influences their genomic evolution<\/strong>.<\/p>\n

\u00abIt’s not a smoking gun, but it is as close to it as you can get,\u00bb Feschotte said. he infected blood-sucking triatomine, causes Chagas disease by passing trypanosomes (parasitic protozoa) to its host<\/strong>. Researchers found the bug shared transposon DNA with some hosts, namely the opossum and the squirrel monkey. The transposons found in the insect are 98 percent identical to those of its mammal hosts<\/strong>.<\/p>\n

The researchers also identified members of what Feschotte calls space invader transposons in the genome of Lymnaea stagnalis, a pond snail that acts as an intermediate host for trematode worms, a parasite to a wide range of mammals<\/strong>.<\/p>\n

The long-held theory is that mammals obtain genes vertically, or handed down from parents to offspring<\/strong>. Bacteria receive their genes vertically and also horizontally, passed from one unrelated individual to another or even between different species. Such lateral gene transfers are frequent in bacteria and essential for rapid adaptation to environmental and physiological challenges, such as exposure to antibiotics<\/strong>.<\/p>\n

Until recently, it was not known horizontal transfer could propel the evolution of complex multicellular organisms like mammals<\/strong>. In 2008, Feschotte and his colleagues published the first unequivocal evidence of horizontal DNA transfer.<\/p>\n

Millions of years ago, tranposons jumped sideways into several mammalian species<\/strong>. The transposon integrated itself into the chromosomes of germ cells, ensuring it would be passed onto future generations<\/strong>. Thus, parts of those mammals’ DNA did not descend from their common ancestors, but were acquired laterally from another species<\/strong>.<\/p>\n

The actual means by which transposons can spread across widely diverse species has remained a mystery<\/strong>.<\/p>\n

\u00abWhen you are trying to understand something that occurred over thousands or millions of years ago, it is not possible to set up a laboratory experiment to replicate what happened in nature,\u00bb Feschotte said.<\/p>\n

Instead, the researchers made their discovery using computer programs designed to compare the distribution of mobile genetic elements among the 102 animals for which entire genome sequences are currently available. Paul J. Brindley of George Washington University Medical Center in Washington, D.C., contributed tissues and DNA used to confirm experimentally the computational predictions of Feschotte’s team.<\/p>\n

When the human genome was sequenced a decade ago, researchers found that nearly half of the human genome is derived from transposons, so this new knowledge has important ramifications for understanding the genetics of humans and other mammals<\/strong>.<\/p>\n

Feschotte’s research is representative of the cutting edge research that is propelling UT Arlington on its mission of becoming a nationally recognized research institution.<\/p>\n

Story Source: Adapted from materials provided by University of Texas at Arlington<\/a>.<\/p>\n

Journal Reference<\/strong>: Cl\u00e9ment Gilbert, Sarah Schaack, John K. Pace II, Paul J. Brindley, C\u00e9dric Feschotte. A role for host-parasite interactions in the horizontal transfer of transposons across phyla. Nature, 2010; 464 (7293): 1347 DOI: 10.1038\/<\/a><\/p>\n

\u00a0<\/p>\n

First Case of Animals Making Their Own Essential Nutrients: Carotenoids<\/a><\/strong><\/p>\n

ScienceDaily (<\/strong>Apr. 30, 2010<\/strong>)<\/strong> \u2014 The insects known as aphids can make their own essential nutrients called carotenoids<\/strong>, according to University of Arizona researchers.<\/p>\n

No other animals are known to make the potent antioxidants. Until now scientists thought the only way animals could obtain the orangey-red compounds was from their diet.<\/p>\n

\u00abIt is written everywhere that animals do not make carotenoids<\/strong>,\u00bb said Nancy Moran, leader of the UA team that overturned the conventional wisdom.<\/p>\n

Carotenoids are<\/strong> building blocks for molecules crucial for vision, healthy skin, bone growth and other key physiological functions. Beta-carotene, the pigment that makes carrots orange, is the building block for Vitamin A<\/strong>.<\/p>\n

\u00abOnce you start realizing how widespread carotenoids are, you realize that they’re everywhere in life,\u00bb said Moran, a UA Regents’ Professor of ecology and evolutionary biology.<\/p>\n

\u00abThe yellow color in egg yolks, the pink in shrimp and salmon, the pink in flamingos, tomatoes, carrots, peppers, Mexican poppies, marigolds — the yellow, orange, and red are all carotenoids.\u00bb<\/p>\n

Moran and her co-author Tyler Jarvik also figured out how the aphids they studied, known as pea aphids, acquired the ability to make carotenoids. \u00abWhat happened is a fungal gene got into an aphid and was copied<\/strong>,\u00bb Moran said. She added that, although gene transfers between<\/strong> microorganisms are common, finding a functional fungus gene as part of an animal’s DNA is a first.<\/strong><\/p>\n

\u00abAnimals have a lot of requirements that reflect ancestral gene loss. This is why we require so many amino acids and vitamins in the diet,\u00bb she said. \u00abUntil now it has been thought that there is simply no way to regain these lost capabilities. But this case in aphids shows that it is indeed possible to acquire the capacity to make needed compounds.<\/strong><\/p>\n

\u00abPossibly this will be an extraordinarily rare case. But so far in genomic studies, a single initial case usually turns out to be only an example of something more widespread<\/strong>.\u00bb<\/p>\n

She and Jarvik, a research specialist in UA’s department of chemistry and biochemistry, report their discovery in the paper, \u00abLateral Transfer of Genes from Fungi Underlies Carotenoid Production in Aphids,\u00bb to be published in the April 30 issue of the journal Science<\/strong>. The National Science Foundation funded the research.<\/p>\n

A lucky accident in the lab plus the recent sequencing of the pea aphid genome made the discovery possible, Moran said.<\/p>\n

Pea aphids, known to scientists as Acyrthosiphon pisum, are either red or green. Aphids are clonal<\/strong> — the mothers give birth to daughters that are genetically identical to their mothers. So when an aphid in the Moran lab’s red 5A strain began giving birth to yellowish-green babies, Moran and her colleagues knew they were looking at the results of a mutation.<\/p>\n

\u00abWe named it 5AY for yellowish,\u00bb she said. \u00abThat yellowish mutant happened in 2007. We just kept the strain as a sort of pet in the lab. I figured that one day we’d figure out how that happened.\u00bb<\/p>\n

Symbiotic bacteria live within aphids in specialized cells. The bacteria, which are passed from mother to babies, supply the insects with crucial nutrition. If their bacteria die, the aphids die<\/strong>.<\/p>\n

Moran, who has been studying the pea aphid-bacteria system for decades, already knew the three main species of symbiotic bacteria did not make carotenoids.<\/p>\n

She also was pretty sure the aphids didn’t get their carotenoids from their diet.<\/strong> Aphids eat by sucking the phloem sap from plants, but the sap is carotenoid-poor. In addition, the carotenoids in the aphids were different from those usually found in plants. In late 2009, after the complete DNA sequence of the pea aphid became available to researchers, she decided to search it for carotenoid genes.<\/p>\n

All organisms use the same biosynthetic pathway to make carotenoids, which made searching for carotenoid genes straightforward, she said.<\/p>\n

Lucky for Moran, the researchers who sequenced the pea aphid genome used red aphids, which have an extra copy of the carotenoid gene, making the gene causing the red color easier to find.<\/p>\n

Next, she figured out whether the genes were from pea aphid DNA or from uncommon symbiotic bacteria or were just contamination from fungi in the sample.<\/p>\n

In the laboratory, Moran and Jarvik found eliminating the symbiotic bacteria from a strain of aphids did not change the color of the offspring, meaning the symbiotic bacteria were not the source of the red color<\/strong>.<\/p>\n

In addition, tracing the lineages of the red, green and yellow strains of aphids showed the colors had a Mendelian inheritance pattern, indicating the DNA that coded for red was part of the aphid’s DNA<\/strong>.<\/p>\n

That inheritance pattern also fit with another team’s research that suggested both colors were present in nature because red aphids are more susceptible to parasitic wasps<\/strong>, whereas green aphids are more susceptible to predators such as lady-bird beetles.<\/p>\n

The final piece of the puzzle was figuring out where the genes came from. The particular sequence of aphid DNA that coded for carotenoids differed from bacterial carotenoid genes and matched those from some fungi<\/strong>.<\/p>\n

Moran said a long-term association between aphids and pathogenic fungi could make such a gene transfer possible<\/strong>.<\/p>\n

The discovery illustrates \u00abthe interweaving of organisms and their genomes over time and their merging in different ways,\u00bb she said. \u00abThe distinctness of different genomes and organisms and lineages is much less than we thought.<\/strong>\u00ab<\/p>\n

Story Source: Adapted from materials provided by University of Arizona<\/a>. Original article written by Mari N. Jensen.<\/p>\n

Journal Reference:Nancy<\/strong> A. Moran and Tyler Jarvik. Lateral Transfer of Genes from Fungi Underlies Carotenoid Production in Aphids. Science, 30 April 2010 328: 624-627 DOI: 10.1126\/science.1187113<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

\u00bfSabe usted lo que contienen sus genes? \u00bfSon de mam\u00e1 y de pap\u00e1, exclusivamente? Pues va a ser que no. Posiblemente su genoma pueda albergar DNA de virus, bacterias, hongos, insectos y de algunos otros bichos par\u00e1sitos que infectaron a sus progenitores, m\u00e1s o menos ancestrales, aunque tambi\u00e9n de simbiontes. El ideal neodarvinista de la herencia vertical, como motor de la evoluci\u00f3n biol\u00f3gica, parece desmoronarse. La vida probablemente deba analizarse como una ret\u00edcula o red de intercambio del material hereditario. Ser\u00eda algo as\u00ed como la estructura de Internet, con grandes autopistas jer\u00e1rquicas de herencia vertical y peque\u00f1os atajos entre ellas\u2026<\/p>\n","protected":false},"author":26,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"ngg_post_thumbnail":0},"categories":[1],"tags":[],"blocksy_meta":{"styles_descriptor":{"styles":{"desktop":"","tablet":"","mobile":""},"google_fonts":[],"version":4}},"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/posts\/136144"}],"collection":[{"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/users\/26"}],"replies":[{"embeddable":true,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/comments?post=136144"}],"version-history":[{"count":12,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/posts\/136144\/revisions"}],"predecessor-version":[{"id":136468,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/posts\/136144\/revisions\/136468"}],"wp:attachment":[{"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/media?parent=136144"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/categories?post=136144"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/tags?post=136144"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}