The genome of the aphid Acyrthosiphon pisum

The genome of the aphid Acyrthosiphon pisum has been secuenciado for the International Consortium of the Genome of the Aphid (IAGC in his initials in English), a consortium formed by more than 50 groups of investigation of 16 countries.

The IAGC was created in Paris in June, 2003 to coordinate efforts and to promote the investigation on aphides to convert them into a biological reference model to molecular, cellular and biological scale at the same level as other insects it shaped whose genome has already been secuenciado.

Why A. pisum?

As other species that are part of the Project Genome of the Insects, the election of A. pisum has been based on his economic importance. This aphid is a parasite of leguminous plants that causes serious agricultural plagues and economic losses in the agriculture. The peculiarities of his vital cycle (rapid reproduction and existence of multiple forms) it turns him into a perfect model for studies on the interactions between plants and insects, symbiosis, vector of transmission of virus and genetic plasticity. It supports a symbiotic relation with the bacterium Buchnera aphidicola, which lives inside a few specializing cells through called bacteriocitos and with the one that has coevolved. Also, there is the first insect hemíptero (thumbtacks, cicadas and aphides) and the first one with partial metamorphosis (hemimetábolo) whose genome there is secuenciado.

Vital cycle of Acyrthosiphon pisum. During the spring and the summer, the females [F] reproduce asexualmente (parthenogenesis) giving place to a descent (females) áptera [To] or flutter [B] that also is reproduced asexualmente. The winged aphides, which can disperse to other plants, take place in conditions of overpopulation or stress. During the autumn, males take place ápteros and flutters of wings [D] and females ápteras [C] that are reproduced sexually and put eggs [And] that will give place in the spring to females ápteras [F]. The females they can be vivíparas (when the reproduction is asexual) and oviparous (when the reproduction is sexual).

Peculiarities of his genome

The sequence of the genome of A. pisum has given place to more than 30 scientific articles, many of them published in a special number of the magazine Insect Molecular Biology.

• A. Pisum has a genome haploide with approximately 464 million pairs of bases (nucleótidos), major than that of other insects, and four chromosomes. Although the article published in Plos Biology does not give a concrete number alleging that is necessary a more precise inventory, Stephen Richards, chief of the team that there is secuenciado the genome of the aphid, speech of 35.000 genes (the human genome has approximately 23.000), many of which are duplicated and others have no equivalence in other insects species.
• The genomes of A. pisum and B. aphidicola they are coordinated. Some metabolic routes are shared, the genome of the aphid presents genes of bacterial origin and the bacterium synthesizes nine amino acids that the aphid can neither produce also do not even nor obtain across his diet.
• Several genes of the immune system are absent, specifically those of the route IMD that they produce péptidos antibacterial like the cecropina and the defensina. This can be interpreted of two forms: the defenses absence opposite to bacterial infections could facilitate the symbiosis with bacteria or that his rapid reproductive cycle and his feeding (sap of plants) frees from bacteria diminished the selective pressure to support a costly immune system.
• Like herbivorous animal, it possesses an enzymes arsenal destoxificadoras. Nevertheless, his number is minor than, for example, the fruit fly, the mosquito Anopheles or the red beetle of the flour and major than that of the bee melífera.
• The peculiar vital cycle of the aphides, which alternates forms vivíparas with oviparous and winged forms with ápteras, can be facilitated by duplications in many genes related to his development.

Genome Sequence of the Pea Aphid Acyrthosiphon pisum The International Aphid Genomics Consortium. 2010. PLoS Biol 8 (2), e1000313. The International Aphid Genomics Consortium (2010). Genome Sequence of the Pea Aphid Acyrthosiphon pisum PLoS Biology, 8 (2) DOI: 10.1371/journal.pbio.1000313 AphidBase Base de datos of the genome of the aphid.

The bees can say: For!

When a bee worker melífera (Apis mellifera) finds a food source, it returns to the beehive and realizes a dance to report of the meal availability and to recruit his partners.

In certain occasions, it is possible to observe how a bee strikes his head against the body of the one that realizes the dance and expresses a short buzz. At first, to this sign it was named a request call because one believed that these clicks were serving so that the struck bee was providing a meal sample to him to the beating bee, but no meal transfer was taking place. Also it was thought that it might have some relation with feeding areas sobreexplotadas, although the sign also was taking place in areas where there were no many bees.

For!. The bee that does the dance (in the center and with the yellow point in the thorax) stops when the bee marked with a S in the thorax gives him a click with the head.

The group of James C. Nieh, in the Section of Ecology, Behavior and Evolution of the Division of Biological Sciences of the University of California in San Diego, has demonstrated that in fact it is a sign of stop to warn that the pecoreo place is not suitable or is dangerous. The bees transmit the sign to partners who have visited the same meal source and are treating ―con his dance ― of recruiting other workers towards this place. The message that they transmit comes to mean Stops dancing and asking for reinforcements because that place is already not worth it and takes place when they worsen the conditions in which the bees look for meal, good because it remains small in the pecoreo place or because there are predators.

In a few experiments in which there were simulated attacks of chandeliers crab and of bees of other colonies, it was observed that the production of signs of stop was increasing between 43 and 88 times, being the negative answer (number of signs of stop) major when there was some type of physical aggression or the more dangerous the attack was.

The bee is the second species of social insect where a negative sign is observed. The case that had been studied in advance was that of the ant Pharaoh (Monomorium pharaonis), who uses a repellent pheromone to mark a way that it is not necessary to continue for being dangerous or lacking interest.

If we think to the social insects how a superorganism where the division of labor is specializing and where every individual of the group acts cooperatively and is unable to survive isolated during long periods of time, the positive and negative signs remember, in certain way, to that they express the cells to communicate between themselves.

To Negative Feedback Signal That Is Triggered by Peril Curbs Honey Bee Recruitment James C. Nieh. 2010. Cur. Biol. 20 (4), pp. 310-315. Nieh, J. (2010). To Negative Feedback Signal That Is Triggered by Peril Curbs Honey Bee Recruitment Current Biology, 20 (4), 310-315 DOI: 10.1016/j.cub.2009.12.060

The genome of the wasp parasitoide Nasonia

Nasonia is a wasps genre parasitoides that comprises four related species (N. vitripennis, N. giraulti, N. longicornis and N. oneida). There are insects of tiny size (2-3 millimeters) that put his eggs in the cold sores of several species of flies.

The Group of Work of the Genome of Nasonia, an international consortium formed by 157 investigators of 13 countries led by John H. Werren, teacher of biology in Universiad de Rochester, and Stephen Richards, of the Center of Sequence of the Human Genome in Baylor College of Medicine, there is secuenciado the genome of three species of this himenóptero (N. vitripennis, N. giraulti and N. longicornis).

Why Nasonia?

The wasps parasitoides are insects which larvae parasitan several phases of the development of other arthropods. The females inject poison and put his eggs on or inside his guest and the larvae develop feeding on him until they kill it. The parasitoides are used usually for the biological control of plagues of insects and it is believed that there are approximately 600.000 species. Nasonia parasite several flies species and it is the second genre of himenópteros whose genome has been secuenciado (the first one was that of the bee). It has a period of development of two weeks and it is very prolific, easy to support in a laboratory and the crossing between species produces a fertile descent. All this turns Nasonia into a model for the study of the evolutionary genetics and of the development. Hence the importance of the sequence of his genome inside the Project Genome of the Insects, which will allow to study in depth the biology of the insects parasitoides and improve his utility for the biological control of plagues of agricultural and medical importance.

Peculiarities of his genome

The sequence of the genome of Nasonia has given place to a series of scientific articles that explore diverse facets of his biology at molecular level.

• The Nasonia genome is organized in five chromosomes with approximately 239,8 million pairs of bases and approximately 17.279 genes, 60 % of which it has counterparts in the human beings, 18 % is a specific of the arthropods, 2,4 % seems to be exclusive of the himenópteros and 12 % does not have homologías egg whites or it is a Nasonia only one.
• It contains a high number of repetitions of ADN and trasposones (sequences of ADN saltarinas capable of answering and of being inserted in a new place of a certain genome).
• The genome codifies all the enzymes necessary for the metilación of the ADN, a genetic modification related to the regulation of the genes in human beings and other vertebrates, although it stays away in insects as Drosophila. It stays for seeing if the metilación in Nasonia has the same regulatory functions as in vertebrates. In the bee, for example, the metilación of the ADN is related to the development of the castes and in Nasonia one believes that it has to do with the determination of the sex.
• Nasonia has the biggest number of genes yellow/mayor royal jelly (genes related to the formation of castes and the sociability) found in any insect. Although his function in Nasonia is not known, they express themselves in different textiles and phases of the development.
• The bacterium endosimbionte Wolbachia and some poxvirus have transferred his genes to the Nasonia genome. The horizontal transference (between not related organisms) of genes can be a mechanism to acquire new genes and functions.
• The carnivorous Nasonia diet has provoked a loss or reorganization of the metabolic routes of some amino acids.
• Nasonia has a finished arsenal of poisonous toxins. In contrast to the poison of the bee, which it causes necrosis and pain, the poisons of the parasitoides are subtler and they induce physiological changes in his guest like the detention of the development, suppression of the immune answer, induction of palsy, cellular death and alteration of the behavior. 79 possible toxins have been identified and close to the half they are not related to the toxins of the poison of other insects. These poisons might be useful for the pest control and the development of medicines.

Functional and Evolutionary Insights from the Genomes of Three Parasitoid Nasonia Species The Nasonia Genome Working Group. 2010. Science 327, pp. 343-348. The Nasonia Genome Working Group (2010). Functional and Evolutionary Insights from the Genomes of Three Parasitoid Nasonia Species Science, 327 (5963), 343-348 DOI: 10.1126/science.1178028 Web Werren Lab of the laboratory of John H. Werren with information about the biology of Nasonia. NasoniaBase Repository of information about the genome of Nasonia.