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Team:KU Leuven/Project/Aphid Background
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<img src="https://static.igem.org/mediawiki/2013/e/ee/Colored_aphids.jpg" alt="Aphid colors"/> | <img src="https://static.igem.org/mediawiki/2013/e/ee/Colored_aphids.jpg" alt="Aphid colors"/> | ||
<p>Figure 1ǀ Red, yellow-green and green pea aphids.</p> | <p>Figure 1ǀ Red, yellow-green and green pea aphids.</p> | ||
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| + | <h3>Synopsis</h3> | ||
| + | <p align="justify">During a long period of co-evolution, plants and aphids have established a complex interaction. On the one hand, aphids have established complex life cycles involving extensive phenotype plasticity with rapid population growth (Blackman and Eastop, 1984) and a very short generation time (Morrison and Peairs, 1998). On the other hand, plants have also evolved delicate and complicated defence systems comprising constitutive defence traits and defence pathways induced upon aphid attack (Chen 2008). Breeders and growers are still struggling to find an efficient strategy for aphid control in major crop plants, but the KU Leuven iGEM project has a answer to this problem. Our project consists of a genetically engineered bacteria that can reduce the aphid damage on a sustainable way by hacking into their communication system. | ||
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Revision as of 13:27, 30 August 2013
Secret garden
Congratulations! You've found our secret garden! Follow the instructions below and win a great prize at the World jamboree!
- A video shows that two of our team members are having great fun at our favourite company. Do you know the name of the second member that appears in the video?
- For one of our models we had to do very extensive computations. To prevent our own computers from overheating and to keep the temperature in our iGEM room at a normal level, we used a supercomputer. Which centre maintains this supercomputer? (Dutch abbreviation)
- We organised a symposium with a debate, some seminars and 2 iGEM project presentations. An iGEM team came all the way from the Netherlands to present their project. What is the name of their city?
Now put all of these in this URL:https://2013.igem.org/Team:KU_Leuven/(firstname)(abbreviation)(city), (loose the brackets and put everything in lowercase) and follow the very last instruction to get your special jamboree prize!
Aphid Biology 101
Figure 1ǀ Red, yellow-green and green pea aphids.
Synopsis
During a long period of co-evolution, plants and aphids have established a complex interaction. On the one hand, aphids have established complex life cycles involving extensive phenotype plasticity with rapid population growth (Blackman and Eastop, 1984) and a very short generation time (Morrison and Peairs, 1998). On the other hand, plants have also evolved delicate and complicated defence systems comprising constitutive defence traits and defence pathways induced upon aphid attack (Chen 2008). Breeders and growers are still struggling to find an efficient strategy for aphid control in major crop plants, but the KU Leuven iGEM project has a answer to this problem. Our project consists of a genetically engineered bacteria that can reduce the aphid damage on a sustainable way by hacking into their communication system.
Basic aphid biology
Aphids are an extremely successful group of insects which occurs throughout the world, with the greatest number of species in the temperate regions: Europe, North America and Asia (Dixon et al, 1987). As individuals they are small and inconspicuous. However, they can become so numerous that they can damage whole fields or orchards. The complex life cycles and polymorphism enable them to exploit their host plants and respond to every alteration of their environment to a high degree (Biology of Aphids, Dixon, 1973). Aphids are small, mostly soft-bodied insects of the super family Aphidoidea (World crop pests, 2A, Aphids their biology, natural enemies and control, minks and harrewijn). Their body can be green, black brown, pink or almost colourless (Biology of aphids, Dixon, 1973). About 4400 species of 10 families are known and around 10% of these species are serious pests for agriculture and forestry (Dedryver et al, 2010). Annual worldwide crop losses due to aphids are estimated at hundreds of millions of dollars (Morrison and Peairs 1998).
Figure 1ǀ Red, yellow-green and green pea aphids.
Figure 1ǀ Red, yellow-green and green pea aphids.
How aphids feed on plants
The head of aphids is pointed downward for feeding. They use modified mouth parts, stylets, to obtain their food by sucking plant juices (World crop pests, 2A, Aphids their biology, natural enemies and control, minks and harrewijn). Aphids passively feed on phloem sap of the plants. Once a phloem vessel, which is under high pressure, is punctured, the sap is forced into the aphid’s food canal. Phloem sap is rich in sugars, but poor in amino acids, which are essential for growth. Therefore, aphids ingest a very large amount of food in order to acquire sufficient proteins. The residual solution of digested food is ejected into the exterior in the form of a droplet of honeydew (Biology of Aphids, Dixon, 1973). This sugary liquid is produced through a ‘tail’ at the rear end of the aphid, called a cauda (World crop pests, 2A, Aphids their biology, natural enemies and control, minks and harrewijn). Most aphids also have paired tubular structures found at the end of the abdomen, called cornicles. Through these cornicles, aphids excrete droplets of a quick-hardening defensive fluid containing triacylglycerols, the cornicle wax. Other defensive compounds, like alarm pheromones, can also be secreted by the cornicles (aphid, McGraw-Hill Encyclopedia of Science and Technology).
Life cycles
Aphids display a diverse range of complicated life cycles (World crop pests, 2A, Aphids their biology, natural enemies and control, minks and harrewijn). Many aphid species are monophagous, they feed on only one plant species. The economically important aphids tend to have a wider host range and are polyphagous (Blackman and Eastop, 1985). They have a primary woody plant during winter and a secondary herbaceous plant in the summer (Dixon et al, 1994). In addition, aphid species have evolved a wide range of annual cycles and adaptive mechanisms that can vary between and within species (Biology of aphids, Dixon, 1973). Most aphids are parthenogenetic and viviparous for most of the year, but are also capable of sexual reproduction with the production of eggs during the summer. The annual cycle generally (97%) includes a single sexual generation. These mating females (oviparae) lay eggs, all of which are female. On hatching, each egg gives rise to a wingless offspring that gives birth parthenogenetically to further parhenogenetic females (viviparae). These may be winged or wingless, in response to environmental conditions (biology of aphids, Dixon, 1973). Crowding is a particularly strong stimulus to develop aphids of the winged, dispersal stage. Other external factors also play a role in the morph determination: food availability and quality, predators, photoperiod, time of the year and so on. In conclusion, aphids can rapidly exploit agricultural landscapes because of their high reproductive potential, dispersal capacities, adaptability to local environment, short generation time and feed on an endless source of plants (Dedryver et al, 2010).
Figure 3ǀSelection of host by aphid.
Figure 4ǀLife cycle of aphids.
Figure 1ǀ Red, yellow-green and green pea aphids.
Damage to plants and solutions
Aphid damage to plants may be caused directly, by nutrient drain, or indirectly by several mechanisms. These indirect mechanisms include plant virus transmission through the aphids’ piercing-sucking mouthparts, injection of saliva containing phytotoxic components that have a disastrous effect on plant growth and harmful fungi growth on the aphids’ honeydew hindering photosynthetic activity. Common damage symptoms on plants are decreased growth rates, mottled leaves, yellowing, stunted growth, curled leaves, gall formation and low yields and death (Biology of Aphids, Dixon, 1973). Different methods can be used to control an aphid infestation. For many crops, insecticides provide a simple and effective strategy for aphid control. However, the application of such chemicals is not desirable in the long term, because of the development of insecticide resistance and the potential negative effects on the population dynamics of other beneficial insects (World crop pests, 2A, Aphids their biology, natural enemies and control, minks and harrewijn). Aphids are vulnerable to many kinds of predators, including ladybird beetles and parasitoid wasps, and parasites and these can also be used to control aphids (World crop pests, 2A, Aphids their biology, natural enemies and control, minks and harrewijn).
