January 17, 2014
Largest Genome Ever Sequenced Belongs To Locust Species
April Flowers for redOrbit.com - Your Universe Online
The whole genome sequence of Locust (Locusta migratoria), the most widespread locust species, has been successfully decoded by researchers from the Institute of Zoology, Chinese Academy of Sciences, BGI and other institutes. The researchers were surprised by the remarkably large (6.5 gigabytes) yielded genome, which is the largest animal genome sequenced so far.Researchers have been surprised to find that a single locust is able to eat its own body-weight in food in a single day. Proportionately, this amount is 60 times a human's daily consumption. Locusts are capable of inflicting famine and wiping out livelihoods during swarms, which can cost countries billions of dollars in lost harvests and eradication efforts.
For the current study, published in Nature Communications, the research team used next generation sequencing technology to sequence L. migratoria. This technology yielded 721Gb of data, covering 114 x of the 6.3Gb locust genome size. The team was able to annotate and predict about 17,307 gene models and identify over 2,639 repeat gene families. The team also discovered that the top ten repeat families only represented 10 percent of the total genome sequences. This suggests that there were no dominant families in the L. migratoria genome.
The research team found that the reason why the locust has such a large genome compared to other reference insect genomes is a transportable element proliferation combined with slow rates of loss for these elements. Statistics reveal that repetitive elements constituted 60 percent of the assembled genome. The team also found that the genome exhibited the lowest rate of DNA deletions relative to the other insects.
The researchers performed comparative methylome and transcriptome analysis to investigate the potential involvement of epigenetic regulation in locust phase change. Interestingly, the researchers found that repetitive elements were highly methylated and introns had higher methylation levels than exons in the locust genome. They also found that there had been changes in genes involved in the regulation of the cytoskeletal microtubular system, as well as in neuronal activity during the onset of phase change in locusts from solitarious to swarm.
The most distinguishing feature of a locust is the long distance flight, which enables it to fly at speeds of up to hundreds of kilometers an hour; it is even able to cross the ocean. The current researchers found that the locust had developed a highly efficient energy supply system. This was accomplished by the expansion of genes in lipid metabolism and detoxification to fulfill the intensive energy consumption during its long-distance flight. The locust also displays an expansion of its gustatory and olfactory receptor gene families which are for its strong adaptation to host plant recognition.
In order to develop more effective insecticides, the research team identified the gene targets for pest control and new insecticides, such as cys-loop ligand-gated ion channels and G-protein-coupled receptors. These are considered to be major traditional insecticide targets, and the repertoire of several biological processes that could serve as mechanistic targets and lead to the development of specific and sustainable pest control methods.