World's largest animal genome belongs to locust: New insight explains swarming, long-distance migratory behaviors

One surprise from the study is that a single locust can eat its own bodyweight in food in a single day; this is, proportionately, 60 times a human's daily consumption. They are capable of inflicting famine and wiping out livelihoods when they swarms, which can cost countries billions of dollars in lost harvests and eradication efforts.

In this study, researchers sequenced Locusta migratoria using next-gen sequencing technology, totally yielding 721Gb of data, which covered 114 × of the 6.3Gb locust genome size. They annotated and predicted about 17,307 gene models, and identified over 2,639 repeat gene families. Moreover, they discovered that the top ten repeat families only represented 10% of the total genome sequences, suggesting that there were no dominant families in the L. migratoria genome.

Compared with other reference insect genomes, researchers found the reason why locust has such large genome is transposable element proliferation combined with slow rates of loss for these elements. According to statistics, repetitive elements constituted 60% of the assembled genome. The transposable element in the Locust genome was expanded when comparing with the other insects. Besides, they also found that the locust genome exhibited the lowest rate of DNA deletions relative to the other insects.

To investigate the potential involvement of epigenetic regulation in locust phase change, researchers performed comparative methylome and transcriptome analysis. One interesting finding was that repetitive elements were highly methylated and introns had higher methylation levels than exons in locust genome. It was also noteworthy that there had changes in genes involved in the regulation of the cytoskeletal microtubular system and in neuronal activity during the onset of phase change in locusts from solitarious to swarm.

As we all know, locust has an most distinguishing feature- the long-distance flight- which enables them can fly at speed of hundreds of kilometers an hour, or even cross the ocean. In this study, researchers found that locust had developed a highly efficient energy supply system by expansion genes in lipid metabolism and detoxification to fulfill the intensive energy consumption during their long-distance flight. The expansion of its gustatory and olfactory receptor gene families is for its strong adaptation to host plant recognition.

To advance the development of new effective insecticides, researchers identified the gene targets for pest control and new insecticides, such as cys-loop ligand-gated ion channels and G-protein-coupled receptors, which are considered to be major traditional insecticide targets, and the repertoire of several biological processes that may serve as mechanistic targets and lead to the development of specific and sustainable pest control methods.