Termite Genome Sheds Light On Social Behavior

The first termite genome fills the gap in our understanding of social insect genomics.

AsianScientist (May 28, 2014) – In a study published in Nature Communications, researchers from China, America and Germany have sequenced and analyzed the first termite genome (Zootermopsis nevadensis), providing insights into the molecular underpinning of complex societies in termites.

Like ants and honey bees, termites are eusocial insects. In colonies of termites, only a few individuals have reproductive ability (called queens and kings), while other individuals perform non-reproduction tasks like foraging, brood care or defense. Living in societies has helped termites adapt to their environments and contributed to their ecological success.

Although similar in some aspects to ants and honey bees, which belong to order Hymenoptera, termites evolved eusociality in a distantly related order called Isoptera. Termites also exhibit different pattens regarding sociality compared to social Hymenopterans. For instance, termite kings, which are long-term male reproductives and have the same status as the queens, are absent in social Hymenopterans. So far, ten social Hymenopteran genomes (eight ants and two bees) have been published, but no termite genome has been published up to now.

Z. nevadensis has the smallest genome size known among termites (only about 500Mb), which was beneficial for building the assembly with short sequencing reads. In addition to the genomic data, the researchers also generated transcriptomic data for 25 samples, representing different sexes, developmental stages and castes.

“One of the major findings in our study is that four gene families involved in spermatogenesis have expanded in the termite genome. From the transcriptome data, we also observed up-regulated expression of these genes in male reproductive individuals” said Dr. Li Cai, co-author of the study.

“This is very interesting, because in a termite colony queens and kings mate repeatedly during their long lives, while in the eusocial Hymenopterans, the reproduction system is usually queen-centralized and single-time mating. Our findings shed light on the molecular explanations for such difference, though further work is needed for a full understanding.”

By comparing with other eusocial insect genomes, the researchers also found some gene families (e.g. vitellogenins, cytochrome P450s and hexamerins) involved in caste differentiation and reproductive division of labour in social Hymenopteran insects show similar patterns in termites, suggesting the convergent evolution of these regulatory mechanisms.

“This first termite genome represents an important step, because it fills a big gap in social insect genomics. Scientists have long wondered if there is any common mechanism leading to the development of eusociality in different eusocial insect groups,” said co-corresponding author of the study Dr. Zhang Guojie from China National Genebank.

“We found several regulatory factors like vitellogenins and juvenile hormone that displayed significantly gene expression changes among castes of termite, similar to other eusocial insects. With more and more social insect genomes available, we can have a closer look at this question with comparative genomic analyses among different social insect groups and will hopefully get a more thorough understanding of social evolution”

The article can be found at: Terrapon et al. (2014) Molecular Traces of Alternative Social Organization in a Termite Genome.


Source: BGI; Photo: Matt Johnson/Flickr/CC.

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