Zootermopsis nevadensis explained

Zootermopsis nevadensis, the Nevada termite, is a eusocial species of termite (Isoptera) in the family Archotermopsidae, a group known as the dampwood termites. It is a hemimetabolous organism.

Subspecies

Zootermopsis nevadensis is subdivided into two subspecies, Z. n. nevadensis and Z. n. nuttingi. It is the genome of Zootermopsis nevadensis nuttingi that has been sequenced.[1]

Range

The Nevada termite lives in central and central-east California, and in central-west Nevada.

Habitat

The Nevada termite lives in deserts, grasslands, prairies, and rural areas.

Predators

The Nevada termite is preyed on by passerine birds, shrews, spiders, lizards, salamanders, frogs, and toads.

Genome

The main objective of sequencing Zootermopsis nevadensis genome was to find molecular traces of eusociality. The authors compared the whole sequenced and assembled genome and 25 transcriptomes from different development states and castes with the already sequenced genomes of eusocial Hymenoptera and ants.

This termite only has two opsin genes copies, the smallest number of opsin genes known among the insects, as a result of living in the dark for tens of millions of years.

Male fertility

Among gene families with a significant expansion, four of them exhibit overexpression on fertile males and they are linked to male spermatogenesis or cellular division: Kelch-like proteins 10 (KLHL10) and Seven-in-abstenia (SINA). The codified proteins are associated with E3-ubiquitine-ligase complex implicated in espermatide proteins degradation. There are other gene families which are not expanded but shows a differential expression pattern among developmental stages and castes. Collectively, the data suggest an expanded role around spermatogenesis regulation and termite evolution.

Male termites complete gamete maturation after their moult. Male Z. nevadensis mate repeatedly during the mature stage and need to increase sperm production. Moreover, males activate and deactivate their testes cyclically.

Chemoperception

Zootermopsis nevadensis shows expansion on genes implied in chemical communication, a crucial component in insects societies. It has approximately 280 functional chemoreceptor genes. This number is over the average of insects, but intermediate among ants or bees.Although the total number of genes is comparable, its distribution within different gene families diverge from what has been observed in Hymenoptera.

The great difference between ORs and IRs gives an opportunity to study the organization of the olfactive lobe. The antennal lobe is formed by glomeruli. The glomeruli are tightly packed and they are composed by terminal axons projected from receptor neurons to the antennae. The sensor neurons which express the same chemoreceptors extend their axons to the same glomeruli. Z. nevadensis only has 72 glomeruli, the majority of them are joined to the 63 ORs. As a result, only a few number of IRs and GRs are implied in olfaction, the rest may be implied in gustation. The termite Z. nevadensis has a limited ability to discriminate odours.The majority of the termites live their lives within a single log. A colony rarely meet other termites outside the log. In the other hand eusocial insects like bees has a developed sense of smell. This feature provide bees a sophisticated weapon to identify their colony partners.

Immunity

Homogeneous populations living in high density are perfect targets for infections. This termite concretely lives in a pathogen-rich environment. The genome was analyzed in order to establish the relationship between eusociality and disease resistance. There were found all the vias related to immunity in Drosophila and other insects, including pattern recognition receptors, signaling pathways and regulatory genes.

Pathogens play an important role in eusocial insects, but the mechanisms improved to combat them differs in a taxon-specific manner.

Reproductive division of labor

The differentiation in castes and the reproductive division of labor is a marker of insect eusociality. Within Hymenoptera it has been proposed some regulators including vitelogenines (Vgs), juvenile hormone (JH), biogenic amines and other regulator like juvenile hormone binding proteins and some signaling pathways like insulin/insulin growth factor and yellow/major royal jelly protein like genes. The main genes involved in the reproductive division of labor are:

The reproductive division of labor is associated with an increased longevity of reproductives and histone-modifying enzymes take part in lifespan regulation. There was found two histone-deacetylases overexpressed in reproductive females, sirtuin 6 and sirtuin 7.

In eusocial insects and the reproductive division of labor is regulated by cuticular hydrocarbons. The reproductive status in Z. nevadensis is directed by the abundance of four long chain polyunsaturated alkenes. From 16 elongases and 10 desaturases found in Z. nevadensis one of each group is highly expressed in reproductive forms. The reproductive co-expression of these genes makes them hydrocarbon signaling regulators candidates in Z. nevadensis.[4]

Previous studies indicated that cytochromes P450 (CYP450) and hexamerins are implicated in caste differentiation.

Notes and References

  1. Molecular traces of alternative social organization in a termite genome . Nature Communications . 5 . 2014 . Terrapon . N. . Li . C. . Robertson . H. M. . Ji . L. . Meng . X. . Booth . W. . Chen . Z. . Childers . C. P. . Glastad . K. M. . Gokhale . K. . Gowin . J. . Gronenberg . W. . Hermansen . R. A. . Hu . H. . Hunt . B. G. . Huylmans . A. K. . Khalil . S. M. S. . Mitchell . R. D. . Munoz-Torres . M. C. . Mustard . J. A. . Pan . H. . Reese . J. T. . Scharf . M. E. . Sun . F. . Vogel . H. . Xiao . J. . Yang . W. . Yang . Z. . Yang . Z. . Zhou . J. . 29 . 24845553 . 3636 . 10.1038/ncomms4636 . 2014NatCo...5.3636T . free . 2286/R.I.44873 . free .
  2. Terrapon . Nicolas . Li . Cai . Robertson . Hugh M. . Ji . Lu . Meng . Xuehong . Booth . Warren . Chen . Zhensheng . Childers . Christopher P. . Glastad . Karl M. . Gokhale . Kaustubh . Gowin . Johannes . Gronenberg . Wulfila . Hermansen . Russell A. . Hu . Haofu . Hunt . Brendan G. . Huylmans . Ann Kathrin . Khalil . Sayed M. S. . Mitchell . Robert D. . Munoz-Torres . Monica C. . Mustard . Julie A. . Pan . Hailin . Reese . Justin T. . Scharf . Michael E. . Sun . Fengming . Vogel . Heiko . Xiao . Jin . Yang . Wei . Yang . Zhikai . Yang . Zuoquan . Zhou . Jiajian . Zhu . Jiwei . Brent . Colin S. . Elsik . Christine G. . Goodisman . Michael A. D. . Liberles . David A. . Roe . R. Michael . Vargo . Edward L. . Vilcinskas . Andreas . Wang . Jun . Bornberg-Bauer . Erich . Korb . Judith . Zhang . Guojie . Liebig . Jürgen . Molecular traces of alternative social organization in a termite genome . Nature Communications . 20 May 2014 . 5 . 1 . 3636 . 10.1038/ncomms4636. 24845553 . 2014NatCo...5.3636T . 2286/R.I.44873 . free .
  3. Masuoka . Yudai . Yaguchi . Hajime . Suzuki . Ryutaro . Maekawa . Kiyoto . Knockdown of the juvenile hormone receptor gene inhibits soldier-specific morphogenesis in the damp-wood termite Zootermopsis nevadensis (Isoptera: Archotermopsidae) . Insect Biochemistry and Molecular Biology . September 2015 . 64 . 25–31 . 10.1016/j.ibmb.2015.07.013. 26188329 . 2015IBMB...64...25M .
  4. Liebig . Jürgen . Eliyahu . Dorit . Brent . Colin S. . Cuticular hydrocarbon profiles indicate reproductive status in the termite Zootermopsis nevadensis . Behavioral Ecology and Sociobiology . October 2009 . 63 . 12 . 1799–1807 . 10.1007/s00265-009-0807-5. 6879252 .
  5. Cornette . R. . Koshikawa . S. . Hojo . M. . Matsumoto . T. . Miura . T. . Caste-specific cytochrome P450 in the damp-wood termite Hodotermopsis sjostedti (Isoptera, Termopsidae) . Insect Molecular Biology . April 2006 . 15 . 2 . 235–244 . 10.1111/j.1365-2583.2006.00632.x. 16640734 . 33172819 .