|Rider jr., S. dean|
Submitted to: Molecular Genetics and Genomics
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/16/2011
Publication Date: 5/15/2011
Citation: Kroemer, J.A., Coates, B.S., Nusawardani, T., Rider Jr., S., Fraser, L.M., Hellmich II, R.L. 2011. A rearrangement of the Z chromosome topology influences the sex-linked gene display in the European corn borer, Ostrinia nubilalis. Molecular Genetics and Genomics. 286(1):37-56. Interpretive Summary: Genes located on the Z sex chromosome in Lepidoptera (butterflies and moths) play important roles in establishing the numbers of insects produced per season (voltinism) as well as the ability of opposite sexes to locate mates in the field (male pheromone responses). These traits can be extremely important for pest species such as the European corn borer whose inherent ability to find mates, abundance, and generation times in the field directly impacts whether established economic injury levels are reached. Transgenic crops incorporating insecticidal Bacillus thuringiensis (Bt) toxins have become an effective and integrated means of suppressing corn borer populations in recent years, but there is ongoing concern that resistance to the toxin may develop in the pest through behavioral or physiological means. This study provides an enhanced resolution of the Z chromosome architecture in the European corn borer, incorporating and comparing a genetic map, gene expression data, and sequence data gathered for a panel of 50 sex-linked genes identified in the silkworm genome. Together, these data provide new and valuable insights into Lepidopteran genetic structures that can be used to identify and evaluate important genes responsible for influencing the field status of pest populations. The type and degree of change in a pest’s phenotype can directly influence its potential for developing both physiological and behavioral resistance against modern control tactics such as genetically-engineered crops. Understanding where and when these genetic changes occur in pest populations enhances our ability to trace and predict their agricultural impacts, and to establish new effective control strategies if and when a realized threat exists. This information will be useful to scientists interested in basic lepidopteran genetics and evolution, and scientists interested in controlling lepidopteran pests.
Technical Abstract: The sex determination system of Lepidoptera is comprised of heterogametic females (ZW) and homogametic males (ZZ), where voltinism (Volt) and the male pheromone response traits (Resp) are controlled by genes housed on the Z-chromosome. Volt and Resp determine traits that lead to ecotype differentiation in Ostrinia nubilalis and influence gene flow within and among populations. Degenerate primer pairs were designed to Polymerase Chain Reaction (PCR) amplify 50 Bombyx mori Z chromosome-linked genes in Lepidoptera. Thirty-five orthologs were amplified in O. nubilalis of which 10 were polymorphic and integrated into a linkage and partial bacterial artificial chromosome (BAC) physical map. Predicted arrangement of Z-linked genes in O. nubilalis shows a high degree of co-linearity with B. mori chromosome 1 (Z), although detection of a translocation disrupted synteny at one chromosome end. The expression of O. nubilalis Z chromosome-linked genes shows conservation of tissue and growth-stage specific expression when compared with B. mori orthologs. Resolution of the O. nubilalis Z chromosome will provide tools for Quantitative Trait Loci (QTL) mapping of sex-linked traits and implicate genome rearrangements as a possible mechanism for differential gene regulation in Lepidoptera.