Location: Stored Product Insect and Engineering Research
Project Number: 3020-43000-034-016-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 1, 2021
End Date: Aug 31, 2026
Objective:
Many species of stored product insects feed on similar foods, and thus, may use the same volatile cues to locate suitable food sources as they navigate throughout the landscape. However, little information is known about the molecular mechanisms that most stored product insects use to recognize and respond to food odors and locate food sources or whether similar mechanisms are used by multiple species to respond to the same olfactory cues. Additionallly, while several genes for coding for chemosensory proteins have been annotated and functionally characterized in red flour beetle (Tribolium castaneum), genes coding for olfactory receptors, odorant binding proteins, and other sensory genes have not been curated or functionally characterized in most other stored product insect species.
High-quality chromosome-scale genome assemblies were recently produced for ~20 different stored product insects species, including members of the families Tenebrionidae, Ptinidae, Dermestidae, Bostrichidae, and Pyralidae, which can be used as a foundation for expanding chemosensory genomic resources for stored product insects. Furthermore, identifying food volatiles that are attractive to multiple species of stored product insects and determining whether insects within the same taxonomic family harbor orthologous genes capable responsible for responding to the same volatile cues can provide a foundational basis for investigating the function of chemosensory genes in stored product insects. Thus, the objectives of this agreements are to: 1) generate annotations of chemosensory genes for two closely related members of the family Bostrichidae (lesser and larger grain borer (Rhyzopertha dominica and Prostephanus truncatus)), 2) determine whether these insects respond to similar food and/or microbial volatiles and other semiochemicals, 3) determine which compounds in these volatile blends elicit antennal and/or responses, 4) determine if orthologous genes are differentially expressed in olfactory tissues in these two closely related species in response to the same volatile cues, 5) assess whether stored product insects in other taxonomic families (Ptinidae or Curculionidae) also exhibit antennal and behavioral responses to volatiles identified in items 2-3 and determine whether these insects have homologous chemosensory genes that enable the detection of these compounds.
Approach:
We will use a combination of wind tunnel behavioral assays to determine whether the two Bostrichids are attracted to the same food and microbial volatile cues, GC-EAD to determine whether Bostrichids elicit antennal responses to the same compounds in the volatile blends, and GC-MS to identify compounds that elicit consistent anteannal responses. In addition, chemosensory genes of Bostrichids will be manually curated using a combination of tblastn searches of annotated chemosensory genes from other model Coleopteran insects and antennal RNA-Seq data. Orthology will be predicted using a combination of Orthofinder and synteny analysis to determine whether chemosensory genes are located in regions that exhibit collinearity between the two Bostrichids. Gene expression analysis will be performed using RNA-Seq to determine whether orthologous genes are induced in response to the same food or microbial volatile blends. Similar experiments will be performed to determine whether similar behavioral, antenanal, and gene expression responses also occur in Ptinids and Curculionids. A combination of RNA-Seq and standard toxicological assays, microbiological methods, and bioassays will be used to investigate molecular interactions between insects and mycotoxin producing fungi.
