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Systematics, Evolution, and Biodiversity

Member Symposium

Coverage of the Good and the Bad: The Genomes and Genomics of Pollinators and Pests

Chromosome-level genome of Bombus impatiens facilitates identification and comparative evolution of genes differentially expressed in heavy metal exposure

Tuesday, November 15, 2022

11:10 AM – 11:25 AM PT

Location: Vancouver Convention Centre, Meeting Room 119/120

Presenting Author(s)

KG

Katherine Geist

Iowa State University
Ames, Iowa

Co-author(s)

RM

Rick Masonbrink

Iowa State University
Ames, Iowa
Emeline Favreau (she/her/hers)

Bioinformatics Postdoc
University College London
London, England, United Kingdom
RF

Ryan Fortune

Iowa State University
Ames, Iowa
Mary Margaret Gardiner

Professor and Graduate Studies Chair
The Ohio State University
Columbus, Ohio
Sarah B. Scott

Graduate Student
The Ohio State University
Columbus, Ohio
SS

Seirian Sumner

University College London
London, England, United Kingdom
Sandra M. Rehan

Associate Professor of Biology
York University
Toronto, Ontario, Canada
Amy Toth

Associate Professor
Iowa State University
Ames, Iowa

Bumblebees are prolific pollinators even in urban settings, and one effect of urbanization on bumblebees is increased exposure to heavy metals. This has previously been shown to reduce colony size and overall fecundity in the native species Bombus impatiens, or eastern bumblebee. However, it is yet unclear what effects heavy metal exposure has on gene expression in bumble bees. Here, we present a hybrid (PacBio + Hi-C) chromosome-level assembly of 18 contiguous scaffolds (karyotype n = 18), which recovers over 97% of the existing Illumina genome. Further, in addition to gaining the contiguous chromosome-level assembly, our results suggest a gain in about 10% coverage in the new assembly, which may largely cover repeats missing from the previous assembly. Using annotations to this new assembly, we then identified differentially expressed genes in the brains and fat bodies of B. impatiens workers after exposure to heavy metals (arsenic, cadmium, chromium, lead). We used the improved chromosome-level assembly to test for lineage-specific rates of evolution in these genes and checked for collinearity of these genes in other bumblebee chromosome-level genome assemblies, using honeybee Apis mellifera as an outgroup. We discuss the impacts of urban heavy metal exposure on differential gene expression in B. impatiens, as well as evidence for possible selection pressures we have uncovered.