A cDNA macroarray approach to parasite-induced gene expression changes in a songbird host: genetic response of house finches to experimental infection by Mycoplasma gallisepticum



In 1994, the bacterial parasite
Mycoplasma gallisepticum
expanded its host range and
swept through populations of a novel host — eastern US populations of the house finch
Carpodacus mexicanus
). This epizootic caused a dramatic decline in finch population
numbers, has been shown to have caused strong selection on house finch morphology, and
presumably caused evolutionary change at the molecular level as finches evolved enhanced
resistance. As a first step toward identifying finch genes that respond to infection by
and which may have experienced natural selection by this parasite, we used
suppression subtractive hybridization (SSH) and cDNA macroarray approaches to identify
differentially expressed genes regulated by the
parasite. Two subtractive cDNA
libraries consisting of 16 512 clones were developed from spleen using an experimentally
uninfected bird as the ‘tester’ and an infected bird as ‘driver’, and vice versa. Two hundred
and twenty cDNA clones corresponding 34 genes with known vertebrate homologues and a
large number of novel transcripts were found to be qualitatively up- or down-regulated
genes by high-density filter hybridization. These gene expression changes were further
confirmed by a high throughout reverse Northern blot approach and in specific cases by
targeted Northern analysis.
searches show that heat shock protein (HSP) 90, MHC
II-associated invariant chain (CD74), T-cell immunoglobulin mucin 1 (TIM1), as well as
numerous novel expressed genes not found in the databases were up- or down-regulated
by the host in response to this parasite. Our results and macroarray resources provide a
foundation for molecular co-evolutionary studies of the
parasite and its
recently colonized avian host.

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Last updated on 05/24/2016