Résumé
The acquisition of tissue samples from wild populations is a constant
challenge in conservation biology, especially for endangered species and
protected species where nonlethal sampling is the only option. Whole blood
has been suggested as a nonlethal sample type that contains a high
percentage of bodywide and genomewide transcripts and therefore can be
used to assess the transcriptional status of an individual, and to infer a
high percentage of the genome. However, only limited quantities of blood
can be nonlethally sampled from small species and it is not known if
enough genetic material is contained in only a few drops of blood, which
represents the upper limit of sample collection for some small species. In
this study, we developed a nonlethal sampling method, the laboratory
protocols and a bioinformatic pipeline to sequence and assemble the whole
blood transcriptome, using Illumina RNA-Seq, from wild greater mouse-eared
bats (Myotis myotis). For optimal results, both ribosomal and globin RNAs
must be removed before library construction. Treatment of DNase is
recommended but not required enabling the use of smaller amounts of
starting RNA. A large proportion of protein-coding genes (61%) in the
genome were expressed in the blood transcriptome, comparable to brain
(65%), kidney (63%) and liver (58%) transcriptomes, and up to 99% of the
mitogenome (excluding D-loop) was recovered in the RNA-Seq data. In
conclusion, this nonlethal blood sampling method provides an opportunity
for a genomewide transcriptomic study of small, endangered or critically
protected species, without sacrificing any individuals.