Transcriptional analyses of pk1 and pk2 alleles. (A) Transcriptional results of the pk1 and pk2 alleles obtained from gonads of eight isopod species harbouring either feminizing (F) or CI-inducing (CI) Wolbachia strains. Plus or minus signals indicate expression, or not, of the copy(ies). Distinction is made between the two different pk2 alleles named pk2 b1 and pk2 b2 within the pk2b type. F: female; M: male. NA: no pk2a type alleles were amplified in these strains. (B) Transcriptional results of pk2b1 and pk2b2 alleles are shown from ovaries or testes (when infected) of eight isopod species. Primers used are shown in ( Additional file 1: Table S1). The DNA template control (only w VulC presented) shows the intensity and specificity of the band detected with each pair of primers. RT + and RT- indicate, respectively, the presence or the absence of reverse transcriptase in the reactions. M: DNA size markers. (C) Transcriptional results of the 16S rDNA, pk2b2 and orf7 genes in seven different tissues of A. vulgare harbouring the w VulC Wolbachia strain. Ov: ovaries; Hae: haemocytes; HO: hematopoietic organ; Br: brain; N ch: nerve chain; gut; Ad: adipose tissue.