Differential expression of β-tubulin isotypes in different life stages of Parascaris spp after exposure to thiabendazole

[Display omitted] •β-tubulin isotype 1 and 2 was differentially expressed at selected life stages.•Isotype 1 was expressed at all life stages.•Isotype 2 expression was strong in eggs and very weak in L2/3 and adult worms.•Each isotype has specific functions during embryogenesis.•Exposure to TBZ for five days altered β-tubulin gene expression of isotype 1. Anthelmintic resistance (AR) to macrocyclic lactones (ML) has been described in Parascaris of horses world-wide. In contrast, benzimidazoles (BZ) are still effective, although reduced efficacy to this drug class was recently reported. The mode of action of BZ is binding to β-tubulin, which prevents polymerisation of microtubules. In this study, β-tubulin gene expression of isotypes 1 and 2 was investigated at seven time points (0, 6, 24, 72, 96 and 120h) during embryogenesis and in adult worms. In addition, an in ovo larval developmental test was developed to study β-tubulin gene expression of both isotypes in parasacaris eggs after exposure to different concentrations of thiabendazole (TBZ) for five days at 25°C. A strong pattern of differential expression of β-tubulin and isotype 1 was observed in all stages, while isotype 2 expression was mainly found at an early phase of the embryogenesis. For isotype 1, a 5-fold increase was observed during the first 48h, but gene expression gradually decreased after 72, 96 and 120h. Isotype 2 was only expressed during the first 24h, followed by a 130-fold decrease at (time points) 72, 96 and 120h. The in ovo larval developmental test, in which we exposed initially unembryonated eggs to increased concentrations of TBZ, did affect isotype 1 gene expression but not isotype 2. This assumes that each isotype has specific functions in different life stages. This is in agreement with the ‘multi-tubulin’ hypothesis, which states that different tubulin isotypes are required for specialised microtubule functions. Isotype 1 is the most likely drug target for BZs, as isotype 2 was only expressed at very low levels later in development. Increasing concentrations of TBZ altered β-tubulin isotype 1 gene expression after exposure of the eggs for five days, but this was not seen for isotype 2.