B-chromosome effects on Hsp70 gene expression does not occur at transcriptional level in the grasshopper Eyprepocnemis plorans

Abstract

As intragenomic parasites, B chromosomes can elicit stress in the host genome, thus inducing a response for host adaptation to this kind of continuous parasitism. In the grasshopper Eyprepocnemis plorans, B-chromosome presence has been previously associated with a decrease in the amount of the heat-shock protein 70 (HSP70). To investigate whether this effect is already apparent at transcriptional level, we analyze the expression levels of the Hsp70 gene in gonads and somatic tissues of males and females with and without B chromosomes from two populations, where the predominant B chromosome variants (B2 and B24) exhibit different levels of parasitism, by means of quantitative real-time PCR (qPCR) on complementary DNA (cDNA). The results revealed the absence of significant differences for Hsp70 transcripts associated with B-chromosome presence in virtually all samples. This indicates that the decrease in HSP70 protein levels, formerly reported in this species, may not be a consequence of transcriptional down-regulation of Hsp70 genes, but the result of post-transcriptional regulation. These results will help to design future studies oriented to identifying factors modulating Hsp70 expression, and will also contribute to uncover the biological role of B chromosomes in eukaryotic genomes.

Transcription of a B chromosome CAP-G pseudogene does not influence normal Condensin Complex genes in a grasshopper

“…According to the results of validation and stability analysis of reference genes in E. plorans described in Navarro-Domínguez et al . 70 , two or three reference genes were employed here, specifically Act-RP49 for somatic tissue and ovaries from Salobreña females, GAPDH-Tub for somatic tissue and Act-Tub-Arm for testes from Salobreña males, RP49-Act-Arm for somatic tissue and Act-Arm for ovaries from Torrox females, and Act-Tub for somatic tissue and Act-RP49 for testes from Torrox males.…”

“…Relative Quantities (RQs) were calculated referred to a calibrator sample, following the same method described in Navarro-Domínguez et al . 70 . In cDNA reactions, RQ values were normalized by the geometrical average of the most stable reference genes for each sample type 71 .…”