Abstract
Parasitism by endoparasitoid wasps changes the expression of various host genes, and alters host immune and developmental processes. However, it is not clearly understood how parasitism changes host gene expression in a whole genome scale. This study focused on an epigenetic control of Cotesia plutellae, an endoparasitoid wasp, against its host, Plutella xylostella. Two DNA methyltransferases (DNMT-1 and DNMT-2) are encoded in the genome of P. xylostella. In addition, methyl-binding domain proteins (MBDs) and DNA demethylation factor, ten-eleven translation protein (TET) are encoded. DNA methylation of P. xylostella genomic DNA was confirmed by restriction digestion with Gla I specific to 5-methylcytosine. DNA methylation intensity in parasitized (P) larvae was decreased compared to that in nonparasitized (NP) larvae, especially at late parasitic stage, at which expression levels of both DNMT-1 and DNMT-2 were also decreased. DNA demethylation of P. xylostella was confirmed in both NP and P larvae by restriction digestion with PvuRts1I recognizing 5-hydroxymethyl cytosine. Parasitism also suppressed expression levels of TET and MBDs. Treatment of 5-aza-2′-deoxycytidine (AZA) reduced DNA methylation intensity of NP larvae, causing suppression of hemocyte-spreading behavior and delay of immature development. RNA interference of DNMT-1 or DNMT-2 mimicked the adverse effects of AZA.
Highlights
Analysis has indicated that more than 25% of host genes annotated into various categories of physiological functions are altered in gene expression after being parasitized[3]
The DNA methylation amounts of P. xylostella larvae were compared among different insect species
DNA methylation is a way to transmit epigenetic information to the generation. It is a covalent modification of DNA by adding methyl group mostly to cytosine at CpG sequence in animals with catalytic activities of DNMTs
Summary
Analysis has indicated that more than 25% of host genes annotated into various categories of physiological functions are altered in gene expression after being parasitized[3]. We hypothesized that C. plutellae parasitism could alter host gene expression in an epigenetic mode by changing DNA methylation level in addition to manipulating the activities of host transcriptional factors. To test this hypothesis, DNA methylation was monitored in P. xylostella and the DNA methylation levels in parasitized (P) larvae were compared to those in nonparasitized (NP) larvae. This study demonstrated the effect of down-regulation of DNA methylation on immune response and immature development of P. xylostella
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