Transcriptome profiling of sexual maturation and mating in the Mediterranean fruit fly, Ceratitis capitata

Abstract

Sexual maturation and mating in insects are generally accompanied by major physiological and behavioural changes. Many of these changes are related to the need to locate a mate and subsequently, in the case of females, to switch from mate searching to oviposition behaviour. The prodigious reproductive capacity of the Mediterranean fruit fly, Ceratitis capitata, is one of the factors that has led to its success as an invasive pest species. To identify the molecular changes related to maturation and mating status in male and female medfly, a microarray-based gene expression approach was used to compare the head transcriptomes of sexually immature, mature virgin, and mated individuals. Attention was focused on the changes in abundance of transcripts related to reproduction, behaviour, sensory perception of chemical stimulus, and immune system processes. Broad transcriptional changes were recorded during female maturation, while post-mating transcriptional changes in females were, by contrast, modest. In male medfly, transcriptional changes were consistent both during maturation and as a consequence of mating. Of particular note was the lack of the mating-induced immune responses that have been recorded for Drosophila melanogaster, that may be due to the different reproductive strategies of these species. This study, in addition to increasing our understanding of the molecular machinery behind maturation and mating in the medfly, has identified important gene targets that might be useful in the future management of this pest.

Figure 1. Changes in transcript abundances with maturation and mating in medfly heads.

The graphs include only GO annotated transcripts and show the number of enriched transcripts in the different samples belonging to different biological categories in A. mature virgin females compared to immature females, B. mature virgin males, compared to immature males, C. mated females compared to mature virgin females, and D. mated males compared to mature virgin males.

Figure 2. Differential transcript levels (Log₂ transformed fold changes) of six immune genes in sexually immature, mature virgin, and mated medfly, compared to mature virgin medfly transcript levels.

Transcript abundances were determined in immature (1V), mature virgin (4V) and mated (4M) female (upper) and male (lower) medfly heads and abdomens. Transcript abundances are expressed as ratios are compared to mature virgin levels (4V). Broken lines indicate that transcript abundances were very low. Stars indicate significant difference in transcript abundances (*P<0.05, **P<0.01, ***P<0.001, two-tailed t-test on three replicates) in the pairwise comparison between immature and mature virgin flies, or mature virgin and mated flies. Lines between data points are purely for ease of graphical interpretation and do not imply a continuous relationship between data points.