Differential gene expression during wing morph differentiation of the ectoparasitoid Melittobia digitata (Hym., Eulophidae).

Melittobia digitata is an ectoparasitoid of solitary bees and wasps that displays a trade-off between reproduction and dispersion through the development of two wing morphs (long and short wing morphs (LWM and SWM)). The morph differentiation of this species is an exceptional adaptation to maximize host exploitation and habitat colonization, and an understanding of the mechanisms underlying this developmental process will shed light on how nutrients or environmental elicitors alter regulatory pathways leading to physiological and metabolic changes resulting in such drastic developmental rearrangements. Here we describe the differential gene expression between SWM and LWM larvae of M. digitata in order to unravel the molecular mechanisms controlling the morph differentiation in this minute parasitoid and pinpoint the pathways involved in the regulation of this developmental process. The suppression subtractive hybridization (SSH) methodology was used to isolate differentially expressed genes using mRNA populations collected soon after morph development commitment. Dot blot analysis of 384 clones from a forward SSH library identified approximately 200 differentially expressed clones, including those transcripts present in very low abundance. Further DNA sequence analysis of a sub-population of 42 clones revealed 31 putatively unique transcripts, from which 5 were further analyzed by Northern blot analysis and semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR). The complete cDNA of one of these transcripts, a putative metalloprotease, was fully sequenced and is described. The role of the putative differentially expressed genes during the wing morph differentiation of M. digitata is discussed.