Expression profiles of an inactive aspartic protease (Bla g 2 allergen) in different tissues and developmental stages of the German cockroach (Blattella germanica)

Tergal glands are found in many insect species and contain constituents such as pheromones, sugars, proteins, and so forth. Preliminary studies have revealed that tergal gland secretions in the German cockroach (Blattella germanica L.) contain the human allergen Bla g 2 (B. germanica allergen 2), an inactive aspartic protease. Although Bla g 2 protein expression has been detected previously in various German cockroach body parts, including male tergal glands, studies that link protein expression in various life stages and tissues with mRNA and protein abundance have not been conducted. Therefore, the goal of this study was to measure the relative abundances of Bla g 2 protein and mRNA in different tissues and life stages of B. germanica using immunoblotting, quantitative PCR, and liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based quantitative profiling. We found that Bla g 2 protein was detected in every sampled tissue, including the male tergal glands. Protein abundance was relatively high in adult males and their tergal glands in comparison to nymphs and virgin females. Similarly, Bla g 2 mRNA transcript levels were also comparatively higher in male tergal glands and adult males. In conclusion, this study provides new information on the relative abundance and distribution of Bla g 2 allergen, a medically significant protein, in different tissues and developmental stages of the German cockroach and lays the foundation for future studies that aim to determine the function of this protein in B. germanica development.