Bongiorni, S., Mazzuoli, M., Masci, S., & Prantera, G. 2001 Facultative heterochromatization in parahaploid male mealybugs: involvement of a heterochromatin-associated protein.. Development 128(19): 3809-3817.

Notes: The behavior of chromosomes during development of the mealybug Planococcus citri provides one of the most dramatic examples of facultative heterochromatization. In male embryos, the entire haploid paternal chromosome set becomes heterochromatic at mid-cleavage. Male mealybugs are thus functionally haploid, owing to heterochromatization (parahaploidy). To understand the mechanisms underlying facultative heterochromatization in male mealybugs, we have investigated the possible involvement of an HP-1-like protein in this process. HP-1 is a conserved, nonhistone chromosomal protein with a proposed role in heterochromatinization in other species. It was first identified in Drosophila melanogaster as a protein enriched in the constitutive heterochromatin of polytene chromosome. Using a monoclonal antibody raised against the Drosophila HP-1 in immunoblot and immunocytological experiments, we provide evidence for the presence of an HP-1-like in Planococcus citri males and females. The results indicate a role for an HP-1-like protein in the facultative heterochromatization process.