Indirect immune detection of ecdysone receptor (EcR) during the formation of DNA puffs in Bradysia hygida (Diptera, Sciaridae).

Gene amplification occurs in Bradysia hygida salivary glands, at the end of the fourth larval instar. The hormone 20-hydroxyecdysone (20E) triggers this process, which results in DNA puff formation. Amplified genes are activated in two distinct groups. The activity of the first group is dependent on high levels of 20E, while the second group needs low hormone levels. Consequently, the salivary glands of B. hygida constitute an interesting biological model to study how 20E, and its receptors, affect gene amplification and activity. We produced polyclonal antibodies against B. hygida EcR (BhEcR). In western blots a polypeptide of about 66 kDa was detected in salivary gland extracts. The antibodies were also used for indirect immune-localization of BhEcR in polytene chromosomes. RNA-polymerase II was also immune-detected. We did not detect the receptor in chromosome C where the first and second groups of DNA puffs form during DNA puff anlage formation, but it was present during puff expansion. During the active phase of both groups of DNA puffs, RNA polymerase II co-localized with BhEcR. After puff regression, these antigens were not detected. Apparently, EcR plays a direct role in the transcription of amplified genes, but its role in gene amplification remains enigmatic.

A proteome reference map for Vibrio cholerae El Tor.

A proteome reference map has been constructed for Vibrio cholerae El Tor, in the pI range of 4.0 to 7.0. The map is based on two-dimensional gels (2-D) and the identification, by peptide mass fingerprint, of proteins in 94 spots, corresponding to 80 abundant proteins. Two strains are compared, strain N16961 and a Latin American El Tor strain C3294. The consensus map contains 340 spots consistently seen with both strains grown in Luria-Bertani broth (LB) or minimal M9 medium. The results were obtained from nine gels run with 18 cm immobilized pH gradient strips and precast gels. The 2-D gels were anchored to real N16961 proteins identified by mass spectrometry. Various energy metabolism components and periplasmic ATP-binding cassette (ABC) transporter proteins were identified among the abundant proteins. Two isoforms of OmpU were found. Five operons are proposed and seven hypothetical proteins were experimentally confirmed. Comparisons are made with protein 2-D gels for a classical strain and to microarray analysis available for the N16961 El Tor strain. New results were obtained from the proteome analysis, indicating an abundance of periplasmic ABC transporter proteins not found in microarray studies.