title: Expression analysis of the spi gene in the pock-forming plasmid pSA1.1 from Streptomyces azureus and localization of its product during differentiation.
abstract: The sporulation inhibitory gene spi in the pock-forming conjugative plasmid pSA1.1 of Streptomyces azureus was introduced into cells via a high or low copy number vector to examine the effect of gene dosage on the growth of Streptomyces lividans TK24 as a host. In transformants carrying a high spi copy number, nutrient mycelial growth was inhibited, as was morphological differentiation from substrate mycelium to aerial mycelium on solid media. The degree of inhibition depended on the spi gene dosage, but the presence of pSA1.1 imp genes, which encode negative repressor proteins for spi, relieved the inhibition. Confocal images of Spi tagged with enhanced green fluorescent protein in cells on solid media revealed that spi expression was initiated at the time of elongation of substrate mycelium, that its expression increased dramatically at septation in aerial hyphae, and that the expression was maximal during prespore formation. Expression of spi covered the whole of the hyphae, and the level of expression at the tip of the hyphae during prespore formation was about sixfold greater than during substrate mycelial growth and threefold greater than during aerial mycelial growth. Thus, localized expression of spi at particular times may inhibit sporulation until triggering imp expression to repress its inhibitory effects.
authors.affiliation: Microbial Division, Institute of Genetic Resources, Faculty of Agriculture, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan. doi@agr.kyushu-u.ac.jp
authors.forename: Katusmi
authors.initials: K
authors.lastname: Doi
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Ohyama
authors.forename: Eiji
authors.initials: E
authors.lastname: Yokoyama
authors.forename: Takashi
authors.initials: T
authors.lastname: Nishiyama
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Fujino
authors.forename: Yuko
authors.initials: Y
authors.lastname: Nagayoshi
authors.forename: Toshihisa
authors.initials: T
authors.lastname: Ohshima
authors.forename: Seiya
authors.initials: S
authors.lastname: Ogata
mesh_terms: D001426:Bacterial Proteins / Q000032:analysis* / Q000235:genetics; D003600:Cytosol / Q000737:chemistry; D018628:Gene Dosage; D020869:Gene Expression Profiling; D018613:Microscopy, Confocal; D010957:Plasmids; D013302:Streptomyces / Q000737:chemistry* / Q000166:cytology / Q000235:genetics / Q000254:growth & development*
chemical_list: D001426:Bacterial Proteins