These results indicated that the bldKB-g disruption never affects A-factor production or secondary metabolism. RT-PCR analysis confirmed ABT-888 mouse that bldKB-g, bldKC-g, bldKA-g, bldKD-g, and bldKE-g were cotranscribed (Fig. S3). Therefore, we cloned the entire bldK-g gene cluster, together with 885 and 158 bp sequences upstream of SGR2418 and downstream of SGR2414, respectively, into pTYM19 (Onaka et al., 2003), and thereby generated pTYMbldK-g. When pTYMbldK-g was integrated into the chromosome of the ΔbldKB-g strain, aerial mycelium formation and bialaphos sensitivity were restored

(Fig. 1b and c). We then constructed pTYMbldK-c containing the promoter region of bldK-g and the entire bldK-c cluster. When pTYMbldK-c was integrated into the chromosome of the ΔbldKB-g strain, aerial mycelium formation and bialaphos sensitivity were also restored (Fig. 1b and c). Based on these findings, we concluded that the bldK-g operon encoded an oligopeptide ABC transporter involved in aerial mycelium formation that was functionally equivalent to the bldK-c operon in S. coelicolor A3(2). Baf-A1 in vitro Gram-positive bacterium B. subtilis uses

a signaling oligopeptide, competence and sporulation-stimulating factor (CSF). CSF is generated from its precursor protein by processing proteases (Lanigan-Gerdes et al., 2007). CSF is imported into the cell by an oligopeptide ABC transporter, Opp (formally Spo0K) (Solomon et al., 1995, 1996), and stimulates competence and sporulation by antagonizing RapC and RapB activities, respectively (Perego, 1997; Core & Perego, 2003). Although the signaling peptide(s) in Streptomyces has not yet been revealed, the BldK transporter probably has a function similar to that of B. subtilis Opp. Identification of the signaling peptide and elucidating its molecular function

are required for the understanding of the BldK-dependent regulation of morphological development in Streptomyces. Previously, we proposed that AdpA directly controls the transcription of the bldK-g operon, because bldKB-g transcripts were barely detectable many in the ΔadpA mutant strain grown in SMM liquid for 24 h, and because AdpA bound sequences upstream of the bldKB-g promoter in vitro (Akanuma et al., 2009). Therefore, putative direct control of bldKB-g by AdpA was further examined. First, the time course of bldKB-g transcript induction was analyzed in the WT and ΔadpA strains by S1 nuclease mapping. In SMM liquid, the transcription of bldKB-g was significantly reduced in the ΔadpA strain compared with the WT strain (Fig. 2a), which corroborated our previous findings (Akanuma et al., 2009). However, on YMPD agar, considerable amounts of the bldKB-g transcript were detected even in the ΔadpA strain (Fig. 2b).