Figure 9.

Simplified representation of the developmental regulatory network, highlighting the involvement of BldO and the importance of whiB as a node (adapted from Nat Rev Microbiol 2015, 13, 749–760, with permission).

Both BldM (Al‐Bassam et al., 2014) and σ^BldN (of which RsbN is the cognate anti‐sigma factor; Bibb et al., 2012) are required for the formation of aerial hyphae. During vegetative growth, whiB expression is repressed both by BldD‐(c‐di‐GMP) and by BldO. Relief from repression by BldD (presumably due to a drop in c‐di‐GMP levels) and BldO (by an unknown mechanism) and activation by BldM leads to expression of whiB. Once produced, WhiB combines with WhiA to initiate developmental cell division.