A fragment carrying SCO1775-1773 including 240 bp upstream of SCO1775 (Figure  1H) led to partial restoration of the phenotype (data not shown). After complementation with cosmid I51, click here harboring a larger genomic region around SCO1774-1773, both deletion strains produced the grey spore pigment to the same level as M145 (Figure  8B). It is not clear why the shorter DNA fragments did not lead to full complementation

of the mutants. Possibly, even though there is a strongly predicted stem-loop structure immediately after SCO1773 that may serve a transcriptional terminator, polarity on the downstream gene SCO1772 may contribute to the mutant phenotype of the insertions/deletions in SCO1774-1773. Interestingly, L-alanine dehydrogenase has previously been implicated in development of both Bacillus subtilis and Myxococcus xanthus. Insertions in the ald gene in B. subtilis strongly reduced the efficiency of sporulation [34]. It was speculated that this may be due to a role of alanine dehydrogenase in deaminating the alanine derived from protein turnover and producing pyruvate that can be used for AP26113 chemical structure energy metabolism. This was supported by the partial suppression of the ald sporulation phenotype by enriching the medium with pyruvate. The up-regulation of ald transcription during

sporulation seemed not to be directly controlled by tested developmental regulators and may be affected

by substrate availability or other signals [34]. Mutation of aldA in M. xanthus negatively influenced development, causing delayed aggregation and reduced numbers and viability of spores [35]. The basis for this is unclear, and the required function of alanine dehydrogenase during development appeared not to be production of pyruvate. In similarity to M. xanthus aldA, the SCO1773 mutant phenotype was not affected by enrichment of the medium with pyruvate (data not shown). Nevertheless, the SCO1773 alanine dehydrogenase is required for maturation of spores in S. coelicolor and its expression during sporulation Phospholipase D1 is at least partially achieved by the whiA-dependent promoter P1774. The SCO1774 gene product shows an interesting similarity to the SARP-type transcription factor AfsR, but it lacks the SARP domain, which is the N-terminal 270 amino acids of AfsR that includes a winged helix motif and a bacterial transcriptional activation domain [33]. Thus, SCO1774 is not likely to encode a transcription factor, and the gene product shows similarity only to the C-terminal parts of AfsR with a tetratricopeptide repeat indicating involvement in protein-protein interactions, and an NB-ARC ATPase domain [36]. In summary, SCO1774 shows a clear-cut developmental transcriptional regulation that is dependent on whiA, but the biological function remains unclear.