WhiA, a Protein of Unknown Function Conserved among Gram-Positive Bacteria, Is Essential for Sporulation in Streptomyces coelicolor A3(2)

Abstract

The whiA sporulation gene of Streptomyces coelicolor A3(2), which plays a key role in switching aerial hyphae away from continued extension growth and toward sporulation septation, was cloned by complementation of whiA mutants. DNA sequencing of the wild-type allele and five whiA mutations verified that whiA is a gene encoding a protein with homologues in all gram-positive bacteria whose genome sequence is known, whether of high or low G؉C content. No function has been attributed to any of these WhiA-like proteins. In most cases, as in S. coelicolor, the whiA-like gene is downstream of other conserved genes in an operon-like cluster. Phenotypic analysis of a constructed disruption mutant confirmed that whiA is essential for sporulation. whiA is transcribed from at least two promoters, the most downstream of which is located within the preceding gene and is strongly up-regulated when colonies are undergoing sporulation. The up-regulation depends on a functional whiA gene, suggesting positive autoregulation, although it is not known whether this is direct or indirect. Unlike the promoters of some other sporulation-regulatory genes, the whiA promoter does not depend on the sporulation-specific factor encoded by whiG.Dispersal of the mycelial organism Streptomyces coelicolor A3(2) occurs by the formation of long chains of spores from aerial hyphae. A critical stage in this process is the subdivision of a multigenomic apical aerial hyphal compartment into many unigenomic prespore compartments by the synchronous formation of regularly spaced sporulation septa (26,38). At least six genetic loci (whiA, whiB, whiG, whiH, whiI, and whiJ) are needed for sporulation septation (8, 10), in addition to cell division genes that are also involved in vegetative growth (24,25). These six early whi loci appear to play no role in vegetative growth. Mutations in them have pleiotropic effects on the later stages of sporulation, including weak or undetectable transcription of the genes responsible for the production of grey spore pigment (20), hence the white colony phenotype after which they were named (18). Transcription of sigF, which encodes a late sporulation sigma factor, is also dependent on these early whi genes (21, 28). The complex early whi mutant phenotypes suggest that some or all of the six "early" whi genes encode regulatory elements. Indeed, whiG encodes a sigma factor ( WhiG [11,37]), whiH encodes a repressor-like protein (31), and whiI encodes a response regulator-like protein (1); the product of whiB has features that resemble those of some transcription factors (13,34). Mutations in some other more recently discovered genes also affect sporulation septation but in a more allele-specific manner (30).This paper is concerned with whiA. Like whiB mutants, whiA and whiA whiB double mutants have tightly coiled aerial hyphae that are markedly longer than normal spore chains, contain uncondensed DNA, and lack sporulation septa and readily detectable FtsZ (9, 15, 33). whiA and whiB are therefore believed to play a role in th...

The Conserved DNA-Binding Protein WhiA Is Involved in Cell Division in Bacillus subtilis

“…YvcL is a DNA-binding protein and shows strong homology with the protein WhiA from Streptomyces coelicolor. WhiA regulates the expression of several genes during sporulation, including ftsZ (26,27). Surprisingly, transcriptome analyses of a yvcL mutant did not show a transcriptional effect on known cell division genes in B. subtilis, and the localization of YvcL binding sites on the genome gave no clear indication that YvcL functions as a transcription factor.…”

Developmental Control of aparABPromoter Leads to Formation of Sporulation-Associated ParB Complexes inStreptomyces coelicolor

“…Both whiA and whiB have two promoters, one low-level constitutive and another strongly transcribed at the time of aerial mycelium growth (2,49). whiA and whiB deletion mutants have abnormally long coiled aerial hyphae, implying that they are defective in signals for growth cessation (15).…”

“…Several whi genes (including whiA, whiB, whiH, whiI, and whiG) are regulators of the early stages of sporulation (1,2,8,11,13,15,44). Mutants of these five genes are defective in sporulation septation (15).…”

“…Mutants of these five genes are defective in sporulation septation (15). whiA encodes a protein of unknown function with orthologues in most other grampositive bacteria (2). whiB belongs to group of genes found only in actinomycetes, encoding small putative transcription factors containing an Fe-S cluster (13,25).…”

The Product of a Developmental Gene, crgA , That Coordinates Reproductive Growth in Streptomyces Belongs to a Novel Family of Small Actinomycete-Specific Proteins

“…Most of these whi genes appear to encode regulatory functions. Among the early whi genes, whiG encodes an alternative sigma factor (29); whiA encodes a protein of unknown function (2); whiB encodes a small, highly charged, and cysteine-rich protein of unknown function (20); whiH encodes a member of the GntR family of transcription factors (24); and whiI encodes a protein resembling the response regulator of a two-component sensor-regulator system, although there is no adjacent recognizable kinase gene and WhiI itself lacks important amino acid residues normally needed for phosphorylation to take place (1). On the basis of sequence information and limited analysis of gene function, the whi genes appear to be well conserved among streptomycetes.…”