Essential role of DivlVA in polar growth and morphogenesis in Streptomyces coelicolor A3(2)

Abstract

Streptomycetes grow by cell wall extension at hyphal tips. The molecular basis for such polar growth in prokaryotes is largely unknown. It is reported here that DivlVASC, the Streptomyces coelicolor homologue of the Bacillus subtilis protein DivlVA, is essential and directly involved in hyphal tip growth and morphogenesis. A DivlVASC-EGFP hybrid was distinctively localized to hyphal tips and lateral branches. Reduction of divlVASC expression to about 10% of the normal level produced a phenotype strikingly similar to that of many tip growth mutants in fungi, including irregular curly hyphae and apical branching. Overexpression of the gene dramatically perturbed determination of cell shape at the growing tips. Furthermore, staining of nascent peptidoglycan with a fluorescent vancomycin conjugate revealed that induction of overexpression in normal hyphae disturbed tip growth, and gave rise to several new sites of cell wall assembly, effectively causing hyperbranching. The results show that DivlVASC is a novel bacterial morphogene, and it is localized at or very close to the apical sites of peptidoglycan assembly in Streptomyces hyphae.