Tissue‐specific glycogen branching isoenzymes in a multicellular prokaryote, Streptomyces coelicolor A3(2)

Abstract

In the overtly differentiated colonies of Streptomyces coelicolor A3(2), discrete phases of glycogen synthesis are found at the vegetative/aerial mycelium boundary (phase I) and in the immature spore chains at aerial hyphal tips (phase II). We have characterized two S. coelicolor glgB genes encoding glycogen branching enzyme, which are well separated in the genome. Disruption of glgBl led to the formation of abnormal polyglucan deposits at phase I, with phase II remaining normal, whereas disruption of glgBII interfered specifically with phase II deposits, and not with those of phase I. Thus, each branching enzyme isoform is involved in a different phase of glycogen synthesis. This situation contrasts with that in simple bacteria, which typically have a single set of enzymes for glycogen metabolism, and more closely resembles that in plants.

The interplay of glycogen metabolism and differentiation provides an insight into the developmental biology of Streptomyces coelicolor

“…The previously observed glycogen deposition phenotypes of the parental strain J1508 and its glgBI-and glgBIIdisrupted strains (J1861 and J1859 respectively) (Bruton et al, 1995; were confirmed. J1508 ( Fig.…”

“…Bruton et al (1995) observed similar structures when they disrupted either of two branching enzyme genes (glgBI and glgBII) in the model species Streptomyces coelicolor A3(2). Each S. coelicolor mutant was affected in just one phase of glycogen deposition.…”

“…On the other hand, the glgBII mutant displayed normal phase I deposition, but the phase II deposits were abnormal, occurring as small numbers of large blobs in the immature spore compartments of the aerial hyphae. The abnormal phase II deposits were less frequent, and much more regularly rounded in appearance, than the unbranched phase I deposits of the glgBI mutant (Bruton et al, 1995).…”

“…Transmission electron microscopy (TEM) has revealed two localized phases of net glycogen deposition during colony development (Braña et al, 1986;Bruton et al, 1995). Phase I deposits are found in a region of the substrate mycelium bordering the aerial mycelium, and phase II deposits are present in the apical compartments of the aerial mycelium as they are undergoing sporulation septation.…”

Forty years of genetics with Streptomyces: from in vivo through in vitro to in silico

“…Again, the discovery of two phases of glycogen deposition and hydrolysis, at different stages of the life cycle, and controlled by two sets of paralogous genes (Bruton et al, 1995), served to identify genes with a presumptive but indirect role in the developmental cycle which would not have been discovered by a simple search for mutants with a clear defect in morphogenesis.…”