Nostopeptolide plays a governing role during cellular differentiation of the symbiotic cyanobacterium Nostoc punctiforme

Abstract

Nostoc punctiforme is a versatile cyanobacterium that can live either independently or in symbiosis with plants from distinct taxa. Chemical cues from plants and N. punctiforme were shown to stimulate or repress, respectively, the differentiation of infectious motile filaments known as hormogonia. We have used a polyketide synthase mutant that accumulates an elevated amount of hormogonia as a tool to understand the effect of secondary metabolites on cellular differentiation of N. punctiforme. Applying MALDI imaging to illustrate the reprogramming of the secondary metabolome, nostopeptolides were identified as the predominant difference in the pks2 − mutant secretome. Subsequent differentiation assays and visualization of cell-type-specific expression of nostopeptolides via a transcriptional reporter strain provided evidence for a multifaceted role of nostopeptolides, either as an autogenic hormogonium-repressing factor or as a chemoattractant, depending on its extracellular concentration. Although nostopeptolide is constitutively expressed in the free-living state, secreted levels dynamically change before, during, and after the hormogonium differentiation phase. The metabolite was found to be strictly down-regulated in symbiosis with Gunnera manicata and Blasia pusilla, whereas other metabolites are up-regulated, as demonstrated via MALDI imaging, suggesting plants modulate the fine-balanced cross-talk network of secondary metabolites within N. punctiforme.

High-Density Cultivation of Terrestrial Nostoc Strains Leads to Reprogramming of Secondary Metabolome

“…Although the expression seemed rather cell type specific in C cultures and was apparently connected to early akinetes, the cell-specific restriction was abrogated in HD cultures. These data further strengthen the hypothesis that secondary metabolites are connected to cellular differentiation of N. punctiforme (11), although the specific role of anabaenopeptin in this network and the mechanistic basis underlying the expression pattern are currently unknown.…”

“…Specific primer pairs for each BGC were designed ( Table 2). The RNase P encoding gene rnpB was used as a housekeeping gene for standardization, as described previously (11). All primers were tested in PCRs prior to RT-PCR.…”

“…The genome of the model strain Nostoc punctiforme PCC 73102 harbors a large number of BGCs encoding nonribosomal peptide synthetases (NRPS) and polyketide synthases (PKS), as well as ribosomal natural product pathways (RiPPs). While at least two of the corresponding metabolites, nostopeptolide and the cryptic product of the pks2 pathway, have been linked to cellular differentiation recently (11,12), less is known about the impact of cell density on secondary metabolite production. Uncovering a potential connection is of considerable relevance, since cell density is a critical factor for secondary metabolite production in a large number of heterotrophic bacteria, including Streptomycetes, well known producers of potent antibiotics (13).…”

A Putative O-Linked β- N -Acetylglucosamine Transferase Is Essential for Hormogonium Development and Motility in the Filamentous Cyanobacterium Nostoc punctiforme

“…What is currently known about hormogonium development comes primarily from studies on the model filamentous cyanobacterium N. punctiforme. In wild-type N. punctiforme strains, a constitutive level of hormogonia develops under standard growth conditions, but a number of factors can positively or negatively affect hormogonium differentiation, including putative autogenic repressors and signals from symbiotic plant partners (10)(11)(12)(13)(14).…”

Mapeamento de agrupamentos gênicos envolvidos na fixação biológica de nitrogênio em genomas de isolados brasileiros de cianobactérias

“…A molécula doadora de elétrons para a fotossíntese também pode sofrer variações dentro do grupo, de modo que algumas cianobactérias são hábeis em utilizar sulfeto no lugar de água, em condições anaeróbicas (CASTENHOLZ; WATERBURY, 1989;COHEN et al, 1986 (MOORE et al, 1984;NAMIKOSHI;RINEHART, 1996;BURJA et al, 2001;ETCHEGARAY et al, 2004, SILVA-STENICO et al, 2011, LEÃO et al, 2012, LIAIMER et al, 2015.…”