Expression of cyanobacterial genes involved in heterocyst differentiation and dinitrogen fixation along a plant symbiosis development profile.
Members of the cyanobiont genus Nostoc, forming an endosymbiosis with members of the angiosperm genus Gunnera, undergo a number of characteristic phenotypic changes during the development of the symbiosis, the genetic background of which is largely unknown. Transcription patterns of genes related to heterocyst differentiation and dinitrogen fixation and corresponding protein profiles were examined, using reverse transcription-polymerase chain reaction and Western blots, along a developmental (apex to mature parts) sequence in Gunnera magellanica and G. manicata and under mimicked symbiotic conditions in a free-living Gunnera isolate (Nostoc strain 0102). The hetR gene was highly expressed and correlated positively with an increase in heterocyst frequency and with ntcA expression, whereas nifH expression was already high close to the growing apex and glnB (P(II)) expression decreased along the symbiotic profile. Although gene expression appeared to be regulated to a large extent in the same fashion as in free-living cyanobacteria, significant differences were apparent, such as the overexpression of both hetR and ntcA and the contrasting down-regulation of glnB, features indicating important regulatory differences between symbiotic and free-living cyanobacteria. The significance of these findings is discussed in a symbiotic context.
Wang
Chun-Mei
CM
Department of Biological Pharmaceutics, School of Chinese Pharmacy, Beijing University of Chinese Medicine, 100029 Beijing, China.
Ekman
Martin
M
Bergman
Birgitta
B
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D000458:Cyanobacteria / Q000235:genetics* / Q000254:growth & development* / Q000502:physiology; D004269:DNA, Bacterial / Q000235:genetics; D005632:Fructose / Q000494:pharmacology; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D005798:Genes, Bacterial; D019684:Magnoliopsida / Q000382:microbiology*; D008717:Methionine Sulfoximine / Q000494:pharmacology; D009586:Nitrogen Fixation / Q000235:genetics; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D051922:PII Nitrogen Regulatory Proteins; D010641:Phenotype; D013559:Symbiosis / Q000235:genetics
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D051922:PII Nitrogen Regulatory Proteins; C067403:HetR protein, Bacteria; D008717:Methionine Sulfoximine; D005632:Fructose; C404143:PIID regulatory protein, Bacteria; D010088:Oxidoreductases; C029130:nitrogenase reductase