title: Mutations in four regulatory genes have interrelated effects on heterocyst maturation in Anabaena sp. strain PCC 7120.
abstract: Regulatory genes hepK, hepN, henR, and hepS are required for heterocyst maturation in Anabaena sp. strain PCC 7120. They presumptively encode two histidine kinases, a response regulator, and a serine/threonine kinase, respectively. To identify relationships between those genes, we compared global patterns of gene expression, at 14 h after nitrogen step-down, in corresponding mutants and in the wild-type strain. Heterocyst envelopes of mutants affected in any of those genes lack a homogeneous, polysaccharide layer. Those of a henR mutant also lack a glycolipid layer. patA, which encodes a positive effector of heterocyst differentiation, was up-regulated in all mutants except the hepK mutant, suggesting that patA expression may be inhibited by products related to heterocyst development. hepS and hepK were up-regulated if mutated and so appear to be negatively autoregulated. HepS and HenR regulated a common set of genes and so appear to belong to one regulatory system. Some nontranscriptional mechanism may account for the observation that henR mutants lack, and hepS mutants possess, a glycolipid layer, even though both mutations down-regulated genes involved in formation of the glycolipid layer. HepK and HepN also affected transcription of a common set of genes and therefore appear to share a regulatory pathway. However, the transcript abundance of other genes differed very significantly from expression in the wild-type strain in either the hepK or hepN mutant while differing very little from wild-type expression in the other of those two mutants. Therefore, hepK and hepN appear to participate also in separate pathways.
authors.affiliation: MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, 48824-1312, USA.
authors.forename: Sigal
authors.initials: S
authors.lastname: Lechno-Yossef
authors.forename: Qing
authors.initials: Q
authors.lastname: Fan
authors.forename: Shigeki
authors.initials: S
authors.lastname: Ehira
authors.forename: Naoki
authors.initials: N
authors.lastname: Sato
authors.forename: C Peter
authors.initials: CP
authors.lastname: Wolk
mesh_terms: D017033:Anabaena / Q000737:chemistry / Q000235:genetics* / Q000254:growth & development; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology; D017353:Gene Deletion; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D005809:Genes, Regulator; D006017:Glycolipids / Q000032:analysis; D020411:Oligonucleotide Array Sequence Analysis; D011135:Polysaccharides, Bacterial / Q000032:analysis; D012329:RNA, Bacterial / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D018085:Regulon / Q000235:genetics; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D006017:Glycolipids; C113959:HepK protein, Anabaena; D011135:Polysaccharides, Bacterial; D012329:RNA, Bacterial; D012333:RNA, Messenger