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Updated: Dec 20, 2025

Generation of Marked and Markerless Mutants in Model Cyanobacterial Species
Published on: May 29, 2016
NsiR1, a small RNA with multiple copies, modulates heterocyst differentiation in the cyanobacterium Nostoc sp. PCC
Manuel Brenes-Álvarez1, Marina Minguet1, Agustín Vioque1
1Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas and Universidad de Sevilla, Sevilla, Spain.
Abstract:
Upon nitrogen starvation, filamentous cyanobacteria develop heterocysts, specialized cells devoted to the fixation of atmospheric nitrogen. Differentiation of heterocyst at semi-regular intervals along the filaments requires complex structural and functional changes that are under the control of the master transcriptional regulator HetR. NsiR1 (nitrogen stress-induced RNA 1) is a HetR-dependent non-coding RNA that is expressed specifically in heterocysts from a very early stage of differentiation. In the genome of Nostoc sp. PCC 7120 there are 12 tandem copies of nsiR1 (nsiR1.1 to nsiR1.12), seven of them with identical sequence (nsiR1.3 to nsiR1.9) and the others slightly divergent. nsiR1.1 is transcribed antisense to the 5' UTR of hetF, a gene required for heterocyst development. Here, we show that binding of NsiR1.1 inhibits translation of the hetF mRNA by inducing structural changes in its 5' UTR. Altered levels of NsiR1 result in different phenotypic alterations including enlarged cell size and delayed heterocyst development that could be related to a reduced amount of HetF.
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