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.

中文翻译：

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NsiR1是一种具有多个拷贝的小RNA，可调节蓝细菌Nostoc sp。中的杂种囊分化。PCC 7120。

氮饥饿时，丝状蓝细菌会形成异型囊，即专门用于固定大气氮的细胞。沿细丝以半规则间隔分化异胚囊需要复杂的结构和功能变化，这些变化在主转录调节因子HetR的控制下进行。NsiR1（Ñ itrogen小号tress-我EP3受体激动剂诱导ř NA 1）是特别在异形从分化的非常早的阶段中表达的HetR依赖性非编码RNA。在Nostoc sp。的基因组中。7120有12个串联拷贝nsiR1（nsiR1。1至nsiR1。12），其中七具有相同序列（nsiR1。3至nsiR1。9），其他稍微发散。nsiR1。1被反义转录为hetF的5'UTR，hetF是异囊发育所需的基因。在这里，我们显示NsiR1.1的结合通过在其5'UTR中诱导结构变化来抑制hetF mRNA的翻译。NsiR1水平的改变会导致不同的表型改变，包括细胞大小增加和异囊发育延迟，这可能与HetF的减少有关。