Two Genes Encoding Protein Kinases of the HstK Family Are Involved in Synthesis of the Minor Heterocyst-Specific Glycolipid in the Cyanobacterium Anabaena sp. Strain PCC 7120
Two Genes Encoding Protein Kinases of the HstK Family Are Involved in Synthesis of the Minor Heterocyst-Specific Glycolipid in the Cyanobacterium Anabaena sp. Strain PCC 7120
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DOI：
10.1128/jb.00323-07
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发表时间：
2007-05
影响因子：
3.2
通讯作者：
Lei Shi;Jian-hong Li;Yong Cheng-;Li Wang;Wen-Li Chen;Cheng‐Cai Zhang
中科院分区：
文献类型：
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作者：
Lei Shi;Jian-hong Li;Yong Cheng-;Li Wang;Wen-Li Chen;Cheng‐Cai Zhang
摘要丝状蓝藻鱼腥藻PCC 7120能在有氧条件下固氮，固氮活性仅发生在异形胞中，异形胞是由营养细胞分化而来的细胞，对培养基中结合氮源的限制作出反应。在异形胞分化的后期，形成由两种糖脂组成的包膜层，以限制氧的进入，从而使氧敏感固氮酶能够发挥作用。鱼腥藻菌株PCC 7120的基因组具有13个基因的家族（hstK家族），所有基因编码的蛋白质在其N末端具有推定的Ser/Thr激酶结构域，在其C末端具有His激酶结构域。在这项研究中，我们发现，双突变D4.3菌株，其中该基因家族的两个成员，pkn 44（all 1625）和pkn 30（all 3691），都失活，未能固定N2在氧气（福克斯-）的存在下。在无氧环境中，可检测到低水平的固氮酶活性（Fix+）。突变体D4.3中的异形胞发育延迟了24小时，并在相对较早的阶段停止，而没有糖脂层（Hgl−）的形成。只有少数物种的两个杂囊特异性糖脂（HGL）的突变体中失踪。我们建议，DevH，一个假定的转录因子，协调两个HGL的合成，而Pkn 44/Pkn 30和先前表征的PrpJ可能代表两个不同的调节途径参与合成的次要HGL和主要HGL，分别。
ABSTRACT The filamentous cyanobacterium Anabaena sp. strain PCC 7120 can fix N2 under oxic conditions, and the activity of nitrogen fixation occurs exclusively in heterocysts, cells differentiated from vegetative cells in response to a limitation of a combined-nitrogen source in the growth medium. At the late stages of heterocyst differentiation, an envelope layer composed of two glycolipids is formed to limit the entry of oxygen so that the oxygen-sensitive nitrogenase can function. The genome of Anabaena sp. strain PCC 7120 possesses a family of 13 genes (the hstK family), all encoding proteins with a putative Ser/Thr kinase domain at their N termini and a His-kinase domain at their C termini. In this study, we showed that the double mutant D4.3 strain, in which two members of this gene family, pkn44 (all1625) and pkn30 (all3691), were both inactivated, failed to fix N2 in the presence of oxygen (Fox−). In an environment without oxygen, a low level of nitrogenase activity was detectable (Fix+). Heterocyst development in the mutant D4.3 was delayed by 24 h and arrested at a relatively early stage without the formation of the glycolipid layer (Hgl−). Only the minor species of the two heterocyst-specific glycolipids (HGLs) was missing in the mutant. We propose that DevH, a putative transcription factor, coordinates the synthesis of both HGLs, while Pkn44/Pkn30 and the previously characterized PrpJ may represent two distinct regulatory pathways involved in the synthesis of the minor HGL and the major HGL, respectively.