The importance of the metabolic route of nitrogen in the fungus Penicillium rubens (strain PO212) is studied in relation to its biocontrol activity (BA). PO212 can resist a high concentration of chlorate anion and displays a classical nitrate-deficiency (nit-) phenotype resulting in poor colonial growth when nitrate is used as the main source of nitrogen. Analyses of genes implicated in nitrate assimilation evidenced the strong sequence conservation of PO212 and CH8 genome with penicillin producers such as reference strain P. rubens Wisconsin 54-1255, P2niaD18 and Pc3, however also revealed the presence of mutations. PO212 carries a mutation in the gene coding for zinc-binuclear cluster transcription factor NirA that specifically mediates the regulation of genes involved in nitrate assimilation. The nirA1 mutation causes an early stop of NirA factor, losing 66% of its sequence. The NirA1 mutant form is unable to mediate a nitrate-dependent regulation of nitrate and nitrite reductase coding genes. In this study, we study another isolate, CH8, with potential BA and nit- phenotype. A mutation in the nitrate permease coding gene crnA was found in CH8. An insertion of a guanine in the coding sequence cause a frameshift in CrnA with the loss of the last two transmembrane domains. Analysis of PO212 and CH8 isolates and complementation strains show the importance of NirA regulator in maintaining correct transcriptional levels of nitrate and nitrite reductases and suggest CrnA as the main nitrate transporter. the presence of alternative transporter for chlorate and the existence of a mechanism for preventing nitrite derived toxicity in Penicillum. BA of PO212 is partially altered when nirA1 mutation was complemented. This result and the finding of CH8, a novel biocontrol P. rubens strain with a nit- phenotype, suggest that nitrogen metabolism is a component of biocontrol capacity.

中文翻译：

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青霉生物防治菌株中氮代谢的改变。

研究了真菌青霉（菌株PO212）中氮的代谢途径的重要性及其生物防治活性（BA）。当将硝酸盐用作主要的氮源时，PO212可以抵抗高浓度的氯酸根阴离子并表现出经典的硝酸盐缺乏症（nit-）表型，导致菌落生长较差。对涉及硝酸盐同化的基因的分析表明，青霉素生产者（如参考菌株鲁本斯·威斯康星州54-1255，P2niaD18和Pc3）的青霉素生产者PO212和CH8基因组具有很强的序列保守性，但同时也揭示了突变的存在。PO212在编码锌-双核簇转录因子NirA的基因中携带一个突变，该突变专门介导涉及硝酸盐同化的基因的调控。nirA1突变导致NirA因子的早期终止，丢失其序列的66％。NirA1突变体形式不能介导硝酸盐和亚硝酸盐还原酶编码基因的硝酸盐依赖性调节。在这项研究中，我们研究了另一种可能具有BA和非表型的分离株CH8。在CH8中发现了硝酸盐渗透酶编码基因crnA的突变。在编码序列中插入鸟嘌呤会导致CrnA移码，并丢失最后两个跨膜结构域。对PO212和CH8分离株和互补菌株的分析显示NirA调节剂在维持正确的硝酸盐和亚硝酸还原酶转录水平方面的重要性，并暗示CrnA是主要的硝酸盐转运蛋白。氯酸盐替代转运蛋白的存在以及防止青霉素中亚硝酸盐衍生毒性的机制的存在。当nirA1突变被互补时，PO212的BA被部分改变。这一结果和发现的一种新型的具有对照表型的生防锈假单胞菌CH8 CH8的发现表明，氮代谢是生防能力的一个组成部分。