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Differential expression of phosphorus acquisition genes in response to phosphorus stress in two Raphidiopsis raciborskii strains.
Harmful Algae ( IF 6.6 ) Pub Date : 2018-12-30 , DOI: 10.1016/j.hal.2018.12.003
Anusuya Willis 1 , Ann W Chuang 1 , Sonya Dyhrman 2 , Michele A Burford 1
Affiliation  

The cyanobacterium Raphidiopsis raciborskii is a nuisance in freshwater ecosystems. Strains vary in their physiological responses to environmental drivers, thus a greater understanding of the magnitude of strain variation is required to characterize the species. In this study, two strains of R. raciborskii isolated from a tropical Australian water reservoir were grown with and without phosphorus (P) to determine any relative response to P stress. The strains had the same growth rates and under P free conditions, cells grew at the same rate as P replete conditions until day 9 when cell growth ceased. There was no difference in the alkaline phosphatase activity per cell for the P replete and P free conditions, but the level of activity per cell was greater in CS-505 than CS-506. P acquisition genes were identified from the sequenced genomes; both strains contained the same genes, but with differences in copy number of phoA (7 and 6), phnK (3 and 1) and phnH (2 and 1) between CS-505 and CS-506 (respectively). The expression of P acquisition genes under P stress was measured throughout the experiment and shown to vary in magnitude and timing across strains, and in P replete versus P free cultures. In strain CS-505, upregulation of the pstS1 and phoA genes occurred late in the growth phase and into senescence. These genes are involved in phosphate uptake and use of various forms of organic P. For strain CS-506, there was upregulation of the phosphate uptake gene, pit, and organic P utilization genes, phoA, phoU, phnD and phnK, commencing late in the growth phase. Our study shows that despite the fact that these two strains were isolated from the same waterbody, they differed markedly in their gene expression response to P free conditions. This capacity of R. raciborskii to vary in strain responses to P conditions gives the organism flexibility in responding to environmental change, particularly P stress conditions.



中文翻译:

在两个Raphidiopsis raciborskii菌株中响应磷胁迫的磷获取基因的差异表达。

蓝藻Raphidiopsis raciborskii对淡水生态系统是有害的。菌株对环境驱动器的生理反应各不相同,因此需要对菌株变异的大小有更深入的了解才能表征该菌种。在这项研究中,R。raciborskii的两个菌株在有和没有磷(P)的条件下,从澳大利亚热带水库中分离出的磷,以确定对磷胁迫的任何相对响应。菌株具有相同的生长速率,在无磷条件下,细胞以与富磷条件相同的速率生长,直到第9天细胞生长停止。在P充足和无P条件下,每个细胞的碱性磷酸酶活性没有差异,但是CS-505中的每个细胞的活性水平高于CS-506。从测序的基因组中鉴定出P个采集基因;两种菌株均含有相同的基因,但phoA(7和6),phnK(3和1)和phnH的拷贝数不同(分别在CS-505和CS-506之间)(2和1)。在整个实验过程中都测量了P胁迫下P采集基因的表达,结果表明,在菌株之间以及在P充分培养与无P培养条件下,P捕获基因的大小和时间均发生变化。在菌株CS-505中,pstS1phoA基因的上调发生在生长期后期,并进入衰老。这些基因参与磷酸盐摄取和利用各种形式的有机P的对于菌株CS-506,有磷酸盐摄取基因的上调坑,和有机磷利用基因,phoA启动,普山,phnDphnK,从成长阶段的后期开始。我们的研究表明,尽管事实上这两个菌株是从相同的水体中分离出来的,但它们对无磷条件的基因表达反应却存在显着差异。R. raciborskii对菌株在P胁迫条件下的响应能力有所变化,这赋予了生物体应对环境变化(尤其是P胁迫条件)的灵活性。

更新日期:2018-12-30
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