Unicellular algae have evolved to express many forms of high-affinity phosphate transporters, and homologs of these proteins are broadly distributed in yeast, fungi, higher plants, and vertebrates. In this report, an effort has been made to characterize such a transporter gene, StPHO , in the marine diatom Skeletonema tropicum . The primers used for polymerase chain reaction were designed by referring to a homologous gene in a prasinophyte, and the full-length (1692 bp) cDNA of StPHO was then cloned and sequenced. Sequence alignments and secondary structure prediction indicated that StPHO is a gene that encodes a type III Na + /Pi cotransporter (SLC20 family). To study the function of StPHO , specific concentrations of inorganic phosphate (Pi) were used to alter the physiological status of S. tropicum . In each treatment, samples were collected for the measurements of StPHO mRNA, [PO 4 3− ], cell abundance, the maximal photochemical efficiency of photosystem II ( F v / F m ), and alkaline phosphatase activity (APA). The results indicated that the ambient [PO 4 3− ] strongly affected the population growth and related physiological parameters of S. tropicum . The transcription of StPHO was fully repressed when the [PO 4 3− ] was greater than 1 μM but increased approximately 100-fold when the ambient [PO 4 3− ] decreased to 0.02 μM. Within this [PO 4 3− ] range, the regression equations are Y = −0.6644 X + 0.9034 and Y = −0.5908 X + 0.8054 for Pi-starved and Pi-limited treatments, respectively. This trend of gene expression suggested that StPHO plays an important role in the uptake of [PO 4 3− ], and StPHO may serve as a useful molecular biomarker for Pi-stressed diatom populations in marine ecosystems.

中文翻译：

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海洋硅藻热带拟南芥中推断的Na + / Pi共转运蛋白基因的序列比较和表达分析

单细胞藻类已经进化为表达多种形式的高亲和力磷酸盐转运蛋白，这些蛋白的同源物广泛分布于酵母，真菌，高等植物和脊椎动物中。在该报告中，已经做出了努力来表征海洋硅藻Skeletonema tropicum中的这种转运蛋白基因StPHO。通过参照植物植物中的同源基因设计用于聚合​​酶链反应的引物，然后克隆并测序StPHO的全长（1692 bp）cDNA。序列比对和二级结构预测表明StPHO是编码III型Na + / Pi共转运蛋白（SLC20家族）的基因。为了研究StPHO的功能，使用特定浓度的无机磷酸盐（Pi）来改变热带链球菌的生理状态。在每次治疗中 收集样品用于测量StPHO mRNA，[PO 4 3-]，细胞丰度，光系统II的最大光化学效率（Fv / Fm）和碱性磷酸酶活性（APA）。结果表明，环境[PO 4 3-]强烈影响热带链球菌的种群生长和相关的生理参数。当[PO 4 3-]大于1μM时，StPHO的转录被完全抑制，但是当环境[PO 4 3-]降低至0.02μM时，StPHO的转录增加约100倍。在此[PO 4 3-]范围内，Pi饥饿和Pi限制处理的回归方程分别为Y = -0.6644 X + 0.9034和Y = -0.5908 X + 0.8054。这种基因表达趋势表明StPHO在摄取[PO 4 3-]中起重要作用，