Metal transport processes are relatively poorly understood in algae in comparison to higher plants and other eukaryotes. A screen of genomes from 33 taxonomically diverse algal species was conducted to identify members of the Cation Diffusion Facilitator (CDF) family of metal ion transporter. All algal genomes contained at least one CDF gene with four species having >10 CDF genes (median of 5 genes per genome), further confirming that this is a ubiquitous gene family. Phylogenetic analysis suggested a CDF gene organisation of five groups, which includes Zn-CDF, Fe/Zn-CDF and Mn-CDF groups, consistent with previous phylogenetic analyses, and two functionally undefined groups. One of these undefined groups was algal specific although excluded chlorophyte and rhodophyte sequences. The majority of sequences (22 out of 26 sequences) from this group had a putative ion binding site motif within transmembrane domain 2 and 5 that was distinct from other CDF proteins, such that alanine or serine replaced the conserved histidine residue. The phylogenetic grouping was supported by sequence cluster analysis. Yeast heterologous expression of CDF proteins from Chlamydomonas reinhardtii indicated Zn2+ and Co2+ transport function by CrMTP1, and Mn2+ transport function by CrMTP2, CrMTP3 and CrMTP4, which validated the phylogenetic prediction. However, the Mn-CDF protein CrMTP3 was also able to provide zinc and cobalt tolerance to the Zn- and Co-sensitive zrc1 cot1 yeast strain. There is wide diversity of CDF transporters within the algae lineage, and some of these genes may be attractive targets for future applications of metal content engineering in plants or microorganisms.

中文翻译：

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藻类中阳离子扩散促进剂转运蛋白的多基因组分析。

与高等植物和其他真核生物相比，藻类中的金属运输过程了解相对较少。筛选了来自33种分类学不同的藻类的基因组，以鉴定金属离子转运蛋白阳离子扩散促进剂（CDF）家族的成员。所有藻类基因组均包含至少一个CDF基因，以及四个具有> 10个CDF基因的物种（每个基因组5个基因的中位数），进一步证实了这是一个普遍存在的基因家族。系统发育分析表明，CDF基因的组织由五个组组成，其中包括Zn-CDF，Fe / Zn-CDF和Mn-CDF组，这与以前的系统发育分析一致，另外还有两个功能不确定的组。这些不确定的组之一是藻类特异性的，尽管排除了绿藻类和红藻类序列。该组中的大多数序列（26个序列中的22个）在跨膜结构域2和5中具有一个推定的离子结合位点基序，与其他CDF蛋白不同，因此丙氨酸或丝氨酸取代了保守的组氨酸残基。系统发育分组得到序列聚类分析的支持。莱茵衣藻CDF酵母的异源表达表明CrMTP1具有Zn2 +和Co2 +转运功能，而CrMTP2，CrMTP3和CrMTP4具有Mn2 +转运功能，这证明了系统发育预测。但是，Mn-CDF蛋白CrMTP3也能够为Zn和Co敏感的zrc1 cot1酵母菌株提供锌和钴耐受性。藻类谱系中CDF转运蛋白的种类繁多，