Dimethylsulfoniopropionate (DMSP) is a globally important organosulfur molecule and the major precursor for dimethyl sulfide. These compounds are important info-chemicals, key nutrients for marine microorganisms, and are involved in global sulfur cycling, atmospheric chemistry and cloud formation^1-3. DMSP production was thought to be confined to eukaryotes, but heterotrophic bacteria can also produce DMSP through the pathway used by most phytoplankton ⁴ , and the DsyB enzyme catalysing the key step of this pathway in bacteria was recently identified ⁵ . However, eukaryotic phytoplankton probably produce most of Earth's DMSP, yet no DMSP biosynthesis genes have been identified in any such organisms. Here we identify functional dsyB homologues, termed DSYB, in many phytoplankton and corals. DSYB is a methylthiohydroxybutryate methyltransferase enzyme localized in the chloroplasts and mitochondria of the haptophyte Prymnesium parvum, and stable isotope tracking experiments support these organelles as sites of DMSP synthesis. DSYB transcription levels increased with DMSP concentrations in different phytoplankton and were indicative of intracellular DMSP. Identification of the eukaryotic DSYB sequences, along with bacterial dsyB, provides the first molecular tools to predict the relative contributions of eukaryotes and prokaryotes to global DMSP production. Furthermore, evolutionary analysis suggests that eukaryotic DSYB originated in bacteria and was passed to eukaryotes early in their evolution.

中文翻译：

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DSYB催化许多浮游植物中丙酸二甲酯的生物合成的关键步骤。

丙酸二甲酯（DMSP）是全球重要的有机硫分子，是二甲基硫的主要前体。这些化合物是重要的信息化学品，海洋微生物的关键营养物质，并参与全球硫循环，大气化学和云的形成^1-3。DMSP的产生被认为仅限于真核生物，但异养细菌也可以通过大多数浮游植物所使用的途径产生DMSP ⁴，最近发现了DsyB酶催化了细菌中该途径的关键步骤⁵。但是，真核浮游植物可能会产生地球上大部分的DMSP，但在任何此类生物中均未发现DMSP生物合成基因。在这里，我们在许多浮游植物和珊瑚中鉴定了功能性dsyB同源物，称为DSYB。DSYB是一种甲基硫代羟丁酸甲基转移酶，位于触角植物小球藻的叶绿体和线粒体中，稳定的同位素跟踪实验支持这些细胞器作为DMSP合成的位点。在不同的浮游植物中，DSYB转录水平随DMSP浓度的增加而增加，并指示细胞内DMSP。真核生物DSYB序列以及细菌dsyB的鉴定为预测真核生物和原核生物对全球DMSP生产的相对贡献提供了第一个分子工具。此外，