Isoprene synthase (IspS) is the sole enzyme in plants responsible for the yearly emission in the atmosphere of thousands of tonnes of the natural hydrocarbon isoprene worldwide. Species of the monocotyledonous family Arecaceae (palms) are among the highest plant emitters, but to date no IspS gene from this family has been identified. Here, we screened with PTR‐ToF‐MS 18 genera of the Arecaceae for isoprene emission and found that the majority of the sampled species emits isoprene. Putative IspS genes from six different genera were sequenced and three of them were functionally characterized by heterologous overexpression in Arabidopsis thaliana, demonstrating that they encode functional IspS genes. Site‐directed mutagenesis and expression in Arabidopsis demonstrated the functional relevance of a novel IspS diagnostic tetrad from Arecaceae, whose most variable amino acids could not preserve catalytic function when substituted by a putatively dicotyledonous‐specific tetrad. In particular, mutation of threonine 479 likely impairs the open–closed transition of the enzyme by altering the network of hydrogen bonds between helices H1α, H, and I. These results shed new light on the evolution of IspS in monocots, suggesting that isoprene emission is an ancestral trait within the Arecaceae family. The identification of IspS from Arecaceae provides promising novel enzymes for the production of isoprene in heterologous systems and allows the screening and selection of commercially relevant palm varieties with lower environmental impact.

中文翻译：

---

槟榔科（棕榈科）异戊二烯排放的演变


异戊二烯合酶 (IspS) 是植物中唯一的酶，每年在全球范围内向大气中排放数千吨天然碳氢化合物异戊二烯。单子叶植物科槟榔科（棕榈科）的物种是排放量最高的植物之一，但迄今为止尚未鉴定出来自该科的IspS基因。在这里，我们利用 PTR-ToF-MS 对槟榔科 18 个属的异戊二烯排放进行了筛选，发现大多数采样物种都排放异戊二烯。对来自六个不同属的假定IspS基因进行了测序，其中三个在拟南芥中通过异源过度表达进行了功能表征，证明它们编码功能性 IspS 基因。拟南芥中的定点诱变和表达证明了来自槟榔科的新型 IspS 诊断四分体的功能相关性，其大多数可变氨基酸在被假定的双子叶植物特异性四分体取代时无法保留催化功能。特别是，苏氨酸 479 的突变可能通过改变螺旋 H1α、H 和 I 之间的氢键网络来损害酶的开闭转变。这些结果为单子叶植物中 IspS 的进化提供了新的线索，表明异戊二烯的发射是槟榔科家族的祖先特征。来自槟榔科的 IspS 的鉴定为在异源系统中生产异戊二烯提供了有前途的新型酶，并允许筛选和选择具有较低环境影响的商业相关棕榈品种。