Mylia taylorii is an ancient nonseed land plant that accumulates various sesquiterpenes with insecticidal and antibacterial activities. Recently, microbial-type sesquiterpene synthases (STSs) with atypical aspartate-rich metal ion binding motifs have been identified in some liverworts. Here, transcriptome analysis of M. taylorii was performed to identify M. taylorii sesquiterpene synthases (MtSTSs) that are potentially involved in sesquiterpene biosynthesis and diversity. A total of 255,669 unigenes were obtained with an average length of 963 bp in the transcriptome data of M. taylorii, among which 148,093 (57.92%) unigenes had BLAST results. Forty-eight unigenes were related to the sesquiterpene backbone biosynthesis according to KEGG annotation. In addition, MtSTS1, MtSTS2 and MtSTS3 identified from putative MtSTSs display sesquiterpene catalytic activities on the basis of functional characterizations in yeast. Interestingly, MtSTSs exhibit a noncanonical metal ion binding motif and the structural composition of a single α-domain, which are features of microbial STSs instead of archetypical plant STSs. This study revealed new microbial-type STS members of nonseed plants, and functionally identified that MtSTSs may contribute to the investigation of the biosynthesis and biological role of sesquiterpenes in M. taylorii.

Mylia taylorii是一种古老的非种子陆地植物，积累了多种具有杀虫和抗菌活性的倍半萜。近来，在一些艾草中已鉴定出具有非典型的富含天冬氨酸的金属离子结合基序的微生物型倍半萜烯合酶（STS）。这里，转录组分析M. taylorii以鉴定M. taylorii倍半萜合酶（MtSTSs），它们可能参与生物合成倍半萜烯和多样性。在taylorii的转录组数据中，总共获得255,669个单基因，平均长度为963 bp 。，其中148,093（57.92％）个单基因具有BLAST结果。根据KEGG的注释，有48个单基因与倍半萜骨架的生物合成有关。此外，根据酵母的功能特征，从推定的MtSTS中鉴定出的MtSTS1，MtSTS2和MtSTS3表现出倍半萜烯催化活性。有趣的是，MtSTS表现出非规范的金属离子结合基序和单个α结构域的结构组成，这是微生物STS而非原型植物STS的特征。这项研究揭示了非种子植物中新的微生物型STS成员，并在功能上确定MtSTSs可能有助于研究倍半萜在taylorii中的生物合成和生物学作用。