Genomics of Terpene Biosynthesis in Dictyoceratid Sponges (Porifera) – What Do We (not) Know?

Sponges are recognized as promising sources for novel bioactive metabolites. Among them are terpenoid metabolites that constitute key biochemical defense mechanisms in several sponge taxa. Despite their significance, the genetic basis for terpenoid biosynthesis in sponges remains poorly understood. Dictyoceratida comprise demosponges well-known for their bioactive terpenoids. In this study, we checked the currently available genomic data for insights into the metabolic pathways of dictyoceratid terpenoids. We first identified prenyltransferase (PT) and terpene cyclase (TC) enzymes essential for the terpenoid biosynthetic processes in the terrestrial realm by analyzing available transcriptomic and genomic data of Dictyoceratida sponges and 10 other sponge species. All Dictyoceratida sponges displayed various PTs involved in either sesqui- or diterpene, steroid and carotenoid production. Additionally, it was possible to identify a potential candidate for a dictyoceratid sesterterpene PT. However, analogs of common terrestrial TCs were absent, suggesting the existence of a distinct or convergently evolved sponge-specific TC. Our study aims to contribute to the foundational understanding of terpene biosynthesis in sponges, unveiling the currently evident genetic components for terpenoid production in species not previously studied. Simultaneously, it aims to identify the known and unknown factors, as starting point for biochemical and genetic investigations in sponge terpenoid production.

海绵被公认为新型生物活性代谢物的极具潜力的来源。其中萜类代谢物是诸多海绵类群关键生化防御机制的核心组成部分。尽管萜类代谢物意义重大，但海绵中萜类生物合成的遗传基础仍有待深入解析。
网角海绵目（Dictyoceratida）包含以产生活性萜类化合物而闻名的寻常海绵纲（demosponges）物种。本研究通过梳理现有公开基因组数据，旨在解析网角海绵目萜类化合物的代谢通路。
研究首先通过分析网角海绵目海绵及另外10种海绵的转录组与基因组数据，鉴定出陆生环境中萜类生物合成过程所必需的异戊烯基转移酶（prenyltransferase, PT）与萜环化酶（terpene cyclase, TC）。所有网角海绵目海绵均携带多种异戊烯基转移酶，分别参与倍半萜/二萜、类固醇及类胡萝卜素的生物合成。此外，本研究还成功鉴定出一种潜在的网角海绵目二倍半萜异戊烯基转移酶候选蛋白。
然而，研究未发现常见陆生萜环化酶的同源蛋白，这暗示存在一类独特的、或经趋同进化而来的海绵特异性萜环化酶。本研究旨在为海绵萜类生物合成的基础认知提供新的科学依据，揭示此前未被研究的海绵物种中萜类合成的现有遗传组分；同时，本研究也旨在明确相关已知与未知因子，为海绵萜类合成的生化与遗传学研究提供起点。