Department of Herbal Crop Research, National Institute of Horticultural and Herbal Science, Rural Development Administration, Eumseong 27709, Korea.
Catholic Kwandong University International St. Mary's Hospital, Incheon 22711, Korea.
Genes (Basel). 2021 May 31;12(6):848. doi: 10.3390/genes12060848.
Various fungi including , an entomopathogenic fungus, can produce steroidal triterpenoids. Protostadienol (protosta-17(20)Z,24-dien-3β-ol) is a precursor of steroidal triterpenoid compounds. To identify oxidosqualene cyclase (OSC) gene candidates involved in triterpenoid biosynthesis, genome mining was performed using Illumina sequencing platform. In the sequence database, two OSC genes, and , in the genome of were identified. Predicted amino-acid sequences of CfaOSC2 shared 66% similarities with protostadienol synthase (OSPC) of . Phylogenetic analysis showed a clear grouping of CfaOSC2 in the OSPC clade. Function of CfaOSC2 was examined using a yeast INVSc1 heterologous expression system to endogenously synthesize 2,3-oxidosqualene. GC-MS analysis indicated that CfaOSC2 produced protosta-13(17),24-dien-3β-ol and protostadienol at a 5:95 ratio. Our results demonstrate that CfaOSC2 is a multifunctional triterpene synthase yielding a predominant protostadienol together with a minor triterpenoid. These results will facilitate a greater understanding of biosynthetic mechanisms underlying steroidal triterpenoid biosynthesis in and other fungi.
各种真菌，包括一种昆虫病原真菌，可以产生甾体三萜类化合物。原甾醇（protosta-17(20)Z,24-二烯-3β-醇）是甾体三萜类化合物的前体。为了鉴定参与三萜类生物合成的角鲨烯环氧化酶（OSC）基因候选物，使用 Illumina 测序平台对基因组进行了挖掘。在序列数据库中，从 基因组中鉴定出了两个 OSC 基因 和 。CfaOSC2 的预测氨基酸序列与 的原甾醇合酶（OSPC）共享 66%的相似性。系统发育分析表明，CfaOSC2 在 OSPC 分支中明显分组。使用酵母 INVSc1 异源表达系统来内源性合成 2,3-氧化鲨烯，以检验 CfaOSC2 的功能。GC-MS 分析表明，CfaOSC2 以 5:95 的比例产生原甾醇-13(17),24-二烯-3β-醇和原甾醇。我们的结果表明，CfaOSC2 是一种多功能的三萜合成酶，主要产生原甾醇，同时产生少量三萜类化合物。这些结果将有助于更好地理解 和其他真菌中甾体三萜类生物合成的生物合成机制。
