Institute of Medicinal Plant Development, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, 100193, People's Republic of China.
Sci Rep. 2017 Mar 22;7(1):316. doi: 10.1038/s41598-017-00445-9.
Content determination and microscopic observation proved that dendrobine accumulation in the stem of Dendrobium nobile Lindl. increased after infection with mycorrhizal fungus MF23 (Mycena sp.). Large-scale transcriptome sequencing of symbiotic and asymbiotic D. nobile revealed that 30 unigenes encoding proteins were possibly related to the biosynthesis of dendrobine sesquiterpene backbone. A qRT-PCR experiment of 16 unigenes, selected randomly, proved that there were significant changes in the expression levels of AACT, MVD, PMK and TPS21 at 9 weeks after inoculation. These results implied that MF23 might stimulate dendrobine biosynthesis by regulating the expressions of genes involved in the mevalonate (MVA) pathway. The biogenetic pathway of dendrobine was suggested systematically according to the structural features of dendrobine alkaloids and their sesquiterpene precursors, which implied that post-modification enzymes might play a major role in dendrobine biosynthesis. Thus, genes encoding post-modification enzymes, including cytochrome P450, aminotransferase and methyltransferase, were screened for their possible involvement in dendrobine biosynthesis. This study provides a good example of endophytes promoting the formation of bioactive compounds in their host and paves the way for further investigation of the dendrobine biosynthetic pathway.
内容测定和微观观察证明，在被共生真菌 MF23（蘑菇属）感染后，铁皮石斛茎中石斛碱的积累增加。共生和非共生铁皮石斛的大规模转录组测序表明，有 30 个可能与石斛碱倍半萜骨架生物合成有关的蛋白质编码基因。随机选择的 16 个基因的 qRT-PCR 实验证明，接种后 9 周时，AACT、MVD、PMK 和 TPS21 的表达水平有显著变化。这些结果表明，MF23 可能通过调节参与甲羟戊酸（MVA）途径的基因表达来刺激石斛碱的生物合成。根据石斛碱生物碱及其倍半萜前体的结构特征，系统地提出了石斛碱的生物发生途径，这表明后修饰酶可能在石斛碱生物合成中起主要作用。因此，筛选了编码后修饰酶的基因，包括细胞色素 P450、氨基转移酶和甲基转移酶，以研究它们是否参与石斛碱的生物合成。本研究为内生菌促进宿主生物活性化合物的形成提供了一个很好的范例，并为进一步研究石斛碱的生物合成途径铺平了道路。
