Cloning of a cDNA probably encoding oxidosqualene cyclase associated with asiaticoside biosynthesis from Centella asiatica (L.) Urban

Abstract

A homology-based PCR method was used to clone a cDNA encoding oxidosqualene cyclase from Centella asiatica, which produces a large quantity of triterpene saponins such as asiaticoside and madecassoside. Sequence analysis of one clone found sequences related to beta-amyrin synthase. An open reading frame in the full-length clone was named CabAS (Centella asiatica putative beta-amyrin synthase). On the basis of amino acid sequence, CabAS appears to be an enzyme (beta-amyrin synthase) that synthesizes beta-amyrin. Southern analysis showed that the C. asiatica genome contains one copy of the CabAS gene. Northern blot analysis demonstrated that the CabAS gene is expressed in leaves with no detectable transcript in other plant tissues, consistent with the organ-specific accumulation of the asiaticoside. Up-regulation of expression of CabAS by methyl jasmonate in leaves was also demonstrated.

Characterisation of two phenotypes of Centella asiatica in Southern Africa through the composition of four triterpenoids in callus, cell suspensions and leaves

“…In contrast to our data, they could not detect asiaticoside in undifferentiated cells. Their results have shown that asiaticoside biosynthesis is concentrated in the leaves (0.4-1.4% dry weight) and that the level of asiaticoside content is quite low in the roots of whole plants (Kim et al 2002a(Kim et al , 2004(Kim et al , 2005(Kim et al , 2007.…”

Molecular characterization of ginseng farnesyl diphosphate synthase gene and its up-regulation by methyl jasmonate

“…The results of several reports show that the gene transcriptions of squalene synthase, as well as squalene epoxidase and β-amyrin synthase associated with triterpene biosynthesis, are increased as a consequence of MJ treatment (Suzuki et al 2002, Hayashi et al 2003, Kim et al 2005. Lee et al (2004) demonstrated that PgSS transcription was observed at its highest levels in the adventitious roots of ginseng 24 h after MJ treatment.…”

Molecular characterization and differential expression studies of an oxidosqualene cyclase (OSC) gene of Brahmi (Bacopa monniera)

“…In contrast, the expression level was highest in flower, and roots and hypocotyls in case of Nigella sativa (Scholz et al 2009) and Glycyrrhiza glabra (Hayashi et al 2001) respectively. In other reports, the accumulation of transcripts was higher in leaves of Gentiana straminea (Liu et al 2009) and C. asiatica (Kim et al 2005). …”