Heterologous overexpression of Nothapodytes foetida strictosidine synthase enhances levels of anti-cancer compound camptothecin in Ophiorrhiza rugosa
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Nothapodytes foetida, an endangered tree of Indian origin, is a major source of the anti-cancer monoterpenoid indole alkaloid, camptothecin (CPT). Strictosidine synthase (STR) condenses tryptamine and secologanin to form strictosidine, a universal precursor of terpenoid indole alkaloids including CPT. We cloned full-length str cDNA with an open reading frame of 1059 bp from N. foetida (Nfstr) using a homology-based approach. Different tissues of N. foetida from in vitro grown cultures, as well as a mature tree, showed expression of STR, confirming the constitutive nature of the gene. In vitro tissues showed a positive correlation between STR expression and the CPT content, but tissues from wild-type mature plants did not show a similar pattern. Transgenic Ophiorrhiza rugosa plants overexpressing Nfstr showed 1.9-fold higher CPT than non-transformed plants. The results indicated that overexpression of Nfstr in target plants could improve the levels of CPT and may provide an alternative and sustainable source of camptothecin.
We report the full-length sequence and expression analysis of strictosidine synthase cDNA from Nothapodytes foetida (Nfstr). Further, the overexpression of Nfstr in Ophiorrhiza resulted in twofold enhancement in camptothecin levels.
KeywordsCamptothecin Nothapodytes foetida Ophiorrhiza rugosa Strictosidine synthase Terpenoid indole alkaloid pathway
Terpenoid indole alkaloid
Work communicated in the present manuscript is supported by Department of Atomic Energy, Government of India. Authors thank Head, NABTD for his encouragement and support.
SS conceived and designed the study. SS, SNK, and RKS performed the experiments and analyzed the data. SS, SNK, RKS, and DPF contributed inputs, wrote and critically reviewed the manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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