Molecular cloning and functional characterization of multiple geranylgeranyl pyrophosphate synthases (ApGGPPS) from Andrographis paniculata.

KEY MESSAGE: We found that ApGGPPS1, ApGGPPS2, and ApGGPPS3 can convert IPP and DMAPP to GGPP. ApGGPPS2 is probably involved in andrographolide biosynthesis. ApGGPPS3 may be responsible for the synthesis of the cytosolic GGPP. Andrographis paniculata is a traditional herb for the treatment of sore throat, flu, upper respiratory tract infections and other disorders. In A. paniculata, GGPP is not only the precursor of andrographolide and its primary bioactive compounds, but also the precursor of chlorophylls, carotenoids, gibberellins, and abscisic acid, which are the biomolecules of photosynthesis, growth regulation and other physiological and ecological processes. In this study, four cDNAs (named ApGGPPS1, ApGGPPS2, ApGGPPS3 and ApGGPPS4) encoding geranylgeranyl pyrophosphate synthases from A. paniculata were putatively isolated. Bioinformatic and phylogenetic analyses suggested that these ApGGPPS are highly similar to the geranylgeranyl pyrophosphate synthases in other plants. Prokaryotic expression showed that ApGGPPS1, ApGGPPS2 and ApGGPPS3 could convert IPP and DMAPP to GGPP, although ApGGPPS4 lacks a similar function. The expression of ApGGPPS2 was similar as ApCPS2 under MeJA treatment, ApCPS2 involved in the biosynthesis pathway of andrographolide (Shen et al., Biotechnol Lett 38:131-137, 2016a), has been proven through Virus-induced Gene Siliencing (VIGS) (Shen et al., Acta Bot Boreal 36:17-22, 2016b), and the subcellular localization of ApGGPPS2 was shown to localize in the plastid, suggested that ApGGPPS2 could be the key synthase in the biosynthesis pathway of andrographolide. In addition, ApGGPPS3 was shown to localize in the cytoplasm, suggested that ApGGPPS3 may be responsible for the synthesis of cytosolic GGPP, which may participate in the synthesis of cytosolic oligoprenols as side chains to produce ubiquinone, dolichols or other isoprenoids, in the synthesis of polyisoprenoids, and in protein prenylation.