title: Hypericin biosynthesis in Hypericum hookerianum Wight and Arn: investigation on biochemical pathways using metabolite inhibitors and suppression subtractive hybridization.
abstract: The biochemical pathway to hypericin biosynthesis is presumed to be polyketide synthase (PKS) mediated, but it has not been experimentally validated, and no alternate route (chorismate/o-succinylbenzoate pathway) has been analyzed. We report here our earlier developed auxin inducible culture systems of Hypericum hookerianum as a model, to study the metabolic pathway to hypericin synthesis. Inhibitors of the alternate pathway at varying concentrations showed steady synthesis of total hypericins with means of 2.80±0.22, 18.75±0.01; 16.39±3.75, 29.60±1.90 (mevinolin) 2.53±0.10, 18.12±0.56; 0.14±0.01, 14.28±1.11 (fosmidomycin) and 2.7±0.35, 18.75±0.61; 0.14±0.01, 12.80±1.09 mg g(-1) DW (glyphosate) in the control and auxin-induced shoot and shoot-forming callus cultures, respectively. SSH analysis classified the differentially expressed sequences into protein synthesis (38%), modification (20%), electron transport (9%) and remaining as unclassified (11%) and unknown proteins (22%). Functional annotation of sequences indicates the presence of additional protein components besides PKS activity. Our results demonstrate direct biochemical and molecular evidence of PKS hypothesis of hypericin biosynthesis for the first time.
authors.affiliation: Biotechnology and Bioinformatics Division, Jawaharlal Nehru Tropical Botanic Garden and Research Institute, Palode, Thiruvananthapuram 695 562, India. Electronic address: padmeshpad@rediffmail.com.
authors.forename: Padmesh P
authors.initials: PP
authors.lastname: Pillai
authors.affiliation: School of Biotechnology, National Institute of Technology, Calicut 673 601, India.
authors.forename: Aswati R
authors.initials: AR
authors.lastname: Nair
mesh_terms: D000873:Anthracenes; D004642:Emodin / Q000737:chemistry / Q000378:metabolism; D005578:Fosfomycin / Q000008:administration & dosage / Q000031:analogs & derivatives; D005998:Glycine / Q000008:administration & dosage / Q000031:analogs & derivatives; D020902:Hypericum / Q000187:drug effects / Q000378:metabolism*; D007210:Indoleacetic Acids / Q000494:pharmacology; D008148:Lovastatin / Q000008:administration & dosage; D010569:Perylene / Q000031:analogs & derivatives* / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D018520:Plant Shoots / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D048630:Polyketide Synthases / Q000378:metabolism; D046509:Tissue Culture Techniques; D000097797:Glyphosate
chemical_list: D000873:Anthracenes; D004642:Emodin; D005578:Fosfomycin; D005998:Glycine; D007210:Indoleacetic Acids; D008148:Lovastatin; D010569:Perylene; D048630:Polyketide Synthases; D000097797:Glyphosate; C024640:fosmidomycin; C004965:hypericin
keywords: Fosmidomycin; Glyphosate; Hypericin; Hypericum hookerianum; Mevinolin; SSH; Type III PKS