Abstract
Background) Nostoc sp., a cyanobacterium establishes symbiosis with cycad (Cycus revolute) root. Nostoc sp. firstly recognizes the host plant root, next moves to the root tip, and eventually induces the coralloid root. Generally Nostoc sp. does not possess motility, but it differentiates to hormogonia, a motile form. Hypothetically, cycad root releases hormogonia-inducing factor (HIF) to establish the symbiosis between them. In this research, we screened HIF-like principle from the coralloid roots. Materials and Method) The coralloid roots collected at Yaku Island in late March, 2009 (1.08kg), and at Tanegashima Island, in early May, 2010 (6.25kg), were soaked in MeOH. It was concentrated and re-suspended in water (ca. 1000ml) to be extracted with equal volume of EtOAc to give 2.58g of EtOAc solubles. In a paper disc assay, aggregated colonies of Nostoc sp. was impregnated in 0.6% Winogradsky's agar medium, and the fraction-charged paper disc (9mm diameter, 0.25mm thick) were put onto the agar plates and incubated at 25oC. When the aggregated colonies of Nostoc sp. around the paper disc started to be dispersed within 2 days, the fraction was judged to contain HIF. The active fraction was further purified to elucidate structures of HIF. Results and Discussions) After 12-h of incubation, Nostoc sp. around 40% EtOAc fraction started to be dispersed. Under a light microscopic observation, some chain-like cells turned into hormogonia, to acquire motilitiy. Using this bioassay system, pure active principle was obtained 1mg of the colorless syrup from the 1kg fr. wt. of coralloid. In spectroscopic analyses and chemical derivatization using FD-MS, ^1H-NMR and treatment with lipase followed by released fatty acid analyses by FD-MS, it was concluded that the HIF is a 1,2-diacylglycerol possessing linolic acid and palmitic acid as constitutive fatty acids.
