Kazuhiko Kinjo

Triterpene synthases from the Okinawan mangrove tribe, Rhizophoraceae

Oleanane‐type triterpene is one of the most widespread triterpenes found in plants, together with the lupane type, and these two types often occur together in the same plant. Bruguiera gymnorrhiza (L.) Lamk. and Rhizophora stylosa Griff. (Rhizophoraceae) are known to produce both types of triterpenes. Four oxidosqualene cyclase cDNAs were cloned from the leaves of B. gymnorrhiza and R. stylosa by a homology‐based PCR method. The ORFs of full‐length clones termed BgbAS (2280 bp, coding for 759 amino acids), BgLUS (2286 bp, coding for 761 amino acids), RsM1 (2280 bp, coding for 759 amino acids) and RsM2 (2316 bp coding for 771 amino acids) were ligated into yeast expression plasmid pYES2 under the control of the GAL1 promoter. Expression of BgbAS and BgLUS in GIL77 resulted in the production of β‐amyrin and lupeol, suggesting that these genes encode β‐amyrin and lupeol synthase (LUS), respectively. Furthermore, RsM1 produced germanicol, β‐amyrin, and lupeol in the ratio of 63 : 33 : 4, whereas RsM2 produced taraxerol, β‐amyrin, and lupeol in the proportions 70 : 17 : 13. This result indicates that these are multifunctional triterpene synthases. Phylogenetic analysis and sequence comparisons revealed that BgbAS and RsM1 demonstrated high similarities (78–93%) to β‐amyrin synthases, and were located in the same branch as β‐amyrin synthase. BgLUS formed a new branch for lupeol synthase that was closely related to the β‐amyrin synthase cluster, whereas RsM2 was found in the first branch of the multifunctional triterpene synthase evolved from lupeol to β‐amyrin synthase. Based on these sequence comparisons and product profiles, we discuss the molecular evolution of triterpene synthases and the involvement of these genes in the formation of terpenoids in mangrove leaves.

Minor daphnane-type diterpenoids from Wikstroemia retusa

In addition to huratoxin, pimelea factor P2, and wikstroelides A-G from the fresh bark, eight daphnane-type diterpenoids, wikstroelides H-O, were isolated from the bark and stem, and their structures established. Cytotoxicity was assayed on some wikstroelides.

Daphnane diterpenoids from the bark of Wikstroemia retusa

On examination of the less polar fraction from the bark of Wikstroemia retusa, nine daphnane-type diterpenoids, including four known ones, were isolated and the structures established.

Corticioid fungi (Basidiomycota) in mangrove forests of the islands of Iriomote and Okinawa, Japan

Sixteen species of corticioid fungi (Basidiomycota) were collected from mangrove forests in the islands of Iriomote and Okinawa, Japan. All the species are new records for the Japanese mangrove forests. Of these species, 6 species are newly reported from Japan: Cerocorticium molle, Gloeocystidiellum moniliforme, G. wakullum, Hyphoderma ayresii, Phanerochaete tropica, and Phlebia acanthocystis. Their morphological descriptions, illustrations, and remarks based on the Japanese specimens are provided.

Wood decaying properties of the termite mushroom Termitomyces eurrhizus

Four strains of the termite mushroom Termitomyces eurrhizus collected in Japan were surveyed for their wood decaying properties in three softwood and two hardwood species, in comparison with the white-rot fungus Trametes versicolor and the brown-rot fungus Fomitopsis palustris. All strains of T. eurrhizus degraded only the surfaces of the wood samples, and differences in mass-loss rates between heartwood and sapwood were generally not significant. Higher mass-loss rates were generally obtained in softwood than in hardwood. The results of chemical analyses of decayed wood samples indicated that T. eurrhizus does not have high lignin-degradation ability, even though it is categorized as a white-rot fungus. These results clearly suggest the unique physiological characteristics of T. eurrhizus.

Screening of Strains and Media of Termitomyces eurrhizus Collected from Japan Toward Nutritional Analyses

Twenty-seven strains of Termitomyces eurrhizus, all from Okinawa Prefecture, Japan, were served for screening with eight artificial media. Four strains were selected for their growth, media specificity, and handling for future experiments on nutritional analyses. In addition, the matsutake medium was found to have a good affinity to these strains.