Diversity and Geographic Distribution of Ligninolytic Fungi Associated With Castanopsis sieboldii Leaf Litter in Japan

The diversity and geographic pattern of ligninolytic fungi were investigated within the distribution range of an evergreen tree, Castanopsis sieboldii (Fagaceae), in Japan. Fungal isolates obtained from 18 sites in subtropical and temperate regions in Japan were classified into 50 operational taxonomic units in Ascomycota and Basidiomycota according to the base sequence of the rDNA internal transcribed spacer region. Ordination by nonmetric multidimensional scaling showed the separation of fungal compositions between the study sites which was significantly related to the latitude, longitude, and mean annual temperature (MAT) of the study sites. We applied variation partitioning to separate the magnitude of the climatic, spatial, and leaf property factors and found the roles of MAT and spatial factors in structuring fungal assemblages, suggesting the importance of both niche processes and such non-niche processes as priority effect and dispersal limitation. The bleached area on leaf litter was greater at sites with higher MAT and precipitation located at lower latitudes and at sites where some major ligninolytic fungi occurred at greater relative frequencies, indicating that not only the climatic conditions but also the biogeographic patterns of distribution of ligninolytic fungi influence the decomposition of lignin in leaf litter.

Visualization and Localization of Submicron-Sized Ammonium Sulfate Particles on Needles of Japanese Larch (Larix kaempferi) and Japanese Cedar (Cryptomeria japonica) and Leaves of Japanese Beech (Fagus crenata) and Japanese Chinquapin (Castanopsis sieboldii) after Artificial Exposure

We applied a method combining field-emission scanning electron microscopy (FE-SEM) with energy dispersive X-ray spectrometry (EDX) to visualize the deposition and localization of the submicron-sized ammonium sulfate (AS) particles. The AS particles emitted from an aerosol generator in the laboratory were spherical in shape and individually deposited without aggregation on the surface of a silicon substrate. We determined the AS particles on the surfaces of the needles of Japanese larch (Larix kaempferi) and Japanese cedar (Cryptomeria japonica), and the leaves of Japanese beech (Fagus crenata) and Japanese chinquapin (Castanopsis sieboldii), using EDX. The particles were deposited on either the adaxial or abaxial side of the leaves and needles. The AS particles deposited on the surfaces of the leaves and needles did not aggregate, and they were deposited on the surfaces of the leaves and needles in the same manner, regardless of leaf structure. These results, using a new method, highlight the early stages of the deposition and localization of submicron-sized AS particles on the surfaces of the leaves and needles of forest trees.

Reductive Metabolism of Ellagitannins in the Young Leaves of Castanopsis sieboldii

The leaves of Castanopsis sieboldii (Fagaceae) contain characteristic hexahydroxydiphenoyl (HHDP) esters of 28-O-glucosyl 2α,3β,23,24-tetrahydroxyolean- and urs-12-en-28-oic acids. In this study, uncharacterized substances were detected in the young leaves, which are not observed in the mature leaves. Preliminary HPLC analyses indicated that the substances had dehydro-HHDP (DHHDP) ester groups; however, the esters were unstable and decomposed during extraction. Therefore, the compounds were isolated as their stable phenazine derivatives by extracting the young leaves with acidic aqueous EtOH containing o-phenylenediamine. The structures of the phenazine derivatives indicated that the unstable metabolites of the young leaves were 3,24-DHHDP esters of the abovementioned triterpenes. Extraction of the young leaves with 80% acetonitrile containing reducing agents, ascorbic acid or dithiothreitol afforded the corresponding HHDP esters. Furthermore, heating of the young leaves in 80% acetonitrile also yielded the same HHDP esters as the reduction products. The results suggested that the HHDP esters are reductively produced from DHHDP esters in the young leaves. In addition, the structures of five previously reported triterpene HHDP esters were revised.

Biogeographic patterns of ectomycorrhizal fungal communities associated with Castanopsis sieboldii across the Japanese archipelago

Biogeographic patterns in ectomycorrhizal (ECM) fungal communities and their drivers have been elucidated, including effects of host tree species and abiotic (climatic and edaphic) conditions. At these geographic scales, genotypic diversity and composition of single host tree species change with spatial and environmental gradients, reflecting their historical dispersal events. However, whether the host genotypes can be associated with the biogeographic patterns of ECM communities remains unclear. We investigated the biogeographic pattern of ECM fungal community associated with the single host species Castanopsis sieboldii (Fagaceae), whose genotypic diversity and composition across the Japanese archipelago has already been evaluated, and we quantified the effect of host genotypes on the biogeographic pattern. Richness and community composition of ECM fungi changed with latitude and longitude; these biogeographic changes of ECM community were significantly explained by host genotypic variables. Quantitative analyses showed a higher relative explanatory power of climatic and spatial variables than that of host genotypic variables for the biogeographic patterns in the ECM community. Our results suggest the importance of historical events of host dispersal in determining the biogeographic patterns of the ECM fungal community, while their explanation power was lower than that for climatic filtering and/or fungal dispersal.