Diterpene cyclases from bacteria and basidiomycete fungi are seldom studied. Here, we presented the identification and verification of EriG, a member of the UbiA superfamily, as the enzyme responsible for the cyclization of the cyathane skeleton in the mushroom Hericium erinaceum. Genome mining using the EriG protein sequence as a probe led to the discovery of a new family of ubiquitous UbiA-related diterpene cyclases in bacteria and fungi. We successfully characterized seven new diterpene cyclases from bacteria or basidiomycete fungi with the help of an engineered Escherichia coli strain and determined the structures of their corresponding products. A new diterpene with an unusual skeleton was generated during this process. The discovery of this new family of diterpene cyclases provides new insight into the UbiA superfamily.

NotesThe traditional Chinese medicine "Shi Hu", prepared from the dried or fresh stems of several Dendrobium species (Orchidaceae), is widely used as both traditional Chinese and folk remedies for antipyretic, eyes-benefiting, and tonic purposes.1) Dendrobium candidum WALL. ex LINDL. is one of the most popular and valuable Dendrobium species and has been recorded in the Chinese Pharmacopoeia (2005 Edition) as one of the original materials of "Shi Hu". However, no phytochemical study of D. candidum has been reported to date. So, a phytochemical investigation on D. candidum has been undertaken by our group. As a result, two new compounds (1, 2) were isolated, along with five known compounds (3-7). [2][3][4][5] The known compounds were identified by comparisons with previously reported physical and spectral data. ) and NMR analysis revealed the molecular formula C 17 H 20 O 5 . The structure of 1 was deduced from its 1D-and 2D-NMR data and comparison with those of 3,4-dihydroxy-5,4Ј-dimethoxybibenzyl (4).3) The absolute configuration of 1 was established as (R) on the basis of the negative Cotton effect at 230 nm (De Ϫ1.29) in its circular dichroism (CD) spectrum, which was opposite to those of analogs (notice that the stereodescriptor is (S) in those cases). C-NMR data, a bibenzyl skeleton with two hydroxyl and three methoxyl groups were deduced to the structure of 1. But the significant difference between 1 and the 3,4-dihydroxy-5,4Ј-dimethoxybibenzyl (4) reported 3) was observed at benzylic protons. The four equivalent benzylic proton signals in upfield region of the known bibenzyl were replaced by the signals for one oxygenated methine and two methylene protons in 1. In combination with the 13 C-1 H long-range correlation between d H 3.19 (a-OMe-H 3 ) and d C 85.2 (C-a) in the HMBC spectrum, the fragment of one benzylic proton substituted by a methoxyl group was determined. Other key HMBC correlations are shown in Fig. 2. Thus, the structure of 1 was established as (R)-3,4-dihydroxy-5,4Ј,a-trimethoxybibenzyl. Two new compounds were isolated from the stems of Dendrobium candidum: (R)-3,4-dihydroxy-5,4,a atrimethoxybibenzyl (1), named dendrocandin A; and 4-[2-[(2S,3S)-3-(4-hydroxy-3,5-dimethoxyphenyl)-2-hydroxymethyl-8-methoxy-2,3-dihydrobenzo[1,4]dioxin-6-yl]ethyl]-1-methoxyl benzene (2), dendrocandin B. Five previously known bibenzyls were also identified: 4,4-dihydroxy-3,5-dimethoxybibenzyl (3), 3,4-dihydroxy-5,4-dimethoxybibenzyl (4), 3-O-methylgigantol (5), dendrophenol (6), and gigantol (7).

Polyporus umbellatus, a species symbiotic with Armillaria mellea and it also exhibits substantial defence response to Armillaria mellea infection. There are no genomics resources databases for understanding the molecular mechanism underlying the infection stress of P. umbellatus. Therefore, we performed a large-scale transcriptome sequencing of this fungus with A. mellea infection using Illumina sequencing technology. The assembly of the clean reads resulted in 120,576 transcripts, including 38,444 unigenes. Additionally, we performed a gene expression profiling analysis upon infection treatment. The results indicated significant differences in the gene expression profiles between the control and the infection group. In total, 10933 genes were identified between the two groups. Based on the differentially expressed genes, a Gene Ontology annotation analysis showed many defence-relevant categories. Meanwhile, the Kyoto Encyclopedia of Genes and Genomes pathway analysis uncovered some important pathways. Furthermore, the expression patterns of 13 putative genes that are involved in defence response resulting from quantitative real-time PCR were consistent with their transcript abundance changes as identified by RNA-seq. The sequenced genes covered a considerable proportion of the P. umbellatus transcriptome, and the expression results may be useful to strengthen the knowledge on the defence response of this fungus defend against Armillaria mellea invasion.

Dendrobium candidum (Orchidaceae) is one of the original materials of "Shi Hu", used as both traditional Chinese and folk remedies for antipyretic, eyes-benefiting, and tonic purposes. 1) In the previous study, we have reported the isolation of seven compounds from D. candidum.2) Our continuing research on the phytochemical constituents of D. candidum, led to the isolation of three new bibenzyl derivatives (1-3). Because of the reported antioxidant activity of some bibenzyl derivates, 3) we evaluated the antioxidant activity of compounds 1-3 by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging test. The present paper deals with the structure elucidation and the antioxidant evaluation of compounds 1-3.Dendrocandin C (1) C-NMR data of 1 were similar to those of dendrocandin A, 2) except for the disappearance of a methoxyl group at C-4Ј of dendrocandin A. According to the 1D-and 2D-NMR data and the molecular formula of compound 1 showed that a hydroxyl group substituted at C-4Ј of 1. The key heteronuclear multiple bond correlation (HMBC) correlations are shown in Fig. 2. The absolute configuration of 1 was established as (S) on the basis of the positive Cotton effect at 226 nm (De ϩ2.64) in its circular dichroism (CD) spectrum, which was opposite to those of dendrocandin A.2) Based on the above evidence, the structure of 1 was deduced to be (S)-3,4,4Ј-trihydroxy-5,adimethoxybibenzyl, named dendrocandin C. C-NMR data of 2 were similar to those of compound 1, except for an additional ethoxyl signal and the disappearance of a methoxyl group at C-a of 1. The additional ethoxyl group located at C-a, which was confirmed by Three new compounds were isolated from the stems of Dendrobium candidum: (S)-3,4,4-trihydroxy-5,a adimethoxybibenzyl (1), named dendrocandin C; (S)-3,4,4-trihydroxy-5-methoxy-a a-ethoxybibenzyl (2), named dendrocandin D; and 3,3,4,4-tetrahydroxy-5-methoxybibenzyl (3), named dendrocandin E. Their structures were elucidated by 1D-and 2D-NMR spectroscopy and mass spectroscopy. The isolated compounds exhibited potent antioxidant activity in the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging test, with IC 50 values of 34.2, 34.5, and 15.6 m mM for compounds 1, 2, and 3, respectively. Vitamin C was used as positive control with IC 50 23.2 m mM.

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