Four undescribed polyketides, beshanzones A (1) and B (2) as well as beshanhexanols A (3) and B (4), along with three known ones (5-7) were isolated from the rice fermentation of two endophytic fungi associated with the critically endangered Chinese endemic conifer Abies beshanzuensis. γ-Butyrolactone derivatives 1, 2, and 5 were isolated from Phomopsis sp. BSZ-AZ-2, an interesting strain that drawn our attention this time. The cyclohexanol derivatives 3, 4, 6, and 7 were obtained during a follow-up investigation on Penicillium commune BSZ-P-4-1. The chemical structures including absolute configurations of compounds 1-4 were determined by spectroscopic methods, Mo2(OAc)4 induced electronic circular dichroism (IECD), GIAO NMR calculations and DP4+ probability analyses. In particular, compound 2 contains a novel 5/5 bicyclic ring system, which might be biogenetically derived from the known compound 5 through hydrolysis followed by an Aldol reaction. All isolates were evaluated for their antimicrobial activities against a small panel of bacterial and fungal pathogens. Compounds 6 and 7 showed moderate inhibitory activities against Candida albicans, with MIC values of 16 and 32 μg/mL, respectively.

Root hair is regarded as a pivotal complementary survival tactic for mycorrhizal plant like Abies beshanzuensis when symbiosis is disrupted. Relatively little is known about the mechanism underlying root hair morphogenesis in plant species that are strongly dependent on mycorrhizal symbiosis. Many of these species are endangered, and this knowledge is critical for ensuring their survival. Here, a MYB6/bHLH13-sucrose synthase 2 (AbSUS2) module was newly identified and characterized in A. beshanzuensis using bioinformatics, histochemistry, molecular biology, and transgenesis. Functional, expression pattern, and localization analysis showed that AbSUS2 participated in sucrose synthesis and was involved in root hair initiation in A. beshanzuensis. Additionally, the major enzymatic product of AbSUS2 was found to suppress root hair initiation in vitro. Our data further showed that a complex involving the transcription factors AbMYB6 and AbbHLH13 directly interacted with the promoter of AbSUS2 and strengthened its expression, thereby inhibiting root hair initiation in response to exogenous sucrose. Our findings offer novel insights into how root hair morphogenesis is regulated in mycorrhizal plants and also provide a new strategy for the preservation of endangered mycorrhizal plant species.

Abies beshanzuensis, an extremely rare and critically endangered plant with only three wild adult trees globally, is strongly mycorrhizal-dependent, leading to difficulties in protection and artificial breeding without symbiosis. Root hair morphogenesis plays an important role in the survival of mycorrhizal symbionts. Due to the lack of an effective genome and transcriptome of A. beshanzuensis, the molecular signals involved in the root hair development remain unknown, which hinders its endangered mechanism analysis and protection. Herein, transcriptomes of radicles with root hair (RH1) and without root hair (RH0) from A. beshanzuensis in vitro plantlets were primarily established. Functional annotation and differentially expressed gene (DEG) analysis showed that the two phenotypes have highly differentially expressed gene clusters. Transcriptome divergence identified hormone and sugar signaling primarily involved in root hair morphogenesis of A. beshanzuensis. Weighted correlation network analysis (WGCNA) coupled with quantitative real-time PCR (qRT-PCR) found that two hormone-sucrose-root hair modules were linked by IAA17, and SUS was positioned in the center of the regulation network, co-expressed with SRK2E in hormone transduction and key genes related to root hair morphogenesis. Our results contribute to better understanding of the molecular mechanisms of root hair development and offer new insights into deciphering the survival mechanism of A. beshanzuensis and other endangered species, utilizing root hair as a compensatory strategy instead of poor mycorrhizal growth.

Two unprecedented ent-18,19-dinoricetexane diterpenoid glycosides, named abieshanesides A (1) and B (2), together with seven known compounds, have been isolated from the dead trunks and branches of Abies beshanzuensis M.H. Wu. To our knowledge, abieshanesides A and B represent the first ent-18,19-dinoricetexane diterpenoid glycosides found in natural sources. Their structures and absolute configurations were elucidated by using a combination of spectroscopic techniques and comparison of experimental and calculated electronic circular dichroism (ECD) data. The MTT experiments showed that (E)-resveratrol (7) could inhibit viability of MH7A cells with the IC50 value of 12.5 μM. Compound 7 was able to block MH7A cell proliferation and was associated with G0/G1-phase cell cycle arrest. Flow cytometric analysis showed that the treatment by 7 significantly induced the proliferation of MH7A cells in a dose-dependent manner.

Abies beshanzuensis is critically endangered and endemic to Zhengjiang province of China, with only three surviving individuals. In present study, we reported the complete chloroplast (cp) genome of Abies beshanzuensis. The complete chloroplast genome size is 121,399 bp. In total, 114genes were identified, including 68 peptide-encoding genes, 35 tRNA genes, four rRNA genes, six open reading frames and one pseudogene. Loss of ndh genes was also identified in the genome of A. beshanzuensis like other genomes in the family Pinaceae. Thirteen genes contain one (11 genes) or two (rps12 and ycf3 genes) introns. Inverted repeat sequences located in 42-kb inversion points (1186 bp) include trnS-psaM-ycf12-trnG genes. In phylogenetic analysis, the tree confirms that the four Abies species are strongly supported as monophyletic. The complete plastome of A. beshanzuensis will provide potential genetic resources for further conservation and evolutionary studies of this highly endangered species.

A new N-methoxy-1-pyridone alkaloid [chromenopyridin A (1)] and four known compounds (2-5) were isolated and identified from the endophytic fungus Penicillium nothofagi P-6, which was derived from the bark of the critically endangered conifer Abies beshanzuensis. Their structures were elucidated by extensive spectroscopic analyses and single-crystal X-ray diffraction. Among the isolates, compound 1 showed considerable cytotoxicities against the A549 and Hela human cancer cell lines, with IC50 values of 14.7 and 11.3 μM. In addition, compounds 1 and 4 exhibited potent antibacterial activity against Staphylococcus aureus with MIC values of 62.5 and 15.6 μg/mL, respectively.

Two new [asperxins A (1) and B (2)] and four known (3-6) aflatoxins were isolated and identified from the endophytic fungus Aspergillus sp. Y-2, which was derived from the needles of the critically endangered conifer Abies beshanzuensis. Their structures were elucidated by extensive spectroscopic methods. Among the isolates, compounds 1 and 5 showed considerable cytotoxicities against the A549 and Hela human cancer cell lines, with IC50 values in the range of 7.5-16.8 μM.

During a further and comprehensive phytochemical investigation on the shed trunk barks of the critically endangered plant Abies beshanzuensis, one new (1) and ten known (2-11) lignans with diverse structures were isolated. On the basis of spectroscopic methods, the new structure was established to be (7S,8R,8\'R)-4\'-methoxyl-α-conidendrin (1). Among the isolated lignans, (-)-matairesinol (5) and (-)-arctigenin (6) showed significant anti-neuroinflammatory activities by inhibiting the overproduction of nitric oxide in lipopolysaccharide-stimulated murine BV-2 microglial cells, with IC50 values of 11.5 and 19.0 μM, respectively.