Multigene Phylogeny, Diversity and Antimicrobial Potential of Endophytic Sordariomycetes From Rosa roxburghii

Germination of pecan seeds changes the microbial community

Endophytes are core of the plant-associated microbiome, and seed endophytes are closely related to the plant growth and development. Seed germination is an important part of pecan's life activities, but the composition and changes of microbes during different germination processes have not yet been revealed in pecan seeds. In order to deeply explore the characteristics of endophytes during the germination process of pecan, high-throughput sequencing was performed on seeds at four different germination stages. Findings of present study was found that the diversity and composition of microorganisms were different in different germination stages, and the microbial richness and diversity were highest in the seed endocarp break stage. It was speculated that the change of endophytes in pecan seeds was related to the germination stage. By evaluating the relationship between microbial communities, the core microbiota Cyanobacteria, Proteobacteria and Actinobacteria (bacterial) and Anthophyta and Ascomycota (fungal) core microbiota were identified in germinating pecan seeds. Finally, biomarkers in different germination processes of pecan seeds were identified by LEfSe analysis, among which Proteobacteria, Gamma proteobacteria and, Cyanobacteria and Ascomycota and Sordariomycetes were most abundant. Thus, this study will help to explore the interaction mechanism between pecan seeds and endophytes in different germination processes, and provide materials for the research and development of pecan seed endophytes.

How Deep Can the Endophytic Mycobiome Go? A Case Study on Six Woody Species from the Brazilian Cerrado

Elucidating the complex relationship between plants and endophytic fungi is very important in order to understand the maintenance of biodiversity, equity, stability, and ecosystem functioning. However, knowledge about the diversity of endophytic fungi from species of the native Brazilian Cerrado biome is poorly documented and remains largely unknown. These gaps led us to characterize the diversity of Cerrado endophytic foliar fungi associated with six woody species (Caryocar brasiliense, Dalbergia miscolobium, Leptolobium dasycarpum, Qualea parviflora, Ouratea hexasperma, and Styrax ferrugineus). Additionally, we investigated the influence of host plant identities on the structure of fungal communities. Culture-dependent methods coupled with DNA metabarcoding were employed. Irrespective of the approach, the phylum Ascomycota and the classes Dothideomycetes and Sordariomycetes were dominant. Using the cultivation-dependent method, 114 isolates were recovered from all the host species and classified into more than 20 genera and 50 species. Over 50 of the isolates belonged to the genus Diaporthe, and were distributed into more than 20 species. Metabarcoding revealed the phyla Chytridiomycota, Glomeromycota, Monoblepharomycota, Mortierellomycota, Olpidiomycota, Rozellomycota, and Zoopagomycota. These groups are reported for the first time as components of the endophytic mycobiome of Cerrado plant species. In total, 400 genera were found in all host species. A unique leaf endophytic mycobiome was identified in each host species, which differed not only by the distribution of fungal species, but also by the abundance of shared species. These findings highlight the importance of the Brazilian Cerrado as a reservoir of microbial species, and emphasize how endophytic fungal communities are diversified and adapted.

First Report of White Leaf Spot Caused by Hypomontagnella monticulosa on Pachira glabra in China

Pachira glabra Pasq. is an ornamental tree widely distributed in tropical and subtropical regions of China. In August 2021, an unknown leaf spot was observed on P. glabra in Xiangtan County, Hunan, China (27.976°N, 113.041°E). Over 1,200 plants were evaluated, and up to 20% of the plants were diseased. In moderately diseased plants, approximately one third of leaves had symptoms with the disease severity estimated to be 31.6 ± 9.4% (n=100). The symptoms first appeared as pale yellow to yellow small dots often confined between leaf veins. These dots gradually enlarged, and coalesced into large pale or white spots with brown borders and yellow halo. In severe infections, early leaf death and defoliation occurred. Thirty lesions (2 × 2 mm) collected from ten trees were sterilized in 75% ethanol for 15 s, 5% sodium hypochlorite for 15 s, rinsed in sterile water three times, placed on oatmeal agar medium (OA) plate with lactic acid (3 ml/liter), and incubated at 28°C for 15 days. After incubation, five isolates with a similar morphology were obtained by single-spore culture. Colonies on OA were white and then turned pale grey. Pigments on the reverse side were pale brown. Conidiophores were hyaline, smooth to finely roughened, usually with virgariella-like branching patterns. Conidiogenouscells were hyaline, smooth, and measured 13.9 to 53.8 long and 1.5 to 2.3 µm wide (average 30.8 × 2.0, n=50). Conidia were single-celled, transparent, smooth, ellipsoid to obovoid, 2.3 to 4.6 × 1.7 to 3.1 µm (average 3.1 × 2.3, n=100) in measurement. For further molecular identification, internal transcribed spacer (ITS), β-tubulin (TUB2), RNA polymerase II (RPB2), and large ribosomal subunit (LSU) genes of a representative isolate TT422 were amplified from genomic DNA, using primers ITS1/ITS4 (Mills et al. 1992), T1/T22 (O'Donnell et al. 1997), RPB2-5F/7cR (Liu et al. 2000), and LROR/LR7 (Rehner et al. 1994), respectively. Sequences of ITS (accession no. OM070368), TUB2 (OM201746), LSU (OM070369), and RPB2 (OM141478) from the isolate TT422 showed >98% identity where sequences overlapped to the reference strain of Hypomontagnella monticulosa MUCL 54604 (KY610404, KX271273, KY624305, and KY610487). Concatenated sequences were used for a phylogenetic analysis based on Maximum Likelihood using MEGA7. Based on morphological and molecular data, the isolate TT422 was identified as H. monticulosa (Ju & Rogers 1995; Lambert et al. 2019). Pathogenicity tests were performed three times on healthy leaves using the isolate TT422. Three leaves on one-year-old plants were slightly wounded by a sterile needle, and sprayed with conidial suspension (1×106 conidia/ml, containing 0.05% Tween 20) . Control leaves were sprayed with sterile water containing 0.05% Tween 20. All plants were kept in a greenhouse for 24 h at 28°C and 80% relative humidity, with a 16-h photoperiod and then transferred to natural conditions. All inoculated leaves developed white leaf spot symptoms after 7 days similar to those observed in the field, whereas no visible symptoms appeared on the control leaves. H. monticulosa strains were reisolated from all symptomatic leaves, fulfilling Koch's postulates. H. monticulosa isolated from marine or endophytic origin has been reported to produce bioactive metabolites with anticancer and microbial activities (Leman-Loubière et al. 2017; Lutfia et al. 2021; Zhang et al. 2021), but not as a phytopathogen. To our knowledge, this is the first report of H. monticulosa causing white leaf spot on P. glabra in China and worldwide.

Neuroprotection of Kaji-Ichigoside F1 via the BDNF/Akt/mTOR Signaling Pathways against NMDA-Induced Neurotoxicity

Kaji-ichigoside F1 (KF1), a natural oleanane-type triterpenoid saponin, is the main active constituent from Rosa roxburghii. In the southwest regions of China, particularly in Guizhou Province, this plant was used as a Miao ethnic medicine to prevent and treat dyspepsia, dysentery, hypoimmunity, and neurasthenia. In the present study, the neuroprotective effect of KF1 was evaluated against N-methyl-D-aspartate (NMDA)-induced neurotoxicity in vivo and in vitro. An NMDA-induced PC12 cell neurotoxicity assay showed that KF1 effectively improved cellular viability, inhibited the release of lactate dehydrogenase (LDH), and reduced cell apoptosis. Furthermore, KF1-treated NMDA-induced excitotoxicity mice displayed a remarkable capacity for improving spatial learning memory in the Y-maze and Morris water maze tests. In addition, KF1 increased the levels of the neurotransmitters 5-hydroxytryptamine, dopamine, and monoamine oxidase and reduced the calcium ion concentration in the hippocampus of mice. Hematoxylin and eosin and Nissl staining indicated that KF1 effectively reduced the impairment of neurons. Furthermore, Western blot assays showed that KF1 decreased NMDAR1 expression. In contrast, the NMDAR2B (NR2B), glutamate receptor (AMPA), TrkB, protein kinase B (AKT), mammalian target of rapamycin (mTOR), PSD95, and synapsin 1 were upregulated in NMDA-induced PC12 cells and an animal model. These results suggest that KF1 has a remarkable protective effect against NMDA-induced neurotoxicity, which is directly related to the regulation of the NMDA receptor and the activation of the α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor (AMPAR) and BDNF/AKT/mTOR signaling pathways.

Screening for broad-spectrum antimicrobial endophytes from Rosa roxburghii and multi-omic analyses of biosynthetic capacity

Plants with certain medicinal values are a good source for isolating function-specific endophytes. Rosa roxburghii Tratt. has been reported to be a botanical source of antimicrobial compounds, which may represent a promising candidate for screening endophytic fungi with antimicrobial potential. In this study, 54 endophytes were isolated and molecularly identified from R. roxburghii. The preliminary screening using the plate confrontation method resulted in 15 different endophytic strains showing at least one strong inhibition or three or more moderate inhibition against the 12 tested strains. Further re-screening experiments based on the disc diffusion method demonstrated that Epicoccum latusicollum HGUP191049 and Setophoma terrestris HGUP190028 had excellent antagonistic activity. The minimum inhibitory concentration (MIC) test for extracellular metabolites finally indicated that HGUP191049 had lower MIC values and a broader antimicrobial spectrum, compared to HGUP190028. Genomic, non-target metabolomic, and comparative genomic studies were performed to understand the biosynthetic capacity of the screened-out endophytic fungus. Genome sequencing and annotation of HGUP191049 revealed a size of 33.24 megabase pairs (Mbp), with 24 biosynthetic gene clusters (BGCs), where the putative antimicrobial compounds, oxyjavanicin, patulin and squalestatin S1 were encoded by three different BGCs, respectively. In addition, the non-targeted metabolic results demonstrated that the strain contained approximately 120 antimicrobial secondary metabolites and was structurally diverse. Finally, comparative genomics revealed differences in pathogenicity, virulence, and carbohydrate-active enzymes in the genome of Epicoccum spp. Moreover, the results of the comparative analyses presumed that Epicoccum is a promising source of antimicrobial terpenes, while oxyjavanicin and squalestatin S1 are antimicrobial compounds shared by the genus. In conclusion, R. roxburghii and the endophytic HGUP191049 isolated from it are promising sources of broad-spectrum antimicrobial agents.

Insights into taxonomic diversity and bioprospecting potential of Cerrado endophytic fungi: a review exploring an unique Brazilian biome and methodological limitations

Cerrado is the second largest biome in Brazil, and it is known for harboring a wide variety of endemic plant and microbial species, among which are endophytic fungi. Endophytic fungi are microorganisms capable of colonizing the interior of plant tissues without causing disease in host plants. Especially in the Cerrado biome, this group of microorganisms is still poorly studied and information on species estimation, ecological and evolutionary importance is not accurate and remains unknown. Also, it is extremely important to emphasize that great part of studies available on Cerrado endophytic fungi are national literature, including master's dissertations, course conclusion works or unpublished doctoral theses. The majority of these studies has highlighted that the endemic plant species are an important habitat for fungal endophytes, and new species have increasingly been described. Due to the lack of international literature on Cerrado endophytic fungi, the present review brings a bibliographic survey on taxonomic diversity and bioprospecting potential of fungal endophytes from a unique environment. This review also emphasizes the importance of studying Brazilian endophytic fungi from Cerrado as a source of new technologies (biofertilizer and biocontroller), since they are secondary metabolite-producing organisms with different biological activities for biotechnological, agricultural and pharmaceutical applications.