Light modulates glucose metabolism by a retina-hypothalamus-brown adipose tissue axis.

Public health studies indicate that artificial light is a high-risk factor for metabolic disorders. However, the neural mechanism underlying metabolic modulation by light remains elusive. Here, we found that light can acutely decrease glucose tolerance (GT) in mice by activation of intrinsically photosensitive retinal ganglion cells (ipRGCs) innervating the hypothalamic supraoptic nucleus (SON). Vasopressin neurons in the SON project to the paraventricular nucleus, then to the GABAergic neurons in the solitary tract nucleus, and eventually to brown adipose tissue (BAT). Light activation of this neural circuit directly blocks adaptive thermogenesis in BAT, thereby decreasing GT. In humans, light also modulates GT at the temperature where BAT is active. Thus, our work unveils a retina-SON-BAT axis that mediates the effect of light on glucose metabolism, which may explain the connection between artificial light and metabolic dysregulation, suggesting a potential prevention and treatment strategy for managing glucose metabolic disorders.

Melanopsin retinal ganglion cells mediate light-promoted brain development.

During development, melanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGCs) become light sensitive much earlier than rods and cones. IpRGCs project to many subcortical areas, whereas physiological functions of these projections are yet to be fully elucidated. Here, we found that ipRGC-mediated light sensation promotes synaptogenesis of pyramidal neurons in various cortices and the hippocampus. This phenomenon depends on activation of ipRGCs and is mediated by the release of oxytocin from the supraoptic nucleus (SON) and the paraventricular nucleus (PVN) into cerebral-spinal fluid. We further characterized a direct connection between ipRGCs and oxytocin neurons in the SON and mutual projections between oxytocin neurons in the SON and PVN. Moreover, we showed that the lack of ipRGC-mediated, light-promoted early cortical synaptogenesis compromised learning ability in adult mice. Our results highlight the importance of light sensation early in life on the development of learning ability and therefore call attention to suitable light environment for infant care.

First Report of Powdery Mildew on Sophora flavescens Caused by Erysiphe diffusa in China.

Sophora flavescens (Fabaceae) is a deciduous subshrub which has been used in Chinese popular medicine for a long history (He et al. 2015). In June 2023, severe powdery mildew symptoms were observed on wild S. flavescens plants on Longwen hill of Guizhou Normal University, Guiyang, China. The incidence was approximately 80% among 100 S. flavescens plants observed. Almost all leaves were infected. Mycelia occurred on both adaxial and abaxial leaf surfaces, petioles, and stems, forming small-to-large patches. Hyphae were hyaline, 5 to 7 µm wide. Hyphal appressoria were solitary. Conidiophores were erect, straight to somewhat flexuous, and 45 to 120 µm long (n = 50). Foot cells were subcylindrical to slightly curved, followed by 2 to 3 shorter cells. Conidia formed singly, were ovoid to cylindrical, 26 to 42 × 12 to18 µm (n = 50). Based on these morphological characteristics, the powdery mildew fungus was tentatively identified as Erysiphe diffusa (Braun and Cook 2012). To confirm the identification, the ribosomal DNA internal transcribed spacer (ITS) and the ribosomal large subunit (LSU) region were amplified and sequenced using primer pairs ITS1/ITS4 (White et al. 1990) and NL1/NL4 (Ziemiecki et al. 1990), respectively. The obtained 647-bp ITS sequence (GenBank accession no. PP130131) displayed 100% identity with the ITS sequences of E. diffusa. The obtained 618-bp LSU sequence (GenBank accession no. PP693303) displayed 100% identity with the ITS sequences of E. diffusa (MT325922 and MT628019) and E. manihoticola (MT106658 and MT106660). Using a phylogenetic tree based on the combined ITS-LSU data, the isolate was grouped in a clade with the E. diffusa strain (GenBank accession no. LC777871). To fulfill Koch's postulates, leaves of three healthy potted S. flavescens plants were inoculated by gently pressing with diseased leaves. Non-inoculated plants were used as controls. All plants were incubated in a greenhouse at 25 ± 2°C, 80% relative humidity. After 15 days, typical powdery mildew symptoms were observed on the inoculated plants, whereas no symptoms were found on the control plants. The reisolated fungus from the inoculated S. flavescens was morphologically identical to that on naturally diseased plants, and the ITS sequence of the reisolated fungus showed 100% identity with PP130131. As the causal fungus of soybean powdery mildew, E. diffusa is known to infect papaya and other legumes, including Lens culinaris and Mimosa caesalpiniifolia (Attanayake et al. 2009; Luz et al. 2019). Particularly, E. diffusa has been previously reported to infect S. flavescens in the United Kingdom (Jones and Baker 2007; Bradshaw et al. 2023), but this is the first report of S. flavescens powdery mildew caused by E. diffusa in China. This work further expands the geographical range of E. diffusa-infected S. flavescens plants.

First Report of Powdery Mildew on Berchemia floribunda Caused by Erysiphe berchemiae in China.

The genus Berchemia (family Rhamnaceae), a group of climbing plants, is mainly distributed in Asia, Africa, and South America. Berchemia plants are widely used in traditional medicine in some Asian countries (Inoshiri et al. 1987). For example, in Japan, B. racemosa (synonym B. floribunda) is used for the treatment of gallstones, liver diseases, neuralgia, and stomach cramps, and in China, B. floribunda is used for the treatment of rheumatism and lumbago. In August 2022, typical powdery mildew symptoms were observed on wild B. floribunda plants in Huaxi District, Guiyang, Guizhou Province, China. The incidence was approximately 60% among 100 B. floribunda plants observed outdoors. White colonies almost entirely covered on both adaxial and abaxial surfaces of all leaves on symptomatic plants. Infected leaves appeared curled or chlorotic, infection occasionally leading to defoliation. To describe the pathogen morphologically, fungal samples were collected from two individual B. floribunda plants and microscopically characterized. In these samples, hyphae were flexuous to straight, branched, septate, 3-6 µm wide, with lobed hyphal appressoria. Conidiophores were erect, flexuous to straight, and 50-160 µm long (n = 30). Foot cells were subcylindrical to slightly curved-sinuous at the base, 20-40 µm long (n = 30), followed by 2-3 shorter cells. Conidia formed singly, occasionally 2-3 in a chain. Conidia were ellipsoid to ovoid, 20-42 × 12-18 µm (n = 50), without fibrosin bodies. Chasmothecia were not found. For molecular identification, the ribosomal DNA internal transcribed spacers (ITSs) of the two fungal samples were amplified and sequenced using the ITS1/ITS4 primer pair (White et al. 1990). The obtained 649-bp ITS sequences (GenBank accession nos. OR414364 and OR414365, respectively) shared 100% identity, and they showed 99.52% identity with the ITS sequence (GenBank accession no. LC009934) of Erysiphe berchemiae. Phylogenetic analysis grouped OR414364 and OR414365 in a clade with LC009934. Based on morphological and molecular characteristics, the powdery mildew fungus from B. floribunda was identified as E. berchemiae (Braun and Cook 2012). The voucher specimen (accession no. GZNU-BFEE/0820/2022) were deposited at the School of Life Sciences, Guizhou Normal University. Pathogenicity was assessed by gently pressing naturally diseased leaves of B. floribunda onto leaves of three healthy potted 1-year-old B. floribunda plants. Three non-inoculated healthy plants were used as controls. The plants were incubated in a greenhouse at 25 ± 2°C, 80% relative humidity. Similar powdery mildew symptoms were observed on the inoculated plants 9 days after inoculation, whereas the control plants remained symptomless. The reisolated fungus from inoculated leaves was morphologically identical to that observed on the original diseased leaves, and the ITS sequence of the reisolated fungus shared 100% identity with OR414364 and OR414365, fulfilling Koch's postulates. E. berchemiae has previously been described as a powdery mildew pathogen on B. yunnanensis (Chen et al. 1987) and B. kulingensis (Chen 1993) in China and B. racemosa (synonym B. floribunda) in Japan (Braun and Cook 2012; Takamatsu et al. 2015), but this is the first report of E. berchemiae causing disease of B. floribunda in China. This work suggests that E. berchemiae is an important pathogen of Berchemia plants, at least for some species in the genus Berchemia.

First Report of Powdery Mildew on Quercus fabri and Q. robur Caused by Erysiphe quercicola in China.

Quercus (Fagaceae) is a genus of ecologically and economically important shrub and tree species (Yin et al. 2018). In April 2022, powdery mildew symptoms were observed on Quercus fabri and Quercus robur leaves on Longwen hill, Guizhou Normal University, Guiyang, China. The incidence was 30% (Q. fabri, n = 50) and 20% (Q. robur, n = 30), respectively. Powdery mildew fungi from these two Quercus species shared similar morphological characteristics. Mycelia occurred on adaxial and abaxial leaf surfaces, forming small to large patches; hyphae were hyaline, 3-7 µm wide; hyphal appressoria were lobed to multilobed, solitary; conidiophores were erect, straight, 36-80 µm long (n = 30); foot cells were followed by 1-2 shorter cells; conidia formed singly, obovoid to ellipsoid, 24-38 × 12-27 µm (n = 50), without fibrosin bodies; no chasmothecia were observed. Based on these characteristics, powdery mildew fungi on both Q. fabri and Q. robur were identified as Erysiphe quercicola (Takamatsu et al. 2007). To confirm the identification, ribosomal DNA internal transcribed spacer (ITS) sequences of two fungal samples from Q. fabri and Q. robur were separately amplified and sequenced using primer pair ITS1/ITS4 (White et al. 1990). The obtained ITS sequences (GenBank accession nos. QR414372 and QR414373, respectively) shared 100% identity, and 99.38-99.84% identity with diverse ITS sequences of E. quercicola (Takamatsu et al. 2015). In a phylogenetic tree based on ITS sequences of Erysiphe species (Takamatsu et al. 2007), QR414372 and QR414373 were grouped in a clade with ITS sequences of E. quercicola. To fulfil Koch's postulates, leaves of three healthy potted Q. fabri plants and three healthy potted Q. robur plants were inoculated by gently pressing diseased Q. fabri and Q. robur leaves onto healthy leaves. Non-inoculated healthy Q. fabri and Q. robur plants served as controls. All plants were incubated in a greenhouse at 25 ± 2°C with 80% relative humidity. Typical powdery mildew symptoms were observed on all inoculated plants 15 days after inoculation, whereas no symptoms were observed on control plants. Fungi separately reisolated from inoculated Q. fabri and Q. robur were morphologically identical to those on their originally diseased plants, and ITS sequences of reisolated fungi shared 100% identity with QR414372 and QR414373. E. quercicola has previously been reported to infect Quercus species, including Q. robur in Australia, Q. crispula, Q. phillyraeoides and Q. serrata in Japan, and Q. phillyraeoides in Korea (Lee et al. 2011). In China, Q. fabri and Q. robur may be infected by E. alphitoides and E. hypophylla, respectively (Zheng et al. 1987). To our knowledge, this is the first report of powdery mildew caused by E. quercicola on Q. fabri and Q. robur in China. This work provides a foundation to protect Quercus plants against this fungal pathogen.

First Report of Rust Disease on Alcea rosea caused by Puccinia modiolae in China.

Alcea rosea, belonging to the Alcea genus in the Malvaceae family, originated from China, but it is now grown worldwide. A. rosea has been widely used in traditional Chinese medicine to alleviate constipation, pain, swelling, and sores. In February 2023, typical symptoms of fungal infection were observed on A. rosea at Guizhou Normal University in Guiyang, Guizhou Province, China. The disease incidence was over 90% (n = 100) for the surveyed A. rosea plants, and the disease severity range from 30% to 90%. The initial symptoms of A. rosea rust were the appearance of chlorotic spots on the leaves. Subsequently, numerous reddish to dark-brown erumpent pustules (telia) were observed. Gradually, the entire plant was covered by rust and the center of each lesion turned brown, necrotic, and ruptured over times, eventually causing defoliation. Voucher specimens of infected A. rosea leaves as representative samples have been deposited at Guizhou Normal University (GNU2023LS008). Telia are round in shape, mostly aggregated in mass, with a diameter of 0.28-0.78 mm (0.46 mm, n = 20). They range in color from reddish-brown to dark brown, and are mainly hypophyllous but occasionally formed on the adaxial leaf surface. The teliospores are fusoid with dimensions of 31.3-93.8 × 10.9-21.3 µm (57.5 × 15.1 µm average, n = 50), hyaline or yellowish to light-brown in color, mostly two-celled, with a smooth wall (1.5-3.0 µm) and a thickened apex (3.0-9.0 µm). However, teliospores which are one-, three-, or four-celled with a notch at the apex, are rarely observed. The morphological characteristics of host symptoms and teliospores were similar to those of Puccinia modiolae (Aime and Abbasi 2018; Albu et al. 2019). For phylogenetic analysis, genomic DNA was extracted from the teliospores of infected leaves. To confirm the species-level identification, PCR was performed on the extracted DNA to amplify the ribosomal DNA internal transcribed spacer (ITS) and large subunit (LSU) regions using primer pairs ITS1/ITS4 (Schoch et al. 2012) and NL1/NL4 (Ziemiecki et al. 1990), respectively. The resulting ITS DNA sequence (GenBank accession no. OR607960) showed 100% identity with P. modiolae sequences (OP369291.1), when the query coverage was 100%. The LSU DNA sequence obtained (OR607961.2) shared 99.85% similarity with P. modiolae (MK458702.1). A phylogenetic tree was constructed using MEGA7.0 and the maximum likelihood method based on the ITS and LSU sequences. The fungal isolates collected in this study and several reference sequences of P. modiolae were grouped within a clade that included the isolates reported on A. rosea in Korea (Ryu et al. 2023), with 100% bootstrap support. Pathogenicity testing was conducted by gently pressing spore powder of naturally diseased leaves onto young leaves of three healthy A. rosea plants, with three noninoculated healthy plants serving as controls. The inoculated and noninoculated plants were kept in a growth chamber at the 26°C with a 12 hour light/dark cycle and 80% humidity. After 2 weeks, all inoculated A. rosea plants showed characteristic disease symptoms of rust infection and telia of P. modiolae, while control plants remained symptomless. The pathogen was identical to that observed on the original diseased leaves. The study results indicate that the causal fungus responsible for the disease is P. modiolae, which has been previously reported on Malvaceae plants (Farr and Rossman 2022). To the best of our knowledge, this is the first report of P. modiolae on A. rosea in China. This study will contribute to an increased understanding of the host range of Puccinia modiolae.

Optically Readable Organic Electrochemical Synaptic Transistors for Neuromorphic Photonic Image Processing.

Optically readable organic synaptic devices have great potential in both artificial intelligence and photonic neuromorphic computing. Herein, a novel optically readable organic electrochemical synaptic transistor (OR-OEST) strategy is first proposed. The electrochemical doping mechanism of the device was systematically investigated, and the basic biological synaptic behaviors that can be read by optical means are successfully achieved. Furthermore, the flexible OR-OESTs are capable of electrically switching the transparency of semiconductor channel materials in a nonvolatile manner, and thus the multilevel memory can be achieved through optical readout. Finally, the OR-OESTs are developed for the preprocessing of photonic images, such as contrast enhancement and denoising, and feeding the processed images into an artificial neural network, achieving a recognition rate of over 90%. Overall, this work provides a new strategy for the implementation of photonic neuromorphic systems.

Wafer-Scale Single Crystal Hexagonal Boron Nitride Layers Grown by Submicron-Spacing Vapor Deposition.

The direct growth of wafer-scale single crystal two-dimensional (2D) hexagonal boron nitride (h-BN) layer with a controllable thickness is highly desirable for 2D-material-based device applications. Here, for the first time, a facile submicron-spacing vapor deposition (SSVD) method is reported to achieve 2-inch single crystal h-BN layers with controllable thickness from monolayer to tens of nanometers on the dielectric sapphire substrates using a boron film as the solid source. In the SSVD growth, the boron film is fully covered by the same-sized sapphire substrate with a submicron spacing, leading to an efficient vapor diffusion transport. The epitaxial h-BN layer exhibits extremely high crystalline quality, as demonstrated by both a sharp Raman E2g vibration mode (12 cm-1 ) and a narrow X-ray rocking curve (0.10°). Furthermore, a deep ultraviolet photodetector and a ZrS2 /h-BN heterostructure fabricated from the h-BN layer demonstrate its fascinating properties and potential applications. This facile method to synthesize wafer-scale single crystal h-BN layers with controllable thickness paves the way to future 2D semiconductor-based electronics and optoelectronics.

A flexible quasi-likelihood model for microbiome abundance count data.

In this article, we present a flexible model for microbiome count data. We consider a quasi-likelihood framework, in which we do not make any assumptions on the distribution of the microbiome count except that its variance is an unknown but smooth function of the mean. By comparing our model to the negative binomial generalized linear model (GLM) and Poisson GLM in simulation studies, we show that our flexible quasi-likelihood method yields valid inferential results. Using a real microbiome study, we demonstrate the utility of our method by examining the relationship between adenomas and microbiota. We also provide an R package "fql" for the application of our method.

Discovery of Unusual Sesterterpenoids from Colquhounia coccinea var. mollis and Their Metabolic Implications.

Three unusual sesterterpenoids featuring unprecedented rearranged colquhounane (C25) and tetranorcolquhounane (C21) frameworks, colquhounoids E (1) and F (3) and norcolquhounoid F (2), were isolated from a Lamiaceae medicinal plant Colquhounia coccinea var. mollis. Their structures were elucidated by spectroscopic analysis and quantum chemical calculations. A biomimetic inspired regioselective cyclopropane cleavage was achieved under acidic conditions. The immunosuppressive activities of these new sesterterpenoids were also evaluated.

[Traditional Chinese medicine therapy for rheumatoid arthritis: a review].

Rheumatoid arthritis(RA) is an autoimmune disease that seriously affects the physical and mental health of patients, but its pathogenesis is still unclear. At present, clinical treatment drugs include conventional synthetic disease modifing anti-rheumatic drugs(csDMARDs), nonsteroid anti-inflammtory drugs(NSAIDs), hormones, small molecule targeted drugs, biological agents, etc. These drugs can relieve the clinical symptoms of most patients with RA to a certain extent, but there are still many limitations, such as drug adverse reactions and individual differences in drug efficacy. Therefore, the research on drug treatment targets and the development of low-toxicity drugs helps further improve the precise prevention, diagnosis, and treatment of RA. There is an urgent need for efficient and low-toxic treatments to delay the clinical progress of RA. As a treasure of Chinese culture, traditional Chinese medicine(TCM) is widely used as an alternative therapy in the treatment of various diseases, and has a significant clinical efficacy. TCM therapy(including monomer traditional Chinese medicine, classical compounds, and non-drug therapies) has a significant curative effect on RA. Based on the literature research in recent years, this paper reviewed the clinical and mechanism research of TCM therapy in the treatment of RA, and provided more in-depth thinking for the wide application of TCM therapy in clinical practice.

Sonic hedgehog promotes synovial inflammation and articular damage through p38 mitogen-activated protein kinase signaling in experimental arthritis.

Activated fibroblast-like synoviocytes (FLS) play a pivotal role in synovial inflammation and joint destruction of rheumatoid arthritis (RA). The mechanisms by which sonic hedgehog (SHH) signaling promotes RA FLS-mediated chronic inflammation and tissue damage are not fully understood. The present study aims to determine the role of SHH signaling in the pathogenesis of RA and to explore the potential mechanism(s). We found that the components of SHH signaling were highly expressed in FLS and synovial tissue from patients with RA and in the joint tissue of collagen-induced arthritis (CIA) mice. Overexpression of SHH aggravated the synovial inflammation and joint destruction of CIA and exacerbated cartilage degradation in the cartilage and RA FLS-engrafted severe combined immunodeficiency (SCID) model. Conversely, inhibition of SHH signaling significantly alleviated arthritis severity and reduced cartilage destruction caused by the invasion of RA FLS in vivo. Moreover, we found that p38 mitogen-activated protein kinase (MAPK) cascade was regulated by SHH signaling in RA FLS and the level of phospho-p38 in the joint tissue of CIA was decreased after blockade of SHH signaling. Inhibition of p38 MAPK abolished the effect of SHH overexpression on synovial inflammation and articular destruction of CIA and suppressed the aggressive properties of RA FLS, which were promoted by SHH agonist. In conclusion, our study suggests that SHH signaling aggravates synovial inflammation and joint destruction of experimental arthritis and promotes the abnormal behavior of RA FLS in a p38-dependent manner. SHH-p38 MAPK signaling could be a potential target for the treatment of RA.

First Report of Powdery Mildew on Rosa cymosa Caused by Podosphaera pannosa in Guizhou Province, China.

Rosa cymosa is a traditional Chinese medicine and an ornamental plant in China (Fan et al. 2020). In April 2022, powdery mildew symptoms were observed on R. cymosa in Guiyang, Guizhou Province, China. The incidence was approximately 5% among all observed one hundred R. cymosa plants. On average, 20% of the twig tips per diseased R. cymosa plant were affected. Powdery mildew colonies covered the adaxial and abaxial surfaces of leaves. Infected young leaves rolled up along the main vein. Stems and mature leaves occasionally had signs of powdery mildew. The hyphae were straight to flexuous, branched, septate, 3 to 6 µm in width. Conidiophores were erect, straight or somewhat flexuous, and 100 to 235 µm long. Foot cells (n = 30) were cylindrical or subcylindrical, straight or somewhat flexuous, and measured 20 to 48 µm (length) × 4.5 to 5.5 µm (width). Foot cells were followed by one to two shorter cells (n = 30) that measured 8 to 12 µm (length) × 4.5 to 5.8 µm (width). The shorter cells were followed by a chain of four to eight conidia. The conidia (n = 50) were hyaline, cylindrical to ovoid, with fibrosin bodies, and measured 20 to 28 µm (length) × 10.5 to 16.5 µm (width). No chasmothecia were observed on the surface of diseased leaves. For molecular identification, the ribosomal DNA internal transcribed spacer (ITS) was amplified and sequenced using primers ITS1/ITS4 (White et al. 1990). The obtained 508-bp ITS sequence was deposited in GenBank (Accession No. ON316871). The subsequent phylogeny grouped the ITS sequence within a clade of Podosphaera pannosa sequences. Based on both morphological and phylogenetic characteristics, the powdery mildew pathogen was identified as P. pannosa (Braun et al. 2002). The voucher specimen (Accession No. GZNU-RCPP/0804/2022) were deposited at the School of Life Sciences, Guizhou Normal University, China. Pathogenicity was assessed by gently pressing naturally diseased leaves onto young leaves of three healthy, potted 2-year-old R. cymosa plants, with three non-inoculated plants as controls. Powdery mildew symptoms were observed on all inoculated plants after incubation for 10 days at 21°C, 75% relative humidity, and 12 h/12 h light/dark cycle in a greenhouse. The control plants remained symptomless. The re-isolated powdery mildew colonies on inoculated leaves were morphologically identical to those observed on the original diseased leaves, fulfilling Koch's postulates. Podosphaera pannosa has been described as the most frequent species causing powdery mildew on the Rosaceae family, particularly on Rosa spp. and Prunus spp. (Hubert et al. 2012; Félix-Gastélum et al. 2014). The occurrence of powdery mildew on R. cymosa caused by P. pannosa could pose a potential disease threat to other Rosa crops or Prunus spp.

First Report of Colletotrichum boninense Causing Anthracnose on Aucuba japonica in Guizhou Province of China.

Aucuba japonica is a plant with colorful leaves that is widely used in landscaping. Due to its shade tolerance and cold resistance (Li et al. 2013), A. japonica has become a dominant plant species in Guiyang city, China. From 2018 to 2021, an anthracnose disease was observed on A. japonica in Huaxi District (26°23'03'' N, 106°37'58'' E), Guiyang, Guizhou Province. The incidence of anthracnose in newly planted A. japonica reached 90%, resulting in a mortality rate of 30%. This has become a major disease for A. japonica in Guiyang. Typical symptoms include faded spots that initially appear at the infection center, followed by black-brown lesions with irregular edges. At the latter stage, slightly raised black spots are seen arranged in a wheel pattern. In severe cases, diseased leaves fall off. To identify the pathogen, leaf pieces (5 mm × 3 mm) containing symptomatic tissue with healthy margins were excised. The pieces were sterilized with 75% ethanol for 1 min, rinsed three times with sterile water, and cultured on potato dextrose agar (PDA) in Petri dishes at 26°C. White to cream colonies were developed after growth on PDA for 2 days. Mycelial growth ranged from 4.8 to 5.0 mm/day. Conidia were cylindrical, obtuse apex, and protruding base, with dimensions of 18.5 to 20.0 × 7.0 to 9.0 µm (n = 20). Conidial length:breadth ratio was 2-3 (n = 20). Acervuli and sclerotia had not been seen on PDA. To confirm the species of the isolate, PCR was performed on extracted DNA to amplify the ribosomal DNA internal transcribed spacer (ITS), a 200-bp intron of the glyceraldehyde-3-phosphate dehydrogenase (GAPDH), a partial sequence of the calmodulin (CAL) gene, and the large subunit (LSU) region by using the primer pairs ITS1/ITS4 (Schoch et al. 2012), GDF1/GDR1 (Guerber et al. 2003), CAL228F/CAL737R (Carbone & Kohn 1999), and NL1/NL4 (Ziemiecki et al. 1990), respectively. The obtained 553 bp ITS sequence (Genbank accession no. MZ424503) showed 99.82% similarity with several C. boninense sequences (MN429163, MN542218, KM520024, and KM520014). The obtained 233 bp GAPDH sequence (OM643394) showed 99.07% similarity with C. boninense (MT602277, GQ221769, MK544890, and MK544888). The obtained 763 bp CAL sequence (OM313386) showed 99.32% similarity with C. boninense (MK569127). The obtained 584 bp LSU sequence (OK513272) showed 99.83% similarity with C. boninense (MH876452, MH877053, and MH876450). Phylogenic trees based on the sequences of ITS, GAPDH, and CAL (Damm et al. 2012), the species of isolate was confirmed as C. boninense. To confirm pathogenicity and to fulfill Koch's postulates, leaves of five A. japonica plants were wounded with a sterilized hypodermic needle and inoculated with 1 µL of a conidial suspension (106 conidia/mL). As control, 5 plants were inoculated with 1 µL of sterile water. After 7 days in a moist climate chamber at 26°C under a 16 h/8 h light/dark cycle, symptoms appeared on all inoculated leaves, while the control leaves remained healthy. The pathogen was reisolated from the inoculated leaves, and was confirmed to be C. boninense using the same morphological and molecular methods as before. C. boninense has been reported to infect many plant species, including Capsicum annuum, Rosa chinensis, and Eucalyptus robusta (Ding et al. 2021; Tozze et al. 2009; Zhang et al. 2018). Another Colletotrichum pathogen, C. fructicola, was reported to cause anthracnose on A. japonica in China (Gong et al. 2016). To our knowledge, this is the first report of A. japonica anthracnose disease caused by C. boninense in Guizhou province, China. Identifying this pathogen provides a foundation to prevent this complex disease and to reduce economic loss.

First Report of Powdery Mildew on Photinia × fraseri Caused by Podosphaera leucotricha in Guizhou Province, China.

The evergreen shrub Photinia × fraseri is a Photinia glabra × Photinia serrulata hybrid belonging to the family Rosaceae that is widely used in ornamental landscaping. In March 2022, severe powdery mildew symptoms were observed on shrubs of Photinia × fraseri in Huaxi University Town, Guiyang, Guizhou Province, China. All observed Photinia × fraseri plants in the green belts of both roads and parks in University Town showed powdery mildew symptoms. Almost all young branches of each Photinia × fraseri individual was infected. Powdery mildew colonies covered twig tips entirely, including the stems, petioles, and the adaxial and abaxial surfaces of leaves. Infected leaves were rolled up and had irregular, dark red spots. Fungal hyphae were straight to flexuous, branched, septate, 3 to 6 µm in width, and had nipple-shaped appressoria. Conidiophores were erect, straight or somewhat flexuous, and measured 90 to 300 µm × 7 to 10.5 µm (n = 30). Foot-cells were cylindrical or subcylindrical, straight or somewhat flexuous, and measured 25 to 50 × 7 to 9.5 µm (n = 30). Foot-cells were followed by one to two shorter cells, these being 10 to 16 × 7 to 9.5 µm in size (n = 50). Shorter cells were followed by one to six conidia (most often five conidia). Conidia formed in chains, ellipsoid to ovoid in shape, having dimensions of 22.5 to 30 × 12.5 to 16 µm (n = 50), and containing fibrosin bodies. No chasmothecia (fruiting bodies) were observed. Based on these morphological characteristics, the pathogen was identified as Podosphaera leucotricha (Ellis & Everh.) E.S. Salmon (Braun & Cook 2012). To confirm this species-level identification, the ribosomal DNA internal transcribed spacer (ITS) was amplified using the primers ITS1/ITS4 (White et al. 1990). The resulting sequence was deposited in GenBank (Accession No. ON325389). When the query coverage is 100%, the obtained ITS sequence showed 99.8% identity with P. leucotricha (AB027231, MT180425, MZ298746, KX842350, and KY661036) and 100% with P. leucotricha (HM242221, KY661017, KY661028, KY661050, KY661076, KR048110, MW364489, MW364490, MZ343479, OM022112, ON073894, and ON325389), respectively. Based on the ITS sequences of Podosphaera spp., phylogenetic tree was constructed with MEGA7.0 using the Maximum Likelihood method. The ML analysis supported our isolate's putative identification as P. leucotricha. To fulfill Koch's postulates, pathogenicity testing was conducted by gently pressing naturally diseased leaves onto young leaves of three healthy, potted 1-year-old Photinia × fraseri plants; three non-inoculated healthy plants served as control. Powdery mildew symptoms were observed on 100% inoculated Photinia × fraseri plants after 12 days (in a growth chamber at 21°C under a 12 h/12 h light/dark cycle), whereas the control plants remained symptomless. The powdery mildew colonies on inoculated leaves were morphologically identical to those observed on the original diseased leaves. It is known that P. leucotricha causes powdery mildew on Photinia × fraseri in Italy (Garibaldi et al. 2005). Moreover, this fungus reportedly infected Photinia serrulata in New Zealand, Ukraine, Italy, the United States, Japan, and in East China's Shandong Province (Liang et al. 2012). To the best of our knowledge, this is the first report of powdery mildew caused by P. leucotricha on Photinia × fraseri in Southwest China's Guizhou Province. This finding is significant as P. leucotricha is the causal agent of powdery mildew on apple and pear (Strickland et al. 2021). The occurrence of said disease on Photinia × fraseri could pose a potential disease threat to these fruit crops if nearby ornamental shrubs were able to act as reservoirs for the fungus, and a means to escape agricultural management efforts.

Genome Mining Enabled by Biosynthetic Characterization Uncovers a Class of Benzoxazolinate-Containing Natural Products in Diverse Bacteria.

Benzoxazolinate is a rare bis-heterocyclic moiety that interacts with proteins and DNA and confers extraordinary bioactivities on natural products, such as C-1027. However, the biosynthetic gene responsible for the key cyclization step of benzoxazolinate remains unclear. Herein, we show a putative acyl AMP-ligase responsible for the last cyclization step. We used the enzyme as a probe for genome mining and discovered that the orphan benzobactin gene cluster in entomopathogenic bacteria prevails across Proteobacteria and Firmicutes. It turns out that Pseudomonas chlororaphis produces various benzobactins, whose biosynthesis is highlighted by a synergistic effect of two unclustered genes encoding enzymes on boosting benzobactin production; the formation of non-proteinogenic 2-hydroxymethylserine by a serine hydroxymethyltransferase; and the types I and II NRPS architecture for structural diversity. Our findings reveal the biosynthetic potential of a widespread benzobactin gene cluster.

An Unconventional Melanin Biosynthesis Pathway in Ustilago maydis.

Ustilago maydis is a phytopathogenic fungus responsible for corn smut disease. Although it is a very well-established model organism for the study of plant-microbe interactions, its potential to produce specialized metabolites, which might contribute to this interaction, has not been studied in detail. By analyzing the U. maydis genome, we identified a biosynthetic gene cluster whose activation led to the production of a black melanin pigment. Single deletion mutants of the cluster genes revealed that five encoded enzymes are required for the accumulation of the black pigment, including three polyketide synthases (pks3, pks4, and pks5), a cytochrome P450 monooxygenase (cyp4), and a protein with similarity to versicolorin B synthase (vbs1). Metabolic profiles of deletion mutants in this gene cluster suggested that Pks3 and Pks4 act in concert as heterodimers to generate orsellinic acid (OA), which is reduced to the corresponding aldehyde by Pks5. The OA-aldehyde can then react with triacetic acid lactone (TAL), also derived from Pks3/Pks4 heterodimers to form larger molecules, including novel coumarin derivatives. Our findings suggest that U. maydis synthesizes a novel type of melanin based on coumarin and pyran-2-one intermediates, while most fungal melanins are derived from 1,8-dihydroxynaphthalene (DHN) or l-3,4-dihydroxyphenylalanine (l-DOPA). Along with these observations, this work also provides insight into the mechanisms of polyketide synthases in this filamentous fungus.IMPORTANCE The fungus Ustilago maydis represents one of the major threats to maize plants since it is responsible for corn smut disease, which generates considerable economical losses around the world. Therefore, contributing to a better understanding of the biochemistry of defense mechanisms used by U. maydis to protect itself against harsh environments, such as the synthesis of melanin, could provide improved biological tools for tackling the problem and protect the crops. In addition, the fact that this fungus synthesizes melanin in an unconventional way, requiring more than one polyketide synthase for producing melanin precursors, gives a different perspective on the complexity of these multidomain enzymes and their evolution in the fungal kingdom.

Dual phenazine gene clusters enable diversification during biosynthesis.

Biosynthetic gene clusters (BGCs) bridging genotype and phenotype continuously evolve through gene mutations and recombinations to generate chemical diversity. Phenazine BGCs are widespread in bacteria, and the biosynthetic mechanisms of the formation of the phenazine structural core have been illuminated in the last decade. However, little is known about the complex phenazine core-modification machinery. Here, we report the diversity-oriented modifications of the phenazine core through two distinct BGCs in the entomopathogenic bacterium Xenorhabdus szentirmaii, which lives in symbiosis with nematodes. A previously unidentified aldehyde intermediate, which can be modified by multiple enzymatic and non-enzymatic reactions, is a common intermediate bridging the pathways encoded by these BGCs. Evaluation of the antibiotic activity of the resulting phenazine derivatives suggests a highly effective strategy to convert Gram-positive specific phenazines into broad-spectrum antibiotics, which might help the bacteria-nematode complex to maintain its special environmental niche.

An Uncommon Type II PKS Catalyzes Biosynthesis of Aryl Polyene Pigments.

Aryl polyene (APE) pigments are a widely distributed class of bacterial polyketides. So far, little is known about the biosynthesis of these compounds, which are produced by a novel type II polyketide synthase (PKS). We have identified all enzymes involved in APE biosynthesis and determined their peculiar functions. The biosynthesis was reconstituted in vitro, and ACP-bound intermediates were assigned for each reaction step by HPLC-MS. Native mass spectrometry experiments identified four stable complexes: the acyl-carrier proteins ApeE and ApeF bound to the thioesterase ApeK, the dehydratases ApeI and ApeP, and the ketosynthase ApeO in complex with its chain-length factor ApeC. X-ray structures of the heterodimeric ApeO:ApeC and ApeI:ApeP complexes depict striking protein-protein interactions. Altogether, our study elucidated mechanistic aspects of APE biosynthesis that unifies elements of type II fatty acid and PKS systems, but in addition includes novel enzyme complexes.

Cyclo(tetrahydroxybutyrate) production is sufficient to distinguish between Xenorhabdus and Photorhabdus isolates in Thailand.

Bacteria of the genera Photorhabdus and Xenorhabdus produce a plethora of natural products to support their similar symbiotic life cycles. For many of these compounds, the specific bioactivities are unknown. One common challenge in natural product research when trying to prioritize research efforts is the rediscovery of identical (or highly similar) compounds from different strains. Linking genome sequence to metabolite production can help in overcoming this problem. However, sequences are typically not available for entire collections of organisms. Here, we perform a comprehensive metabolic screening using HPLC-MS data associated with a 114-strain collection (58 Photorhabdus and 56 Xenorhabdus) across Thailand and explore the metabolic variation among the strains, matched with several abiotic factors. We utilize machine learning in order to rank the importance of individual metabolites in determining all given metadata. With this approach, we were able to prioritize metabolites in the context of natural product investigations, leading to the identification of previously unknown compounds. The top three highest ranking features were associated with Xenorhabdus and attributed to the same chemical entity, cyclo(tetrahydroxybutyrate). This work also addresses the need for prioritization in high-throughput metabolomic studies and demonstrates the viability of such an approach in future research.