Identification of Fusarium ipomoeae as the causative agent of leaf spot disease in Bletilla striata in China.

Bletilla striata (Thunb.) Rchb. f. (Orchidaceae) is traditionally used for hemostasis and detumescence in China. In April 2019, a leaf spot disease on B. striata was observed in plant nurseries in Guilin, Guangxi Province, China, with an estimated incidence of ~30%. Initial symptoms include the appearance of circular or irregular brown spots on leaf surfaces, which progressively expand into large, dark brown, necrotic areas. As lesions coalesce, large areas of the leaf die, ultimately resulting in abscission. To isolate the pathogen, representative samples exhibiting symptoms were collected, leaf tissues (5 × 5 mm) were cut from the junction of diseased and healthy tissue, surface-disinfected in 1% sodium hypochlorite solution for 2 min, rinsed three times in sterile water, plated on potato dextrose agar (PDA) medium, and incubated at 28°C (12-h light-dark cycle) for 3 days. Hyphal tips from recently germinated spores were transferred to PDA to obtain pure cultures. Nine fungal isolates with similar morphological characteristics were obtained. Colonies on PDA were villose, had a dense growth of aerial mycelia and appeared pinkish white from above and greyish orange at the center and pinkish-white at the margin on the underside. Macroconidia were smooth, and hyaline, with a dorsiventral curvature, hooked to tapering apical cells, and 3- to 5-septate. Three-septate macroconidia were 21.2 to 32.1 × 2.4 to 3.9 µm (mean ± SD: 26.9 ± 2.5 × 3.2 ± 0.4 µm, n = 30); 4-septate macroconidia were 29.5 to 38.9 × 3.0 to 4.3 µm (mean ± SD: 33.5 ± 2.6 × 3.6 ± 0.3 µm, n = 40); and 5-septate macroconidia were 39.3 to 55.6 × 4.0 to 5.4 µm (mean ± SD: 48.0 ± 3.9 × 4.5 ± 0.3 µm, n = 50). These morphological characteristics were consistent with F. ipomoeae, a member of the Fusarium incarnatum-equiseti species complex (FIESC) (Wang et al. 2019). To confirm the fungal isolate's identification, the genomic DNA of the single-spore isolate BJ-22.3 was extracted using the CTAB method (Guo et al. 2000). The internal transcribed space (ITS) region of rDNA, translation elongation factor-1 alpha (TEF-1α), and partial RNA polymerase second largest subunit (RPB2) were amplified using primer pairs [ITS1/ITS4 (White et al. 1990), EF-1/EF-2 (O'Donnell et al. 1998), and 5f2/11ar (Liu, Whelen et al. 1999, Reeb, Lutzoni et al. 2004), respectively]. The ITS (MT939248), TEF-1α (MT946880), and RPB2 (MT946881) sequences of the BJ-22.3 isolate were deposited in GenBank. BLASTN analysis of these sequences showed over 99% nucleotide sequence identity with members of the FIESC: the ITS sequence showed 99.6% identity (544/546 bp) to F. lacertarum strain NRRL 20423 (GQ505682); the TEF-1α sequence showed 99.4% similarity (673/677 bp) to F. ipomoeae strain NRRL 43637 (GQ505664); and the RPB2 sequence showed 99.6% identity (1883/1901 bp) to F. equiseti strain GZUA.1657 (MG839492). Phylogenetic analysis using concatenated sequences of ITS, TEF-1α, and RPB2 showed that BJ-22.3 clustered monophyletically with strains of F. ipomoeae. Therefore, based on morphological and molecular characteristics, the isolate BJ-22.3 was identified as F. ipomoeae. To verify the F. ipomoeae isolate's pathogenicity, nine 1.5-year-old B. striata plants were inoculated with three 5 × 5 mm mycelial discs of strain BJ-22.3 from 4-day-old PDA cultures. Additionally, three control plants were inoculated with sterile PDA discs. The experiments were replicated three times. All plants were enclosed in transparent plastic bags and incubated in a greenhouse at 26°C for 14 days. Four days post-inoculation, leaf spot symptoms appeared on the inoculated leaves, while no symptoms were observed in control plants. Finally, F. ipomoeae was consistently re-isolated from leaf lesions from the infected plants. To our knowledge, this is the first report of F. ipomoeae causing leaf spot disease on B. striata in China. The spread of this disease might pose a serious threat to the production of B. striata. Growers should implement disease management to minimize the risks posed by this pathogen.

Periostin Promotes Neural Stem Cell Proliferation and Differentiation following Hypoxic-Ischemic Injury.

Neural stem cell (NSC) proliferation and differentiation are required to replace neurons damaged or lost after hypoxic-ischemic events and recover brain function. Periostin (POSTN), a novel matricellular protein, plays pivotal roles in the survival, migration, and regeneration of various cell types, but its function in NSCs of neonatal rodent brain is still unknown. The purpose of this study was to investigate the role of POSTN in NSCs following hypoxia-ischemia (HI). We found that POSTN mRNA levels significantly increased in differentiating NSCs. The proliferation and differentiation of NSCs in the hippocampus is compromised in POSTN knockout mice. Moreover, NSC proliferation and differentiation into neurons and astrocytes significantly increased in cultured NSCs treated with recombinant POSTN. Consistently, injection of POSTN into neonatal hypoxic-ischemic rat brains stimulated NSC proliferation and differentiation in the subventricular and subgranular zones after 7 and 14 days of brain injury. Lastly, POSTN treatment significantly improved the spatial learning deficits of rats subjected to HI. These results suggest that POSTN significantly enhances NSC proliferation and differentiation after HI, and provides new insights into therapeutic strategies for the treatment of hypoxic-ischemic encephalopathy.

Role of the PTEN signaling pathway in autism spectrum disorder.

Autism is an etiologically heterogeneous group of neurodevelopmental disorders, diagnosed mostly by the clinical behavioral phenotypes. The concept that the tumor-related gene PTEN plays a critical role in autism spectrum disorder has emerged over the last decade. In this review, we focus on the essential role of the PTEN signaling pathway in neuronal differentiation and the formation of neural circuitry, as well as genetic mouse models with Pten manipulations. Particularly, accumulated data suggest that the effect of PTEN on neural stem-cell development contributes significantly to the pathophysiology of autism spectrum disorders.