First Report of Tobacco Leaf Tip Blight Caused by Alternaria gossypina in China.

Tobacco (Nicotiana tabacum L.) belongs to the family Solanaceae, an economically significant crop (Zhou et al. 2023). Twelve samples with leaf spots were collected in Keti Village, Changshun County, Zunyi City, Guizhou province, China in 2022. Twenty-five percent of the samples had dry lesions near the leaf tip which resulted leaf tip blight after development. Fungi were isolated by a previous method (Wei et al. 2022). Six Alternaria strains were obtained and preserved in the Fungal Herbarium of Yangtze University (YZU), Jingzhou, Hubei, China. Among them, one strain YZU 221477 showed distinct cultural characteristics out of five A. alternata strains, which was again determined by growing on potato dextrose agar (PDA) at 25°C for 7 days in dark to evaluate. The colonies (60 mm in diameter) were white cottony in the center surrounded by vinaceous purple. To examine the morphology, mycelia were inoculated onto potato carrot agar (PCA) at 22°C, following an 8 h light/16 h dark photoperiod (Simmons 2007). Conidia were obclavate or ovoid, normally 3-5 conidial units per chain, 20-38 × 10-16.5 µm, 3 to 5 transverse septa, beakless or a short beak (4-30 µm). The observation results were consistent with those of A. gossypina (Zhang 2003). Total genomic DNA was extracted using the CTAB method and seven gene regions including internal transcribed spacer of rDNA (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), translation elongation factor 1 alpha (TEF1), RNA polymerase second largest subunit (RPB2), Alternaria major allergen gene (Alt a 1), endopolygalacturonase (EndoPG) and an anonymous gene region (OPA10-2) were amplified with ITS5/ITS4, gpd1/gpd2, EF1-728F/EF1-986R, RPB2-5F/RPB2-7cR, Alt-for/Alt-rev, PG3/PG2b and OPA10-2L/OPA10-2R primers, respectively. All sequences were deposited in GenBank (ITS: OR710806; GAPDH: PP057862; TEF1: PP158601; RPB2: PP057863; Alt a 1: PP057865; EndoPG: PP057861; OPA10-2: PP057864). Combining with relevant sequences retrieved from the NCBI database were used for the phylogenetic analysis. Maximum Likelihood (ML) tree was constructed with RAxML v.7.2.8 employing GTRCAT model using 1000 bootstrap (BS) replicates to assess statistical support. The results indicated that the present strain grouped with A. gossypina (type strain of CBS 104.32) supported with 73% bootstrap values, also having a support of 0.83 Bayesian posterior probabilities values. Based on morphology and molecular evidence, the strain YZU 221477 is identified as Alternaria gossypina. Pathogenicity was examined to fulfill Koch's postulates. Mycelial plugs (6 mm diameter) of the present strain and A. alternata cultivated on PDA were taken from the margin and inoculated onto viable tobacco leaves (Cultivar: Yunyan 87, n=3) growing forty days, while controls were inoculated with sterile PDA. The assay was conducted three times. The plants were maintained at 25°C with humidity levels over 85% in a greenhouse. Leaves were evaluated after 7 days, necrotic spots encircled by yellow halos were on both inoculums, except controls. Pathogen re-isolation confirmed that it was the same as inoculated fungus based on morphology. A. gossypina was firstly found on cotton (Hopkins 1931), late reported to induce disease on Minneola, Nopalea, Hibiscus, Citrus, Solanum and Ageratina. To our knowledge, this is the first report of A. gossypina causing tobacco leaf tip blight in China, and it also provides a basis for controlling of tobacco leaf tip blight.

CtBP1 is involved in epithelial-mesenchymal transition and is a potential therapeutic target for hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is a highly invasive type of cancer. Metastasis is the leading cause of mortality of advanced HCC patients. In the metastasis cascade, cancer cells undergo epithelial-mesenchymal transition resulting in the loss of cell­to­cell adhesion, migration and invasion into the stroma. Loss of E-cadherin expression is a key molecular event in epithelial-mesenchymal transition through several regulatory mechanisms including epigenetic modification, regulation by inhibitory transcriptional factors and deletion of chromosome 16q24 locus. C-terminal binding protein 1 (CtBP1) functions as a corepressor binding to several transcriptional factors and suppresses E-cadherin expression. We found that CtBP1 was upregulated in HCC when compared with paired normal liver tissues and was inversely correlated with E-cadherin expression in HCC by immunohistochemical assay using tissue array. Western blot analysis confirmed the results of the immunohistochemical assays. When CtBP1 was knocked down by siRNA in HepG2 cells (a human HCC cell line), E-cadherin was upregulated and the invasive ability of HepG2 cells was inhibited. In addition, following CtBP1 knockdown, the cell viability was decreased along with increased apoptosis rather than cell cycle arrest. These data suggest a pivotal role of CtBP1 in EMT of HCC, and its potential as a therapeutic target in human disease.