Identification of CmbHLH Transcription Factor Family and Excavation of CmbHLHs Resistant to Necrotrophic Fungus Alternaria in Chrysanthemum.

Chrysanthemum morifolium Ramat. 'Huaihuang' is a traditional Chinese medicinal plant. However, a black spot disease caused by Alternaria sp., a typical necrotrophic fungus, has a serious damaging influence on the field growth, yield, and quality of the plant. 'Huaiju 2#' being bred from 'Huaihuang', shows resistance to Alternaria sp. bHLH transcription factor has been widely studied because of their functions in growth development, signal transduction, and abiotic stress. However, the function of bHLH in biotic stress has rarely been studied. To characterize the resistance genes, the CmbHLH family was surveyed in 'Huaiju 2#'. On the basis of the transcriptome database of 'Huaiju 2#' after Alternaria sp. inoculation, with the aid of the Chrysanthemum genome database, 71 CmbHLH genes were identified and divided into 17 subfamilies. Most (64.8%) of the CmbHLH proteins were rich in negatively charged amino acids. CmbHLH proteins are generally hydrophilic proteins with a high aliphatic amino acid content. Among the 71 CmbHLH proteins, five CmbHLHs were significantly upregulated by Alternaria sp. infection, and the expression of CmbHLH18 was the most significant. Furthermore, heterologous overexpression of CmbHLH18 could improve the resistance of Arabidopsis thaliana to necrotrophic fungus Alternaria brassicicola by enhancing callose deposition, preventing spores from entering leaves, reducing ROS accumulation, increasing the activities of antioxidant enzymes and defense enzymes, and promoting their gene expression levels. These results indicate that the five CmbHLHs, especially CmbHLH18, may be considered candidate genes for resistance to necrotrophic fungus. These findings not only increase our understanding of the role CmbHLHs play in biotic stress but also provide a basis by using CmbHLHs to breed a new variety of Chrysanthemum with high resistance to necrotrophic fungus.

Causal association of monounsaturated fatty acids with rheumatoid arthritis but not osteoarthritis: A two-sample Mendelian randomization study.

OBJECTIVES: Previous studies have indicated that dietary monounsaturated fatty acids (MUFAs) are associated with decreased risk of osteoarthritis (OA) and rheumatoid arthritis (RA). However, the causality of the observed associations is largely undetermined. We sought to ascertain the potential causal roles of two of the most common MUFAs, oleic acid and palmitoleic acid, in RA and OA risk using a two-sample Mendelian randomization approach. METHODS: For the outcomes, we used summary-level data for RA (14 361 people with RA and 43 923 controls) and OA (10 083 people with OA and 40 425 controls) from two genome-wide association studies in European ancestry. For the exposures, five single-nucleotide polymorphisms associated with palmitoleic acid and one associated with oleic acid with genome-wide significance (P < 5 × 10-8) were selected as instrumental variables. The causal effects were estimated using the inverse-variance weighted method with several sensitivity analyses. RESULTS: For genetically predicted levels, an increase of one SD in palmitoleic acid (odds ratio, 0.24; 95% confidence interval, 0.10-0.59; P = 0.002) and oleic acid (odds ratio, 0.78; 95% confidence interval, 0.67-0.90; P < 0.001) was significantly associated with lower risk of RA. However, genetic predisposition to either of the two individual MUFAs was not associated with OA risk. Sensitivity analyses yielded similar results. CONCLUSIONS: Our Mendelian randomization analyses suggest a causal relationship between higher genetically predicted MUFA levels and lower risks of RA. However, the causality between MUFAs and OA cannot be inferred from this study. Further research is required to unravel the role of MUFA supplementation in arthritis prevention.