No abstract

Pine wilt is a disease of pine (Pinus spp.) caused by the pine wood nematode (PWN), Bursaphelenchus xylophilus. However, the pathogenic mechanism of pine wilt disease (PWD) remains unclear. Although the PWN was thought to be the only pathogenic agent associated with this disease, a potential role for bacterial symbionts in the disease process was recently proposed. Studies have indicated that aseptic PWNs do not cause PWD in aseptic pine trees, while PWNs associated with bacteria cause wilting symptoms. To investigate the pathogenicity of the PWN and its associated bacteria, 3-month-old microcuttings derived from certain clones of Pinus densiflora Siebold & Zucc. produced in vitro were inoculated under aseptic conditions with aseptic PWNs, non-aseptic PWNs and bacteria isolated from the nematodes. Six-month-old aseptic P. densiflora microcuttings and 7-month-old P. massoniana seedlings were also inoculated under aseptic conditions with aseptic PWNs and non-aseptic PWNs. The results showed that the aseptic microcuttings and seedlings inoculated with aseptic PWNs or non-aseptic PWNs wilted, while those inoculated with bacterial isolates did not wilt. Nematodes were recovered from wilted microcuttings and seedlings inoculated with aseptic PWNs and non-aseptic PWNs, and the asepsis of nematodes recovered from aseptic PWN-inoculated microcuttings and seedlings was reconfirmed by culturing them in NB liquid medium at 30°C for more than 7 days. Taken together, the results indicate that the asepsis of PWN did not cause the loss of pathogenicity.

Prunus davidiana, which is a wild species, can be used as rootstocks for cultivation of fruit trees, breeding germplasm for improving resistance to diseases and insects, pioneer trees for recovering vegetation in arid areas, decoration trees for parks and gardens, and a potential medicinal plant for human health. Despite the valuable characteristics of P. davidiana, the genetic variations of resources of P. davidiana remain unclear. In this study, we used seven natural populations (GE; GH; ST; SF; SJ; SY; NX short for Heshui, Gansu; Huating Gansu; Taibai, Shaanxi; Fuxian, Shaanxi; Jiaocheng, Shanxi; Yangquan, Shanxi; Xiji, Ningxia, respectively) of P. davidiana collected at distribution center in China to generate a fingerprint using 15 SSR markers by multifluorophore fragment analysis to assess transportability of the markers, genetic diversity and genetic structure within and among populations. Our data show that a 92% transportability rate was found from closely related species of P. davidiana based on SSR markers developed, and DNA polymorphisms were also detected among accessions by the selected SSR markers. The SSR markers amplified 137 alleles in total for all accessions with an average value of 9.13 alleles, ranging from the highest value of 15 alleles for UDP96-013 to the lowest value of 3 alleles for CPPCT017. Rare alleles, present at less than or equal to 5% of all accessions by marker, showed the highest value in BPPCT 020. By analyzing all accessions, the majority of the 192 accessions from seven populations were found to cluster together according to the given populations, while the minority from the given populations was distributed within clusters. The SY population appeared to have the most diversity among populations, followed by the NX population according to comprehensive analysis of all indices. The seven populations analyzed by unweighted parsimony and principal coordinate analysis were divided into two groups: ST, SY and SF; NX, GE, SJ and GH. A stark difference was found in the genetic variation—with 16% among populations and 84% within populations. Our results from this study imply that most SSR markers developed from related species can be used for genetic analyses of P. davidiana; some markers have more relevant applications for genetic analyses such as UDP96-013 for diversity evaluation and BPPCT 020 for mining rare alleles in P. davidiana; SY and NX are preferred when considering conservation and agronomic utilization.

Prunus davidiana (Carrie're) Franch is a very important resource for the restoration in dry and arid areas, genetic improvement of peach, and extraction of health-promoting components. To effectively use the resource, we must have a measure of genetic diversity of P. davidiana and its population structure. LD (Linkage disequilibrium) provides information for association mapping underlying the phenotypic variation observed. Selective loci reveal adaptive evolution processes resulting from natural selection. A set of 190 genotypes from seven natural populations（SXTB, SIYQ, SXFX, NXXJ, SIJC, GSHT, GSHS) of P. davidiana collected from the range of P. davidiana in China was fingerprinted with 23 SSR markers, and analyzed with spatial structure, pairwise Fst (differentiation coefficient), PCA (principal coordinate analysis), estimation of groups of populations with STRUCTURE software, selective loci obtained from lnRH tested by standardization distribution and Grubbs. Our results demonstrate that population structure of four groups existed among populations through complementary analyses of the above mentioned methods; significant LD numbers from 22 to 129 between loci within unstructured populations were detected; there were five selective loci in all populations and two common selective loci for local natural selection between populations. We should conserve four populations among seven populations; these selective loci may provide information for disclosing adaption evolution and candidate genes according to selective loci and alleles; LDs inform how to use them for association analysis.

Background: Single-tablet regimen (STR) provides a convenient once-daily regimen for the prevention of human immunodeficiency virus (HIV) infection. Here, we investigated the safety and tolerability of coformulated bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF) as a three-drug, STR for post-exposure prophylaxis (PEP) in Chinese individuals. Methods: This was a prospective, open-label, single-arm trial conducted in a sexually transmitted diseases and acquired immunodeficiency syndrome clinic of a tertiary hospital in Beijing, China. Adults requiring PEP were prescribed BIC/FTC/TAF one pill once a day for 28 days. Clinical and laboratory data were collected and analyzed at baseline, weeks 2, 4, 8, 12, and 24. Results: Of 112 participants enrolled in the study, 109 (97.3%) were male and the mean age was 30 ± 8 years. PEP completion was 96.4% (95% confidence interval: 91.1–99.0%). Two participants stopped PEP after 2 days because the source partner was identified as HIV uninfected. One participant was excluded due to hepatitis B virus infection according to the exclusion criteria. One discontinued due to the participant's decision. No participant acquired HIV through week 24. Adherence was 98.9% (standard deviation [SD]: 3.3%) by self-reporting and 98.5% (SD: 3.5%) by pill count. Only five participants experienced mild clinical adverse events attributed to the study drug (including headache, diarrhea, and nausea) and four participants had elevated serum creatinine (grade 1). Conclusions: A once daily, STR of BIC/FTC/TAF used as PEP was safe and well-tolerated with a high rate of completion and adherence in Chinese. BIC/FTC/TAF may be a good option for PEP. Trial Registration: ChiCTR.org.cn, ChiCTR2100048080