Background: An ongoing outbreak of coronavirus disease 2019 (COVID-19) has spread around the world. It is debatable whether asymptomatic COVID-19 virus carriers are contagious. We report here a case of the asymptomatic patient and present clinical characteristics of 455 contacts, which aims to study the infectivity of asymptomatic carriers. Material and methods: 455 contacts who were exposed to the asymptomatic COVID-19 virus carrier became the subjects of our research. They were divided into three groups: 35 patients, 196 family members and 224 hospital staffs. We extracted their epidemiological information, clinical records, auxiliary examination results and therapeutic schedules. Results: The median contact time for patients was four days and that for family members was five days. Cardiovascular disease accounted for 25% among original diseases of patients. Apart from hospital staffs, both patients and family members were isolated medically. During the quarantine, seven patients plus one family member appeared new respiratory symptoms, where fever was the most common one. The blood counts in most contacts were within a normal range. All CT images showed no sign of COVID-19 infection. No severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections was detected in 455 contacts by nucleic acid test. Conclusion:In summary, all the 455 contacts were excluded from SARS-CoV-2 infection and we conclude that the infectivity of some asymptomatic SARS-CoV-2 carriers might be weak. IntrodutionThe emergence of the coronavirus disease 2019 (COVID-19) since early December 2019, has spread to many countries recently and sparked world pandemic via mass gathering [1][2][3]. As of March 24, 2020, there have been 334981 confirmed cases and 14652 deaths globally [4].It has been proved that the pathogen of COVID-19 is severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which has high homology with SARS-CoV [5]. Similar to SARS-CoV, the dominant SARS-CoV-2 transmission mode is human-to-human transmission [6]. Differently, the reproductive number (R0)

One-sentence summary: Map-based cloning of a gene underlying grain shape in 22 wheat suggests that modest genetic changes induce dramatic phenotypic variations 23 associated with a new wheat subspecies during evolution. ABSTRACT 29 Six subspecies of hexaploid wheat (Triticum spp.) have been identified, but the origin 30 of Indian dwarf wheat (Triticum sphaerococcum Perc.), the only subspecies with 31 round grains, is currently unknown. Here, we isolated the grain-shape gene Tasg-D1 32 in T. sphaerococcum Perc. via positional cloning. Tasg-D1 encodes a serine/threonine 33 protein kinase glycogen synthase kinase 3 (STKc_GSK3) that negatively regulates 34 brassinosteroid signaling. Expression of TaSG-D1 and the mutant form Tasg-D1 in 35 Arabidopsis thaliana suggested that a single amino acid substitution in the TREE 36 domain of TaSG-D1 enhances protein stability in response to brassinosteroids, likely 37 leading to formation of round grains in wheat. This gain-of-function mutation has 38 pleiotropic effects on plant architecture and exhibits incomplete dominance. 39 Haplotype analysis of 898 wheat accessions indicated that the origin of T. 40 sphaerococcum Perc. in ancient India involved at least two independent mutations of 41 TaSG-D1. Our results demonstrate that modest genetic changes in a single gene can 42 induced dramatic phenotypic changes. 43 44 108 glycogen synthase kinase 3 (STKc_GSK3), the wheat orthologue of BIN2. In T. 109 sphaerococcum, a single amino acid substitution of STKc_GSK3 enhances protein 110 5 stability in response to BR, leading to round grain formation. Evolutionary analysis 111 provided evidence that the origin of T. sphaerococcum wheat involved at least two 112 independent mutations of TaSG-D1.

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