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Reverse genetics is a useful tool for studying viruses and developing vaccines for coronaviruses. However, constructing and manipulating the coronavirus genome in Escherichia coli can be time-consuming and challenging due to its large size and instability. Homologous recombination, a genetic manipulation mechanism found in organisms, is essential for DNA repair, gene recombination, and genetic engineering. In yeast, particularly Saccharomyces cerevisiae, homologous recombination technology is commonly used for constructing gene expression plasmids and genome editing. In this study, we successfully split and spliced a 30 kb viral genome fragment using yeast homologous recombination. By optimizing the program parameters, such as homologous arm lengths and fragment-to-vector ratios, we achieved a splicing efficiency of up to 97.9%. The optimal parameters selected were a 60 bp homologous sequence size and a vector fragment ratio of 1:2:2:2:2:2 for yeast homologous recombination of large DNA fragments. [ABSTRACT FROM AUTHOR]

Cap carbonate of the early Ediacaran period represents an abrupt climate shift from severe Marinoan glaciation to a post‐glacial warm environment. Some consensuses on the distinctive negative excursion of δ13Ccarb and the origin of its unique sedimentary structures have been reached over the past decades, but certain aspects such as the distribution and redox conditions of cap carbonate still remain controversial. To resolve these issues, we collected detailed samples of the Doushantuo cap carbonate from the Ganlong‐Fanyang section and the Poutoushang reservoir section in the Danzhai County, southeast Guizhou Province, respectively. We conducted carbon and oxygen isotope analysis and trace element analysis in this study. The Ganlong‐Fanyang section was possibly situated in a submarine highland because of its higher carbon isotope than that of the Potoushang section according to the carbon isotopic gradient. Negative carbon isotope excursions at the basal Doushantuo cap carbonate from the two sections correlate well with those from other equivalent cap carbonates and were corresponding to the first one (SN1 or EN1) of the carbon isotopic curve during the Ediacaran period, implying a remarkable global event after the post‐Marinoan glaciation. Geochemical features of trace elements and rare earth elements support an overall oxygen‐rich condition with syn‐depositional or pene‐contemporaneous hydrothermal activities and methane seeps during the deposition of cap carbonate. We reconstruct a new sedimentary model that the Doushantuo cap carbonates were mainly precipitated in relatively shallow‐ to deep‐water shelf environments without disturbance by abundant terrestrial materials, which may be on isolated platforms over the early developed grabens in a deep‐water basinal condition, rather than within the entire oceanic basin. [ABSTRACT FROM AUTHOR]