Sugars will eventually be exported transporter (SWEET), a class of glucose transport proteins, is crucial in plants for glucose transport by redistribution of sugars and regulates growth, development, and stress tolerance. Although the SWEET family has been studied in many plants, little is known about its function in winter B. rapa (Brassica rapa L.). Bioinformatics approaches were adopted to identify the SWEET gene (BraSWEETs) family in B. rapa to investigate its role during overwintering. From the whole-genome data, 31 BraSWEET genes were identified. Gene expansion was realized by tandem and fragment duplication, and the 31 genes were classified into four branches by phylogenetic analysis. As indicated by exon–intron structure, cis-acting elements, MEME (Multiple EM for Motif Elicitation) motifs, and protein structure, BraSWEETs were evolutionarily conserved. According to the heat map, 23 BraSWEET genes were differentially expressed during overwintering, revealing their potential functions in response to low-temperature stress and involvement in the overwintering memory-formation mechanism. BraSWEET10 is mainly associated with plant reproductive growth and may be crucial in the formation of overwintering memory in B. rapa. The BraSWEET10 gene was cloned into B. rapa (Longyou-7, L7). The BraSWEET10 protein contained seven transmembrane structural domains. Real-time fluorescence quantitative PCR (qRT-PCR) showed that the BraSWEET10 gene responded to low-temperature stress. BraSWEET10 was localized to the cell membrane. The root length of overexpressing transgenic A. thaliana was significantly higher than that of wild-type (WT) A. thaliana under low temperatures. Our findings suggest that this gene may be important for the adaptation of winter B. rapa to low-temperature stress. Overall, the findings are expected to contribute to understanding the evolutionary links of the BraSWEET family and lay the foundation for future studies on the functional characteristics of BraSWEET genes.

Background: Adulteration of official Bupleurum chinense DC. with the morphologically similar Bupleurum marginatum Wall. ex DC. var. stenophyllum (Wolff) Shan et Y. Li poses safety risks. This study aimed to develop a rapid and visual method for differentiating these two species using a polymerase chain reaction (PCR)-coupled G-quadruplex/DNA enzyme (DNAzyme) colorimetric assay. Methods: Using species-specific single nucleotide polymorphism (SNP) loci in the internal transcribed spacer 2 (ITS2) region of ribosomal DNA, we designed forward and reverse primers tagged with the reverse complement of a G-quadruplex-forming sequence at their 5′ termini. Following PCR, the target sequences were specifically amplified, generating amplicons flanked by G-quadruplex-forming motifs at both termini. The amplicons were then subjected to thermal denaturation, after which the G-rich sequences folded into G-quadruplex structures in the presence of K+. These structures were subsequently bound to hemin to form a G-quadruplex/hemin DNAzyme with peroxidase-like activity. The DNAzyme catalyzes H2O2-mediated oxidation of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) to a blue-green product. The PCR amplification and colorimetric reaction conditions were optimized by single-factor gradient experiments. Results: The optimal conditions were determined as follows: for PCR, a final primer concentration of 0.32 μmol/L, an annealing temperature of 60 ℃, and 35 amplification cycles; for the colorimetric reaction, final concentrations of 5 μmol/L hemin and 2 mmol/L ABTS, with denaturation at 95 ℃ for 8 min, and incubation at 4 ℃ for 20 min. Validation of this assay using 21 Bupleurum samples confirmed that it specifically identified B. marginatum var. stenophyllum, while showing no cross-reactivity with B. chinense, Bupleurum scorzonerifolium Willd., or other congeneric Bupleurum species included in the study. The statistical LOD of the assay was determined to be 1 ng/μL, with a reliable naked-eye visual threshold at ≥2 ng/μL and a validated detection range extending to at least 50 ng/μL with no observable hook effect. Conclusions: This assay enables naked-eye readout with high specificity and sensitivity. It provides a promising technical platform for the rapid differentiation of B. marginatum var. stenophyllum from B. chinense, as well as a broadly adaptable research framework for the visual differentiation of congeneric adulterants in traditional Chinese medicinal materials.