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Background: Proline-rich extension-like receptor protein kinases (PERKs) are an important class of receptor kinases located in the plasma membrane, most of which play a vital role in pollen development. Results: Our study identified 25 putative PERK genes from the whole Brassica rapa genome (AA). Phylogenetic analysis of PERK protein sequences from 16 Brassicaceae species divided them into four subfamilies. The biophysical properties of the BrPERKs were investigated. Gene duplication and synteny analyses and the calculation of Ka/Ks values suggested that all 80 orthologous/paralogous gene pairs between B. rapa and A. thaliana, B. nigra and B. oleracea have experienced strong purifying selection. RNA-Seq data and qRT-PCR analyses showed that several BrPERK genes were expressed in different tissues, while some BrPERKs exhibited high expression levels only in buds. Furthermore, comparative transcriptome analyses from six male-sterile lines of B. rapa indicated that 7 BrPERK genes were downregulated in all six male-sterile lines. Meanwhile, the interaction networks of the BrPERK genes were constructed and 13 PERK coexpressed genes were identified, most of which were downregulated in the male sterile buds. Conclusion: Combined with interaction networks, coexpression and qRT-PCR analyses, these results demonstrated that two BrPERK genes, Bra001723.1 and Bra037558.1 (the orthologs of AtPERK6 (AT3G18810)), were downregulated beginning in the meiosis II period of male sterile lines and involved in anther development. Overall, this comprehensive analysis of some BrPERK genes elucidated their roles in male sterility. [ABSTRACT FROM AUTHOR]

Key message: We developed a novel Agrobacterium-mediated anther transformation for Wucai in planta, and in this procedure, the male germ line was the predominant target. Wucai (Brassica campestris L.), a variant of non-heading Chinese cabbage, is widely cultured in China and only improved by classic breeding methods. Here, a novel and efficient in planta Agrobacterium-mediated anther transformation method is developed based on the optimization of several factors that affect anther transformation. After optimization, transformation with the manual pollination application led to increased transient GUS expression in anthers (reaching 91.59%) and the transformation efficacies in planta (0.59–1.56% for four commercial cultivars). The stable integration and inheritance of the transgenes were further examined by molecular and genetic analyses. Three T2 transgenic lines presented a segregation ratio of 3:1, which was consistent with the Mendelian feature of a single dominant gene. In addition, the GUS histochemical assay and genetic crossing analysis revealed that the male germ line was the predominant target in this transformation. This optimized transformation system could provide a useful tool for both the improvement of cultivar qualities and investigation of functional genes in Wucai. [ABSTRACT FROM AUTHOR]

Background: Wucai (Brassica campestris L. ssp. chinensis var. rosularis Tsen) is a variant of nonheading Chinese cabbage (Brassica campestris L.), which is one of the major vegetables in China. Cytoplasmic male sterility (CMS) has been used for Wucai breeding in recent years. However, the underlying molecular mechanism of Wucai CMS remains unclear. In this study, the phenotypic and cytological features of Wucai CMS were observed by anatomical analysis, and a comparative transcriptome analysis was carried out to identify genes related to male sterility using Illumina RNA sequencing technology (RNA-Seq). Results: Microscopic observation demonstrated that tapetum development was abnormal in the CMS line, which failed to produce fertile pollen. Bioinformatics analysis detected 4430 differentially expressed genes (DEGs) between the fertile and sterile flower buds. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed to better understand the functions of these DEGs. Among the DEGs, 35 genes (53 DEGS) were implicated in anther and pollen development, and 11 genes were involved in pollen cell wall formation and modification; most of these showed downregulated expression in sterile buds. In addition, several genes related to tapetum development (A6, AMS, MS1, MYB39, and TSM1) and a few genes annotated to flowering (CO, AP3, VIN3, FLC, FT, and AGL) were detected and confirmed by qRT-PCR as being expressed at the meiosis, tetrad, and uninucleate microspore stages, thus implying possible roles in specifying or determining the fate and development of the tapetum, male gametophyte and stamen. Moreover, the top four largest transcription factor families (MYB, bHLH, NAC and WRKY) were analyzed, and most showed reduced expression in sterile buds. These differentially expressed transcription factors might result in abortion of pollen development in Wucai. Conclusion: The present comparative transcriptome analysis suggested that many key genes and transcription factors involved in anther development show reduced gene expression patterns in the CMS line, which might contribute to male sterility in Wucai. This study provides valuable information for a better understanding of CMS molecular mechanisms and functional genome studies in Wucai. [ABSTRACT FROM AUTHOR]

Pollen coat proteins (PCPs) are cysteine-rich small-molecule proteins, which exhibit high levels of polymorphism and are expressed in gametocytes. Previous investigations have revealed that PCP genes are involved in pollen wall synthesis, pollen-stigma recognition, and pollen development and germination. However, gene expression and function of PCP family in pollen development is not well understood in Wucai (Brassica campestris L.). In this study, genome-wide identification and expression analysis of the BcPCP gene family members were conducted, including their physical and chemical properties, chromosome localization, phylogenetic relationships, gene structure, and tertiary structure. A total of 20 BcPCP genes were identified and classified into three subfamilies showing high homology to Arabidopsis thaliana. Expression pattern analysis indicated that the BcPCP gene family exhibits higher expression levels in reproductive organs, suggesting their potential involvement in the reproductive development. Notably, BraA02g002400.3 C, potentially associated with male sterility, was identified through multiple transcriptomic and proteomic datasets. Subsequently, sequence analysis revealed its homology with the Arabidopsis GRP20 gene, and thus it was named BcGRP20. Functional analysis of this gene showed that overexpression of BcGRP20 gene in the Arabidopsis grp20 mutant could restore anther fertility. Overall, our findings indicate that BcGRP20 plays a critical role in pollen development and may be the causative gene for male sterility in Wucai. This study provides candidate genes for further functional identification of BcPCP genes in Wucai, which are crucial for anther development. [ABSTRACT FROM AUTHOR]

[Display omitted] • A triphasic intergrowth Na/Mn/Zn-based hexacyanoferrate is fabricated. • A gradient Zn/Mn distribution is formed in Na/Mn/Zn-based hexacyanoferrate. • Simultaneous surface/bulk modifications are achieved through a one-step reaction. • Na/Mn/Zn-based hexacyanoferrate exhibits significantly improved cycling stability. As a high-capacity, high-voltage, and low-cost cathode material for sodium-ion batteries (SIBs), Na/Mn-based hexacyanoferrates (Na x Mn[Fe(CN) 6 ] 1−y ·□ y ·nH 2 O) typically exhibit poor structural reversibility and interfacial stability during cycling. In this study, we report the in-situ construction of a triphasic intergrowth Na/Mn/Zn-based hexacyanoferrate (mcr-Zn 0.2 Mn 0.8) with concentration-gradient Zn distribution by an anion-controlled fractional precipitation route. Density functional theory calculations verify that the unique heterostructure arises from the different binding energies between cations and anions. A small amount of Zn2+ doping in the inner cubic/monoclinic phases enhances their structural reversibility during cycling by impeding lattice deformation induced by the Jahn–Teller effect of Mn3+. Meanwhile, the rhombohedral Zn-based hexacyanoferrate epitaxially grown on the surface diminishes the particle size of mcr-Zn 0.2 Mn 0.8 resulting in short Na+ diffusion distance, and provides interface protection that suppresses detrimental electrolyte decomposition. Consequently, mcr-Zn 0.2 Mn 0.8 exhibits a high discharge capacity of 121.1 mAh/g at 15 mA g−1, improved cycling stability at 750 mA g−1 with a capacity retention of 65.0 % after 2000 cycles, and enhanced rate capability with a discharge capacity of 71.4 mAh/g at 6000 mA g−1. The successful implementation of simultaneous surface and bulk modifications through a one-step reaction opens new possibilities for developing high-performance hexacyanoferrate cathode materials for SIBs. [ABSTRACT FROM AUTHOR]

[Display omitted] • A triphasic intergrowth Na/Mn/Zn-based hexacyanoferrate is fabricated. • A gradient Zn/Mn distribution is formed in Na/Mn/Zn-based hexacyanoferrate. • Simultaneous surface/bulk modifications are achieved through a one-step reaction. • Na/Mn/Zn-based hexacyanoferrate exhibits significantly improved cycling stability. As a high-capacity, high-voltage, and low-cost cathode material for sodium-ion batteries (SIBs), Na/Mn-based hexacyanoferrates (Na x Mn[Fe(CN) 6 ] 1−y ·□ y ·nH 2 O) typically exhibit poor structural reversibility and interfacial stability during cycling. In this study, we report the in-situ construction of a triphasic intergrowth Na/Mn/Zn-based hexacyanoferrate (mcr-Zn 0.2 Mn 0.8) with concentration-gradient Zn distribution by an anion-controlled fractional precipitation route. Density functional theory calculations verify that the unique heterostructure arises from the different binding energies between cations and anions. A small amount of Zn2+ doping in the inner cubic/monoclinic phases enhances their structural reversibility during cycling by impeding lattice deformation induced by the Jahn–Teller effect of Mn3+. Meanwhile, the rhombohedral Zn-based hexacyanoferrate epitaxially grown on the surface diminishes the particle size of mcr-Zn 0.2 Mn 0.8 resulting in short Na+ diffusion distance, and provides interface protection that suppresses detrimental electrolyte decomposition. Consequently, mcr-Zn 0.2 Mn 0.8 exhibits a high discharge capacity of 121.1 mAh/g at 15 mA g−1, improved cycling stability at 750 mA g−1 with a capacity retention of 65.0 % after 2000 cycles, and enhanced rate capability with a discharge capacity of 71.4 mAh/g at 6000 mA g−1. The successful implementation of simultaneous surface and bulk modifications through a one-step reaction opens new possibilities for developing high-performance hexacyanoferrate cathode materials for SIBs. [ABSTRACT FROM AUTHOR]

Background: Microspore embryogenesis is an extraordinarily complicated process, comprehensively regulated by a composite network of physiological and molecular factors, among which hormone is one of the most crucial factors. Auxin is required for stress-induced microspore reprogramming, however, the mechanism of its regulation of microspore embryogenesis is still unclear. Results: In this study, we found exogenously spraying 100 mg·L− 1 IAA on the buds of Wucai significantly increased the rate of microspore embryogenesis, and moreover accelerated the process of embryogenesis. Physiological and biochemical tests showed that the contents of amino acids, soluble total sugar, soluble protein, and starch were significantly increased after IAA treatment. Furthermore, exogenously spraying 100 mg·L− 1 IAA significantly enhanced IAA, GA4, and GA9 content, increased catalase (CAT) and malondialdehyde (MDA) activity, and reduced abscisic acid (ABA), MDA and soluble protopectin content, H2O2 and O2·− production rate in the bud with the largest population of late-uninucleate-stage microspores. Transcriptome sequencing was performed on buds respectively treated with 100 mg·L− 1 IAA and fresh water. A total of 2004 DEGs were identified, of which 79 were involved in micropores development, embryonic development and cell wall formation and modification, most of which were upregulated. KEGG and GO analysis revealed that 9.52% of DEGs were enriched in plant hormone synthesis and signal transduction pathways, pentose and glucuronic acid exchange pathways, and oxidative phosphorylation pathways. Conclusions: These findings indicated that exogenous IAA altered the contents of endogenous hormone content, total soluble sugar, amino acid, starch, soluble protein, MDA and protopectin, the activities of CAT and peroxidase (POD), and the production rate of H2O2 and O2·−. Combined with transcriptome analysis, it was found that most genes related to gibberellin (GA) and Auxin (IAA) synthesis and signal transduction, pectin methylase (PME) and polygalacturonase (PGs) genes and genes related to ATP synthesis and electron transport chain were upregulated, and genes related to ABA synthesis and signal transduction were downregulated. These results indicated that exogenous IAA treatment could change the balance of endogenous hormones, accelerate cell wall degradation, promote ATP synthesis and nutrient accumulation, inhibit ROS accumulation, which ultimately promote microspore embryogenesis. [ABSTRACT FROM AUTHOR]

Wucai (Brassica campestris L. ssp. chinensis var. rosularis Tsen) belongs to the Brassica genus of the Cruciferae family, and its leaf curl is a typical feature that distinguishes Wucai from other nonheading cabbage subspecies. Our previous research found that plant hormones were involved in the development of the leaf curl in Wucai. However, the molecular mechanisms and the hormones regulating the formation of leaf curl in Wucai have not yet been reported. This study aimed to understand the molecular functions related to hormone metabolism during the formation of leaf curl in Wucai. A total of 386 differentially expressed genes (DEGs) were identified by transcriptome sequencing of two different morphological parts of the same leaf of Wucai germplasm W7‐2, and 50 DEGs were found to be related to plant hormones, which were mainly involved in the auxin signal transduction pathway. Then, we measured the content of endogenous hormones in two different forms of the same leaf of Wucai germplasm W7‐2. A total of 17 hormones with differential content were identified, including auxin, cytokinins, jasmonic acids, salicylic acids, and abscisic acid. And we found that treatment with auxin transport inhibitor N‐1‐naphthylphthalamic acid can affect the leaf curl phenotype of Wucai and pak choi (Brassica rapa L. subsp. Chinensis). These results indicated that plant hormones, especially auxin, are involved in developing the leaf curl of Wucai. Our findings provide a potentially valuable reference for future research on the development of leaf curls. [ABSTRACT FROM AUTHOR]

Wucai (Brassica campestris L.) is a leafy vegetable that originated in China, its soluble sugars accumulate significantly to improve taste quality during maturation, and it is widely accepted by consumers. In this study, we investigated the soluble sugar content at different developmental stages. Two periods including 34 days after planting (DAP) and 46 DAP, which represent the period prior to and after sugar accumulation, respectively, were selected for metabolomic and transcriptomic profiling. Differentially accumulated metabolites (DAMs) were mainly enriched in the pentose phosphate pathway, galactose metabolism, glycolysis/gluconeogenesis, starch and sucrose metabolism, and fructose and mannose metabolism. By orthogonal projection to latent structures-discriminant s-plot (OPLS-DA S-plot) and MetaboAnalyst analyses, D-galactose and β-D-glucose were identified as the major components of sugar accumulation in wucai. Combined with the transcriptome, the pathway of sugar accumulation and the interact network between 26 DEGs and the two sugars were mapped. CWINV4, CEL1, BGLU16, and BraA03g023380.3C had positive correlations with the accumulation of sugar accumulation in wucai. The lower expression of BraA06g003260.3C, BraA08g002960.3C, BraA05g019040.3C, and BraA05g027230.3C promoted sugar accumulation during the ripening of wucai. These findings provide insights into the mechanisms underlying sugar accumulation during commodity maturity, providing a basis for the breeding of sugar-rich wucai cultivars. [ABSTRACT FROM AUTHOR]

Late embryogenesis abundant (LEA) proteins are important developmental proteins in the response of plants to abiotic stress. In our previous study, BcLEA73 was differentially expressed under low-temperature stress. Herein, we combined bioinformatics analysis, subcellular localization, expression assays, and stress experiments (including salt, drought, and osmotic stress) to identify and analyze the BcLEA gene family. Gene cloning and functional analysis of BcLEA73 were performed in tobacco and Arabidopsis. Based on the sequence homology and the available conservative motif, 82 BrLEA gene family members were identified and were divided into eight subfamilies in the genome-wide database of Chinese cabbage. The analysis showed that the BrLEA73 gene was located on chromosome A09 and belonged to the LEA_6 subfamily. Quantitative real-time PCR analysis indicated that the BcLEA genes were differentially expressed to varying degrees in the roots, stems, leaves, and petioles of Wucai. The overexpressed BcLEA73 transgenic plants exhibited no significant differences in root length and seed germination rates compared to the wild-type (WT) plants under control conditions. Under salt and osmotic stress treatment, the root length and seed germination rates of the BcLEA73-OE strain were significantly greater than those of WT plants. Under salt stress, the total antioxidant capacity (T-AOC) of the BcLEA73-OE lines increased significantly, and the relative conductivity, (REL), hydrogen peroxide (H2O2) content, and superoxide anion (O2−) production rate decreased significantly. Under drought treatment, the survival rate of the BcLEA73-OE lines was significantly higher than that of WT plants. These results showed that the BcLEA73 gene of Wucai functions in enhancing the tolerance of plants to salt, drought, and osmotic stress. This study provides a theoretical basis to explore the relevant functions of the BcLEA gene family members of Wucai. [ABSTRACT FROM AUTHOR]

• In this study, 27 Lhcb gene family members were identified in B. rapa. • Through transcriptome data analysis and RT-qPCR, we identified a crucial gene, BcLhcb2.1 , localized in chloroplasts, that is highly expressed in leaves. • Overexpression of BcLhcb2.1 was associated with enhanced tolerance to cold, salt, and drought stresses in Arabidopsis. Light-harvesting chlorophyll a/b-binding (Lhcb) proteins play key roles in light energy capture and transfer, leaf development, plant growth, and various stress responses. However, their role in Wucai (Brassica campestris L.) has not yet been studied. In this study, 27 Lhcb genes were identified in Brassica rapa. Chromosomal location analysis revealed that these 27 genes are distributed on nine chromosomes. Subcellular localization analysis indicated that many BrLhcb proteins were present in the chloroplast. The number of exons and introns in BrLhcb family genes was in the range of 1–7 and 0–6, respectively. Cis-acting element analysis of the BrLhcb promoters demonstrated that light-responsive elements were the most common along with elements related to stress and stress-related hormonal signals. In addition, an evolutionary analysis indicated a closer relationship between Lhcb genes of B. rapa and A. thaliana compared with the other three Brassica species. Through transcriptome data analysis and quantitative reverse transcription polymerase chain reaction (RT-qPCR), we identified a crucial gene, BcLhcb2.1 , which is localized in chloroplasts and is highly expressed in leaves. Overexpression of BcLhcb2.1 enhanced cold, salt, and drought tolerance in Arabidopsis. This study provides a theoretical basis for exploring the functions of the BrLhcb gene family and for identifying and screening stress-resistance genes. [ABSTRACT FROM AUTHOR]

In plants, the accumulation of carotenoids can maintain the balance of the photosystem and improve crop nutritional quality. Therefore, the molecular mechanisms underlying carotenoid synthesis and accumulation should be further explored. In this study, carotenoid accumulation differed significantly among parental Brassica rapa. Genetic analysis was carried out using the golden inner leaf '1900264′ line and the light−yellow inner leaf '1900262′ line, showing that the golden inner leaf phenotype was controlled by a single dominant gene. Using bulked−segregant analysis sequencing, BraA09g007080.3C encoding the ORANGE protein was selected as a candidate gene. Sequence alignment revealed that a 4.67 kb long terminal repeat insertion in the third exon of the BrGOLDEN resulted in three alternatively spliced transcripts. The spatiotemporal expression results indicated that BrGOLDEN might regulate the expression levels of carotenoid−synthesis−related genes. After transforming BrGOLDEN into Arabidopsis thaliana, the seed−derived callus showed that BrGOLDENIns and BrGOLDENDel lines presented a yellow color and the BrGOLDENLdel line presented a transparent phenotype. In addition, using the yeast two−hybrid assay, BrGOLDENIns, BrGOLDENLdel, and Brgoldenwt exhibited strong interactions with BrPSY1, but BrGOLDENDel did not interact with BrPSY1 in the split−ubiquitin membrane system. In the secondary and 3D structure analysis, BrGOLDENDel was shown to have lost the PNFPSFIPFLPPL sequences at the 125 amino acid position, which resulted in the α−helices of BrGOLDENDel being disrupted, restricting the formation of the 3D structure and affecting the functions of the protein. These findings may provide new insights into the regulation of carotenoid synthesis in B. rapa. [ABSTRACT FROM AUTHOR]

Dehydration responsive element binding protein (DREB) is a significant transcription factor class known to be implicated in abiotic stresses. In this study, we systematically conducted a genome-wide identification and expression analysis of the DREB gene family, including gene structures, evolutionary relationships, chromosome distribution, conserved domains, and expression patterns. A total of 65 DREB family gene members were identified in Chinese cabbage (Brassica rapa L.) and were classified into five subgroups based on phylogenetic analysis. Through analysis of the conserved domains of BrDREB family genes, only one exon existed in the gene structure. Through the analysis of cis-acting elements, these genes were mainly involved in hormone regulation and adversity stress. In order to identify the function of BrDREB2B, overexpressed transgenic Arabidopsis was constructed. After different stress treatments, the germination rate, root growth, survival rate, and various plant physiological indicators were measured. The results showed that transgenic Arabidopsis thaliana plants overexpressing BrDREB2B exhibited enhanced tolerance to salt, heat and drought stresses. Taken together, our results are the first to report the BrDREB2B gene response to drought and heat stresses in Chinese cabbage and provide a basis for further studies to determine the function of BrDREBs in response to abiotic stresses. [ABSTRACT FROM AUTHOR]

A spontaneous male-sterile mutant ms01 was discovered from the excellent high-generation inbred line 'hx12-6-3' in wucai. Compared with wild-type 'hx12-6-3', ms01 displayed complete male sterility with degenerated stamens and no pollen. In this study, cytological observation revealed that the tapetum of the anthers of ms01 had degraded in advance, and microspore development had stagnated in the mononuclear stage, ultimately resulting in completely aborted pollen. Genetic analysis indicated that the sterility of ms01 was controlled by a single recessive nuclear gene. In the differential proteomic analysis of 'hx12-6-3' and ms01 flower buds using a tandem mass tags-based approach, a comparison of two stages (stage a and stage e) revealed 1272 differentially abundant proteins (DAPs). The abnormal variation of the anther cuticle, pollen coat, and sporopollenin production were effected by lipid metabolism and phenylpropanoid biosynthesis in the mutant ms01. Further analysis elucidated that pollen development was associated with amino acid metabolism, protein synthesis and degradation, carbohydrate metabolism, flavonoid biosynthesis and glutathione metabolism. These results provide novel insights into the molecular mechanism of GMS (genic male sterility) in wucai. ms01 , as the first indentified spontaneous male-sterile mutant in wucai, plays a significant role in the initial study of GMS (genic male sterility). In our study, the key DAPs related to anther and pollen development were obtained by TMT-based comparative proteomic analysis. We found that the abnormal accumulation of H 2 O 2 might induce premature degradation of the tapetum, causing anther metabolism disorder and pollen abortion. This process involved multiple DAPs and formed a complex regulatory network that generated a series of physiological metabolic alterations, ultimately leading to male sterility. Our results provide a theoretical foundation for further research on the complex anther and pollen development process. H 2 O 2 might act as a signal to induce the occurrence of tapetum PCD in wucai ms01. The premature degradation of the tapetum caused anther metabolism disorder, including that of phenylpropanoid metabolism, lipid metabolism, amino acid metabolism, carbohydrate metabolism and its related metabolic pathways, which manifested as the inhibition of the AsA-GSH cycle in the anthers of ms01 at stage e.The excessive accumulation of H 2 O 2 was accompanied by deficiencies in antioxidants and antioxidative enzymes, further resulting in the degeneration of the tapetum. This ultimately led to the disorganized supply of nutrients and structural substances during pollen development. [Display omitted] • ms01 is the first indentified spontaneous male-sterile mutant in wucai. • The abnormal accumulation of H 2 O 2 might induce premature degradation of the tapetum, causing anther metabolism disorder. • The formation of the anther cuticle and sporopollenin is influenced by lipid metabolism and phenylpropanoid biosynthesis. • Pollen development is associated with amino acid metabolism, flavonoid biosynthesis and carbohydrate metabolism. • Protein synthesis and degradation by responsing endoplasmic reticulum stress is a potential pathway in male sterility. [ABSTRACT FROM AUTHOR]

Background: Chlorophyll (Chl) is a vital photosynthetic pigment involved in capturing light energy and energy conversion. In this study, the color conversion of inner-leaves from green to yellow in the new wucai (Brassica campestris L.) cultivar W7–2 was detected under low temperature. The W7–2 displayed a normal green leaf phenotype at the seedling stage, but the inner leaves gradually turned yellow when the temperature was decreased to 10 °C/2 °C (day/night), This study facilitates us to understand the physiological and molecular mechanisms underlying leaf color changes in response to low temperature. Results: A comparative leaf transcriptome analysis of W7–2 under low temperature treatment was performed on three stages (before, during and after leaf color change) with leaves that did not change color under normal temperature at the same period as a control. A total of 67,826 differentially expressed genes (DEGs) were identified. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway and Gene Ontology (GO) analysis revealed that the DEGs were mainly enriched in porphyrin and Chl metabolism, carotenoids metabolism, photosynthesis, and circadian rhythm. In the porphyrin and chlorophyll metabolic pathways, the expression of several genes was reduced [i.e. magnesium chelatase subunit H (CHLH)] under low temperature. Almost all genes [i.e. phytoene synthase (PSY)] in the carotenoids (Car) biosynthesis pathway were downregulated under low temperature. The genes associated with photosynthesis [i.e. photosystem II oxygen-evolving enhancer protein 1 (PsbO)] were also downregulated under LT. Our study also showed that elongated hypocotyl5 (HY5), which participates in circadian rhythm, and the metabolism of Chl and Car, is responsible for the regulation of leaf color change and cold tolerance in W7–2. Conclusions: The color of inner-leaves was changed from green to yellow under low temperature in temperature-sensitive mutant W7–2. Physiological, biochemical and transcriptomic studies showed that HY5 transcription factor and the downstream genes such as CHLH and PSY, which regulate the accumulation of different pigments, are required for the modulation of leaf color change in wucai under low temperature. [ABSTRACT FROM AUTHOR]

Background: Wucai (Brassica campestris L. ssp. chinensis var. rosularis Tsen) is a cold-tolerant plant that is vulnerable to high temperature. This study explored the response mechanism of wucai to low temperature. In this study, wucai seedlings were treated with different temperatures, including low temperature (LT), high temperature (HT), and a control. Results: According to transcriptomics analysis, the number of differentially expressed genes (DEGs) in HT and LT was 10,702 and 7267, respectively, compared with the control. The key genes associated with the physiological response of wucai to the treatments were analyzed. The Kyoto Encyclopedia of Genes and Genomes and Gene Ontology annotations indicated the importance of the photosynthesis and photosynthetic-antenna protein pathways. We found that a high-temperature environment greatly inhibited the expression of important genes in the photosynthetic pathway (BrLhc superfamily members, PsaD, PsaE, PsaD, PsaD, PsbO, PsbP, PsbQ, PsbR, PsbS, PsbW, PsbY, Psb27, and Psb28), whereas low temperature resulted in the expression of certain key genes (BrLhc superfamily members, Psa F, Psa H, Psb S, Psb H, Psb 28). In addition, the wucai seedlings exhibited better photosynthetic performance under low-temperature conditions than high-temperature conditions. Conclusions: Based on the above results, we speculate that upon exposure to low temperature, the plants developed higher cold tolerance by upregulating the expression of genes related to photosynthesis. Conversely, high-temperature stress inhibited the expression of pivotal genes and weakened the self-regulating ability of the plants. [ABSTRACT FROM AUTHOR]

Background: The discovery of male sterile materials is of great significance for the development of plant fertility research. Wucai (Brassica campestris L. ssp. chinensis var. rosularis Tsen) is a variety of non-heading Chinese cabbage. There are few studies on the male sterility of wucai, and the mechanism of male sterility is not clear. In this study, the male sterile mutant MS7–2 and the wild-type fertile plant MF7–2 were studied. Results: Phenotypic characteristics and cytological analysis showed that MS7–2 abortion occurred at the tetrad period. The content of related sugars in the flower buds of MS7–2 was significantly lower than that of MF7–2, and a large amount of reactive oxygen species (ROS) was accumulated. Through transcriptome sequencing of MS7–2 and MF7–2 flower buds at three different developmental stages (a–c), 2865, 3847, and 4981 differentially expressed genes were identified in MS7–2 at the flower bud development stage, stage c, and stage e, respectively, compared with MF7–2. Many of these genes were enriched in carbohydrate metabolism, phenylpropanoid metabolism, and oxidative phosphorylation, and most of them were down-regulated in MS7–2. The down-regulation of genes involved in carbohydrate and secondary metabolite synthesis as well as the accumulation of ROS in MS7–2 led to pollen abortion in MS7–2. Conclusions: This study helps elucidate the mechanism of anther abortion in wucai, providing a basis for further research on the molecular regulatory mechanisms of male sterility and the screening and cloning of key genes in wucai. [ABSTRACT FROM AUTHOR]

Background: Leaf color mutants are the ideal materials to explore the pathways of chlorophyll (Chl) metabolism, chloroplast development, and photosynthesis system. In this study, a spontaneous yellow-green leaf wucai (Brassica campestris L.) mutant "WY16–13" was identified, which exhibited yellow-green leaf color during its entire growth period. However, current understanding of the molecular mechanism underlying Chl metabolism and chloroplast development of "WY16–13" is limited. Results: Total Chl and carotenoid content in WY16–13 was reduced by 60.92 and 58.82%, respectively, as compared with its wild type parental line W16–13. Electron microscopic investigation revealed fewer chloroplasts per cell and looser stroma lamellae in WY16–13 than in W16–13. A comparative transcriptome profiling was performed using leaves from the yellow-green leaf type (WY16–13) and normal green-leaf type (W16–13). A total of 54.12 million (M) (WY16–13) and 56.17 M (W16–13) reads were generated. A total of 40,578 genes were identified from the mapped libraries. We identified 3882 differentially expressed genes (DEGs) in WY16–13 compared with W16–13 (i.e., 1603 upregulated genes and 2279 downregulated genes). According to the Gene Ontology (GO) term and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses, these DEGs are involved in porphyrin and Chl metabolism [i.e., chlorophyllase (CLH), heme oxygenase (HO), chlorophyll (ide) b reductase (NYC), and protochlorophyllide oxidoreductase (POR) genes], carbohydrate metabolism, photosynthesis, and carbon fixation in photosynthetic organisms. Moreover, deficiency in Chl biosynthetic intermediates in WY16–13 revealed that the formation of the yellow-green phenotype was related to the disorder of heme metabolism. Conclusions: Our results provide valuable insights into Chl deficiency in the yellow-green leaf mutant and a bioinformatics resource for further functional identification of key allelic genes responsible for differences in Chl content. [ABSTRACT FROM AUTHOR]

Background: Vernalization is a type of low temperature stress used to promote rapid bolting and flowering in plants. Although rapid bolting and flowering promote the reproduction of Chinese cabbages (Brassica rapa L. ssp. pekinensis), this process causes their commercial value to decline. Clarifying the mechanisms of vernalization is essential for its further application. We performed RNA sequencing of gradient-vernalization in order to explore the reasons for the different bolting process of two Chinese cabbage accessions during vernalization. Results: There was considerable variation in gene expression between different-bolting Chinese cabbage accessions during vernalization. Comparative transcriptome analysis and weighted gene co-expression network analysis (WGCNA) were performed for different-bolting Chinese cabbage during different vernalization periods. The biological function analysis and hub gene annotation of highly relevant modules revealed that shoot system morphogenesis and polysaccharide and sugar metabolism caused early-bolting 'XBJ' to bolt and flower faster; chitin, ABA and ethylene-activated signaling pathways were enriched in late-bolting 'JWW'; and leaf senescence and carbohydrate metabolism enrichment were found in the two Chinese cabbage-related modules, indicating that these pathways may be related to bolting and flowering. The high connectivity of hub genes regulated vernalization, including MTHFR2, CPRD49, AAP8, endoglucanase 10, BXLs, GATLs, and WRKYs. Additionally, five genes related to flower development, BBX32 (binds to the FT promoter), SUS1 (increases FT expression), TSF (the closest homologue of FT), PAO and NAC029 (plays a role in leaf senescence), were expressed in the two Chinese cabbage accessions. Conclusion: The present work provides a comprehensive overview of vernalization-related gene networks in two different-bolting Chinese cabbages during vernalization. In addition, the candidate pathways and hub genes related to vernalization identified here will serve as a reference for breeders in the regulation of Chinese cabbage production. [ABSTRACT FROM AUTHOR]

The quality of green leafy vegetables is easily lost during the postharvest period. The effect of exogenous 24‐epibrassinolide (EBR) pretreatment on the quality of wucai was evaluated in the present study. Wucai plants were sprayed twice with 0.1 μM EBR before harvesting. Two storage temperatures were tested: 25°C and 4°C. At 4°C, EBR pretreatment significantly delayed the degradation of the pigment and plant water loss. Furthermore, we measured the activity of key enzymes of the ascorbic acid (AsA)‐glutathione (GSH) cycle, the content of the main metabolites, and the expression of the AsA metabolism‐related genes in leaves. The results indicated that all three plants showed stronger antioxidant capacity after EBR pretreatment. At 4°C and 25°C, the storage time of wucai was 20 days and 7 days after EBR treatment, while the samples could be stored for 14 days and 4 days without EBR treatment application, respectively. At 4°C, the nutritional properties of wucai pretreated with EBR, such as total free amino acids, total soluble sugar, and cellulose contents, were higher than those of the control, while the content of nitrite and lignin was lower than that of the control. Hence, EBR pretreatment was able to enhance the antioxidant capacity of wucai, maintain normal leaf color and shape during storage, and delay the decline of nutritional properties; therefore, EBR pretreatment has potential commercial value for prolonging the market life of wucai. [ABSTRACT FROM AUTHOR]

• The tapetum was abnormally vacuolated after meiosis in Wucai ogu-CMS, which led to the abortion of microspores. • The TDF1 gene is essential for early tapetal development. • Constitutive expression of BrTDF1 in the Arabidopsis tdf1 mutant transgenic lines could restore its fertility. Ogura cytoplasmic male sterility (ogu -CMS) has been widely used by breeders for vegetables in the genus Brassica ; however, the molecular mechanism of this male sterility remains unclear. The tapetum plays a crucial role in anther development by providing nutrients and secreting callose for pollen development. In this study, we found that the tapetum was abnormally vacuolated after meiosis in Wucai ogu -CMS, which led to the abortion of microspores. The TDF1 gene is essential for early tapetal development. Combined with the characteristics of abortion in ogu -CMS, qRT-PCR analysis showed that the BrTDF1 gene was expressed in all detected tissues from fertile plants, and the transcript levels of this gene in fertile buds were far higher than those in vegetative organs. Compared with the fertile line, BrTDF1 exhibited lower expression in all developmental stages of buds from the sterile line. In addition, the examinations of A6 and EXPB5 genes suggested that the expressions of these genes in ogu -CMS were lower than those in its maintainer line. Further analysis of its function showed that constitutive expression of BrTDF1 in the Arabidopsis tdf1 mutant transgenic lines could restore its fertility. These results indicated that this MYB transcription factor BrTDF1 is required for tapetal development in Wucai. [ABSTRACT FROM AUTHOR]

• Exogenous IAA improved photosynthetic capacity and carbohydrate metabolism in Zizania latifolia. • IAA could significantly improve plant yield. • IAA obviously promoted the integration of plant cell wall and hyphae of Ustilago esculenta Henn. • TIBA can reversely prove that exogenous IAA to improve plant yield, photosynthesis capacity, carbon assimilation. The effects of plant hormones on plant growth of Zizania latifolia are still considered to be the difficult and hot spots. The present study was carried out to investigate the regulation mechanism of exogenous indole-3-acetic acid (IAA) and IAA transport inhibitor (2,3,5-triiodobenzoic acid, TIBA) on yield, photosynthesis capacity, carbon assimilation and interaction of plant-fugal of Ustilago esculenta Henn. These results displayed that exogenous IAA led to significant increases in gall growth rate, swollen gall volume and biomass accumulation, promoting yield per unit of swollen gall in Z. latifolia. Exogenous IAA could improve the net photosynthetic rate (Pn), which contributed to higher stomatal conductance (Gs) and transpiration rate (Tr) in plant. TIBA treatment markedly inhibited the plant growth and photosynthetic rate. Contents of sucrose, glucose, fructose and total soluble sugar by IAA were significantly higher than control, whereas these parameters were declined by TIBA. Exogenous TIBA resulted in accumulation of starch (unfavorable to sugar metabolism) and crude fiber contents (declined swollen gall quality). Additionally, it was firstly reported the stimulation of exogenously applied of IAA and TIBA on plant growth and hyphae growth of U. esculenta. Microscopic analyses revealed that abundant hyphae were well-distributed closely to cell wall after IAA treatment, which could produce endogenous plant hormones, promoting the swollen cell structure enlargement. And hyphal aggregation over-growth by TIBA treatment indicated the vigorously increase of hyphae was surpassed the plant self-growth. These changes were greatly contributed to the increase of endogenous IAA content. The utilization of exogenous IAA and TIBA in present study proved IAA played a dominant role in regulating Z. latifolia growth. [ABSTRACT FROM AUTHOR]

• In the late stage of mononuclear microspore, the tapetum of MS7-2 was abnormally expanded, resulting in the extrusion of microspores and the inability to undergo mitosis to form mature pollen grains, while the tapetum of MF7-2 degraded normally. • The differential expression of transcription factors related to anther and pollen development in MS7-2 may be related to anther abortion. • AHA9 and VHA-G3 related to ATP synthase were significantly down-regulated in MS7-2, which may lead to the formation of ROS by the combination of excess electrons and molecular oxygen. The accumulation of ROS in cells affected the PCD of tapetum. Male sterility is a complex developmental process involving the differentiation of different tissues and the coordinated expression of genes. It is not only used to produce hybrids with effective utilization of heterosis but also an ideal tool to study plant development networks. Here, we carried out morphological and cytological observations on the flower buds of the previously studied male-sterile mutant MS7-2 and its wild-type fertile plant MF7-2 at different developmental stages and performed transcriptomic and proteomic analyses. Compared with the anthers of MF7-2, the anthers of MS7-2 were obviously atrophied, the anther surface was concave, the tapetum was abnormally expanded at the mononuclear microspore stage and normal pollen grains could not be produced. Proteomic analysis showed that the differentially expressed proteins (DEPs) were mainly involved in lipid transport, lipid binding and lipase activity and were mainly concentrated in carbohydrate metabolism, biosynthesis of other secondary metabolites and lipid metabolism. Transcriptomic results showed that the differentially expressed genes (DEGs) were mainly related to cell membrane components and were significantly enriched in carbohydrate metabolism, lipid metabolism, membrane transport and other pathways. In addition, transcription factors involved in anther and pollen development were also found to be significantly down-regulated in MS7-2, such as AMS, bHLH66, bHLH69 and WRKY 34. Weighted gene coexpression network analysis (WGCNA) screened two key modules of anther abortion in wucai. The DEGs in the two modules were mainly enriched in the "terpenoid backbone biosynthesis," "pentose and glucuronate interconversions" and "cutin, suberine and wax biosynthesis" pathways, and three hub genes were screened as BraA02g028550.3C (LACS5), BraA01g016670.3C (VHA-G3) and BraA03g043400. 3C (AMS). Through transcriptomic and proteomic analyses, a regulatory network of MS7-2 male sterility of was constructed. It is speculated that the down-regulation of these genes and proteins in MS7-2 anthers inhibits the synthesis of some lipids and endogenous metabolites and accumulates a large amount of reactive oxygen species (ROS) in the tapetum, leading to the failure of normal PCD and the abortion of MS7-2. This study provides new insights into the molecular mechanism of male sterility in wucai. [ABSTRACT FROM AUTHOR]

Objectives: Complications during contraceptive implant removal are important for users and programs. We describe breakage rates during Sino-implant (II) removals at four Chinese family planning clinics.Study Design: We collected data by observation of consecutive removal cases and subsequent data transcription onto a standardized case report form. Three sites used the "pull out" removal technique, and one site used the "U" technique.Results: Sino-implant (II) rods were removed from 318 women. There were 16 implant breaks (5.0%), with the breakage rate varying by site from 0% to 7.4%. All 16 breaks occurred at the three sites that used the standard "pull out" technique. Six implants were cut by the scalpel, five were snapped by the clamp, and five were unspecified. Other contributing factors included deeper or wider positioning of the implants (n=6) and implants that were enveloped by thick fibrous tissue (n=3). There was no relationship between breakage rate and duration of implant use. Less than 1% of removals took more than 10 min.Conclusions: Both the standard "pull out" technique as well as the "U" technique can be used to remove Sino-implant (II). Breakage during implant removal may not be problematic if all fragments of the rod are readily removable. Breakage occurs with predictable low frequency, and training is needed to assure that providers can deal with breakage events.Implications: Contraceptive implant removal complications are important for users and programs. These are some of the first data on breakage during removal of Sino-implant (II). More than one removal technique can be used, but training is required to ensure that providers can deal with the infrequent implant breaks. [ABSTRACT FROM AUTHOR]

Objectives Complications during contraceptive implant removal are important for users and programs. We describe breakage rates during Sino-implant (II) removals at four Chinese family planning clinics. Study design We collected data by observation of consecutive removal cases and subsequent data transcription onto a standardized case report form. Three sites used the “pull out” removal technique, and one site used the “U” technique. Results Sino-implant (II) rods were removed from 318 women. There were 16 implant breaks (5.0%), with the breakage rate varying by site from 0% to 7.4%. All 16 breaks occurred at the three sites that used the standard “pull out” technique. Six implants were cut by the scalpel, five were snapped by the clamp, and five were unspecified. Other contributing factors included deeper or wider positioning of the implants ( n =6) and implants that were enveloped by thick fibrous tissue ( n =3). There was no relationship between breakage rate and duration of implant use. Less than 1% of removals took more than 10 min. Conclusions Both the standard “pull out” technique as well as the “U” technique can be used to remove Sino-implant (II). Breakage during implant removal may not be problematic if all fragments of the rod are readily removable. Breakage occurs with predictable low frequency, and training is needed to assure that providers can deal with breakage events. Implications Contraceptive implant removal complications are important for users and programs. These are some of the first data on breakage during removal of Sino-implant (II). More than one removal technique can be used, but training is required to ensure that providers can deal with the infrequent implant breaks. [ABSTRACT FROM AUTHOR]

This article has been retracted. Please see the Retraction Notice for more detail: https://doi.org/10.1186/s13287-019-1149-5. [ABSTRACT FROM AUTHOR]

Background: Brassinosteroids (BRs) have a positive effect on many processes during plant growth and development, and in response to various abiotic stressors. Low-temperature (LT) stress constricts the geographic distribution, growth, and development of wucai (Brassica campestris L. ssp. chinensis var. rosularis Tsen). However, there is little information on the global gene expression of BRs under LT stress in wucai. In this study, the molecular roles of 24-epibrassinolide (EBR) after exogenously application, were explored by RNA sequencing under LT conditions. Results: According to the Gene Ontology (GO) term and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses, photosynthesis was significantly enriched after spraying EBR under LT. The transcripts encoding the photosystem II (PSII) oxygen-evolving enhancer protein, photosystem I (PSI) subunit, light-harvesting chlorophyll protein complexes I and II, and ferredoxin were up-regulated after the application of EBR. Transcripts encoding several key enzymes involved in chlorophyll biosynthesis were also up-regulated, accompanied by significant differences in the contents of 5-aminolevulinic acid (ALA), porphobilinogen (PBG), protoporphyrin IX (Proto IX), Mg-protoporphyrin IX (Mg-proto IX), protochlorophyllide (Pchl), and photosynthetic pigments. Notably, transcriptional and physiological analyses revealed that under LT stress, plant responses to EBR involved a major reorientation of photosynthesis, as well as porphyrin and chlorophyll metabolism. Conclusion: This study explored the role of EBR as an LT stress tolerance mechanism in wucai. At the transcription level, LT tolerance manifests as an enhancement of photosynthesis, and the amelioration of porphyrin and chlorophyll metabolism. [ABSTRACT FROM AUTHOR]

Light is one of the most important abiotic factors for most plants, which affects almost all growth and development stages. In this study, physiological indicators suggest that the application of exogenous Ca2+ improves photosynthesis and changes phytohormone levels. Under weak light, photosynthetic parameters of the net photosynthetic rate (PN), stomatal conductance (Gs), and transpiration rate (Tr) decreased; the antioxidation systems peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) reduced; the degrees of malondialdehyde (MDA), H2O2, and superoxide anion (O2−) free radical damage increased; while exogenous Ca2+ treatment was significantly improved. RNA-seq analysis indicated that a total of 13,640 differently expressed genes (DEGs) were identified and 97 key DEGs related to hormone, photosynthesis, and calcium regulation were differently transcribed. Gene ontology (GO) terms and Kyoto encyclopedia of genes and genomes (KEGG) pathway analyses, plant hormone signal transduction, photosynthesis, carbon metabolism, and phenylpropanoid biosynthesis were significantly enriched. Additionally, quantitative real-time PCR (qRT-PCR) analysis confirmed some of the key gene functions in response to Ca2+. Overall, these results provide novel insights into the complexity of Ca2+ to relieve injuries under weak light, and they are helpful for potato cultivation under weak light stress. [ABSTRACT FROM AUTHOR]

The genotype WS-1, previously identified from novel wucai germplasm, is tolerant to both low-temperature (LT) and high-temperature (HT) stress. However, it is unclear which signal transduction pathway or acclimation mechanisms are involved in the temperature-stress response. In this study, we used the proteomic method of tandem mass tag (TMT) coupled with liquid chromatography-mass spectrometry (LC-MS/MS) to identify 1022 differentially expressed proteins (DEPs) common to WS-1, treated with either LT or HT. Among these 1022 DEPs, 172 were upregulated in response to both LT and HT, 324 were downregulated in response to both LT and HT, and 526 were upregulated in response to one temperature stress and downregulated in response to the other. To illustrate the common regulatory pathway in WS-1, 172 upregulated DEPs were further analyzed. The redox homeostasis, photosynthesis, carbohydrate metabolism, heat-shockprotein, and chaperones and signal transduction pathways were identified to be associated with temperature stress tolerance in wucai. In addition, 35S:BcccrGLU1 overexpressed in Arabidopsis, exhibited higher reduced glutathione (GSH) content and reduced glutathione/oxidized glutathione (GSH/GSSG) ratio and less oxidative damage under temperature stress. This result is consistent with the dynamic regulation of the relevant proteins involved in redox homeostasis. These data demonstrate that maintaining redox homeostasis is an important common regulatory pathway for tolerance to temperature stress in novel wucai germplasm. [ABSTRACT FROM AUTHOR]

Background: Exosomes are nanoscale membrane vesicles secreted by both normal and cancer cells, and cancer cell-derived exosomes play an important role in the cross-talk between cancer cells and other cellular components in the tumor microenvironment. Mesenchymal stem cells (MSCs) have tropism for tumors and have been used as tumor-tropic vectors for tumor therapy; however, the safety of such therapeutic use of MSCs is unknown. In this study, we investigated the role of glioma cell-derived exosomes in the tumor-like phenotype transformation of human bone marrow mesenchymal stem cells (hBMSCs) and explored the underlying molecular mechanisms. Methods: The effect of exosomes from U251 glioma cells on the growth of hBMSCs was evaluated with the CCK-8 assay, KI67 staining, and a cell cycle distribution assessment. The migration and invasion of hBMSCs were evaluated with a Transwell assay. A proteomics and bioinformatics approach, together with Western blotting and reverse transcriptase-polymerase chain reaction, was used to investigate the effect of U251 cell-derived exosomes on the proteome of hBMSCs. Results: U251 cell-derived exosomes induced a tumor-like phenotype in hBMSCs by enhancing their proliferation, migration, and invasion and altering the production of proteins involved in the regulation of the cell cycle. Moreover, U251 cell-derived exosomes promoted the production of the metastasis-related proteins MMP-2 and MMP-9, glioma marker GFAP, and CSC markers (CD133 and Nestin). The ten differentially expressed proteins identified participated in several biological processes and exhibited various molecular functions, mainly related to the inactivation of glycolysis. Western blotting showed that U251 cell-derived exosomes upregulated the levels of Glut-1, HK-2, and PKM-2, leading to the induction of glucose consumption and generation of lactate and ATP. Treatment with 2-deoxy-d-glucose significantly reversed these effects of U251 cell-derived exosomes on hBMSCs. Conclusions: Our data demonstrate that glioma cell-derived exosomes activate glycolysis in hBMSCs, resulting in their tumor-like phenotype transformation. This suggests that interfering with the interaction between exosomes and hBMSCs in the tumor microenvironment has potential as a therapeutic approach for glioma. ᅟ [ABSTRACT FROM AUTHOR]

Wucai is a biannual leafy vegetable that is more sensitive to cold than most Brassicaceae vegetables. Here, phenotypic differences in wucai were investigated to identify those genotypes with high cold tolerance at low temperature, which could allow their cultivation in cold climates. In all, on the basis of PIabs, 20 wucai genotypes (10 lower PIabs and 10 higher PIabs) were selected from a collection of 124 genotypes. Both W16-13 and SW-3 (higher PIabs) and the LS-6 and W15-16 (lower PIabs) were screened from the 20 wucai genotypes according to several key plant physiological traits: net photosynthetic rate, electrolyte leakage, chilling injury index, specific leaf area, malondialdehyde contents, and PIabs. To further verify the reliability of PIabs, four genotypes were grown under low temperature gradient conditions and their morphological indexes, chlorophyll content, total antioxidant capacity, fluorescence transients (OJIP transients), leaf cell ultrastructure, and gene expression were measured. These indicators strongly demonstrated that the W16-13 and SW-3, which had higher PIabs, possessed higher resistance to cold stress, while both LS-6 and W15-16 were sensitive to cold. As this study shows, the easily measured performance index, PIabs, could be applied to wucai genotypes to screen for one or more varieties characterized by higher cold tolerance. [ABSTRACT FROM AUTHOR]