Physiological and Transcriptomic Responses of Bok Choy to Heat Stress.

High temperatures have adverse effects on the yield and quality of vegetables. Bok choy, a popular vegetable, shows varying resistance to heat. However, the mechanism underlying the thermotolerance of bok choy remains unclear. In this study, 26 bok choy varieties were identified in screening as being heat-resistant at the seedling stage; at 43 °C, it was possible to observe obvious heat damage in different bok choy varieties. The physiological and biochemical reactions of a heat-tolerant cultivar, Jinmei (J7), and a heat-sensitive cultivar, Sanyueman (S16), were analyzed in terms of the growth index, peroxide, and photosynthetic parameters. The results show that Jinmei has lower relative conductivity, lower peroxide content, and higher total antioxidant capacity after heat stress. We performed transcriptome analysis of the two bok choy varieties under heat stress and normal temperatures. Under heat stress, some key genes involved in sulfur metabolism, glutathione metabolism, and the ribosome pathway were found to be significantly upregulated in the heat-tolerant cultivar. The key genes of each pathway were screened according to their fold-change values. In terms of sulfur metabolism, genes related to protease activity were significantly upregulated. Glutathione synthetase (GSH2) in the glutathione metabolism pathway and the L3e, L23, and S19 genes in the ribosomal pathway were significantly upregulated in heat-stressed cultivars. These results suggest that the total antioxidant capacity and heat injury repair capacity are higher in Jinmei than in the heat-sensitive variety, which might be related to the specific upregulation of genes in certain metabolic pathways after heat stress.

Exogenous spraying of IAA improved the efficiency of microspore embryogenesis in Wucai (Brassica campestris L.) by affecting the balance of endogenous hormones, energy metabolism, and cell wall degradation.

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.

Auxin participates in regulating the leaf curl development of Wucai (Brassica campestris L.).

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.

Combined Metabolome and Transcriptome Analysis Elucidates Sugar Accumulation in Wucai (Brassica campestris L.).

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 ß-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.

Identification of the BcLEA Gene Family and Functional Analysis of the BcLEA73 Gene in Wucai (Brassica campestris L.).

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.

Mapping and Validation of BrGOLDEN: A Dominant Gene Regulating Carotenoid Accumulation in Brassica rapa.

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.

Genome-wide analysis of the DREB family genes and functional identification of the involvement of BrDREB2B in abiotic stress in wucai (Brassica campestris L.).

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.

Heat stress response in Chinese cabbage (Brassica rapa L.) revealed by transcriptome and physiological analysis.

High temperatures have a serious impact on the quality and yield of cold-loving Chinese cabbage, which has evolved to have a unique set of stress mechanisms. To explore the relationship between these mechanisms and the heat-tolerance of Chinese cabbage, the physiological indicators of the heat-tolerant '268' line and heat-sensitive '334' line were measured. Under heat stress, the proline (Pro), soluble sugar (SS), and superoxide dismutase (SOD) indexes of the '268' line increased significantly. When additionally using transcriptome analysis, we found that the identified 3,360 DEGs were abundantly enriched in many metabolic pathways including 'plant hormone signal transduction', 'carbon metabolism', and 'glycolysis/gluconeogenesis'. Dynamic gene expression patterns showed that HKL1 in Cluster 15 may be a key factor in the regulation of sugar homeostasis. The interaction network screened four ABA-related genes in Cluster 15, suggesting that high temperatures lead to changes in hormonal signaling, especially an increase in ABA signaling. Compared with the '334' line, the expressions of Prx50, Prx52, Prx54, SOD1, and SOD2 in the '268' line were significantly upregulated, and these genes were actively involved in the reactive oxygen species (ROS) scavenging process. In summary, our results revealed the relationship between plant heat tolerance, physiology, and biochemistry and may also provide ideas for the future development of high-quality and heat-tolerant Chinese cabbage germplasm resources.

Transcriptome analysis and differential gene expression profiling of wucai (Brassica campestris L.) in response to cold stress.

BACKGROUND: Wucai suffers from low temperature during the growth period, resulting in a decline in yield and poor quality. But the molecular mechanisms of cold tolerance in wucai are still unclear. RESULTS: According to the phenotypes and physiological indexes, we screened out the cold-tolerant genotype "W18" (named CT) and cold-sensitive genotype "Sw-1" (named CS) in six wucai genotypes. We performed transcriptomic analysis using seedling leaves after 24 h of cold treatment. A total of 3536 and 3887 differentially expressed genes (DEGs) were identified between the low temperature (LT) and control (NT) comparative transcriptome in CT and CS, respectively, with 1690 DEGs specific to CT. The gene ontology (GO) analysis showed that the response to cadmium ion (GO:0,046,686), response to jasmonic acid (GO:0,009,753), and response to wounding (GO:0,009,611) were enriched in CT (LT vs NT). The DEGs were enriched in starch and sucrose metabolism and glutathione metabolism in both groups, and α-linolenic acid metabolism was enriched only in CT (LT vs NT). DEGs in these processes, including glutathione S-transferases (GSTs), 13S lipoxygenase (LOX), and jasmonate ZIM-domain (JAZ), as well as transcription factors (TFs), such as the ethylene-responsive transcription factor 53 (ERF53), basic helix-loop-helix 92 (bHLH92), WRKY53, and WRKY54.We hypothesize that these genes play important roles in the response to cold stress in this species. CONCLUSIONS: Our data for wucai is consistent with previous studies that suggest starch and sucrose metabolism increased the content of osmotic substances, and the glutathione metabolism pathway enhance the active oxygen scavenging. These two pathways may participated in response to cold stress. In addition, the activation of α-linolenic acid metabolism may promote the synthesis of methyl jasmonate (MeJA), which might also play a role in the cold tolerance of wucai.

TMT-based comparative proteomic analysis of the male-sterile mutant ms01 sheds light on sporopollenin production and pollen development in wucai (Brassica campestris L.).

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. SIGNIFICANCE: 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 H2O2 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.

Morphological characteristics and transcriptome analysis at different anther development stages of the male sterile mutant MS7-2 in Wucai (Brassica campestris L.).

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.

Comparative transcriptome analysis reveals that chlorophyll metabolism contributes to leaf color changes in wucai (Brassica campestris L.) in response to cold.

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.

Transcriptional profiling reveals changes in gene regulation and signaling transduction pathways during temperature stress in wucai (Brassica campestris L.).

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.

Characterization and transcriptomic analysis of a novel yellow-green leaf wucai (Brassica campestris L.) germplasm.

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.

Gene co-expression network analysis reveals key pathways and hub genes in Chinese cabbage (Brassica rapa L.) during vernalization.

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.

The effect of exogenous 24-epibrassinolide pretreatment on the quality, antioxidant capacity, and postharvest life of wucai (Brassica campestris L.).

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.

Transcriptome Analysis Reveals the Symbiotic Mechanism of Ustilago esculenta-Induced Gall Formation of Zizania latifolia.

Zizania latifolia is a perennial aquatic vegetable, whose symbiosis with the fungus Ustilago esculenta (member of Basidiomycota, class Ustilaginaceae) results in the establishment of swollen gall formations. Here, we analyzed symbiotic relations of Z. latifolia and U. esculenta, using a triadimefon (TDF) treatment and transcriptome sequencing (RNA-seq). Specifically, accurately identify the whole growth cycle of Z. latifolia. Microstructure observations showed that the presence of U. esculenta could be clearly observed after gall formation but was absent after the TDF treatment. A total of 17,541 differentially expressed genes (DEGs) were identified, based on the transcriptome. According to gene ontology term and Kyoto Encyclopedia of Genes and Genomes pathway results, plant hormone signal transduction, and cell wall-loosening factors were all significantly enriched due to U. esculenta infecting Z. latifolia; relative expression levels of hormone-related genes were identified, of which downregulation of indole 3-acetic acid (IAA)-related DEGs was most pronounced in JB_D versus JB_B. The ultra-high performance liquid chromatography analysis revealed that IAA, zeatin+trans zeatin riboside, and gibberellin 3 were increased under U. esculenta infection. Based on our results, we proposed a hormone-cell wall loosening model to study the symbiotic mechanism of gall formation after U. esculenta infects Z. latifolia. Our study thus provides a new perspective for studying the physiological and molecular mechanisms of U. esculenta infection of Z. latifolia causing swollen gall formations as well as a theoretical basis for enhancing future yields of cultivated Z. latifolia.[Formula: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CC0 "No Rights Reserved" license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law. 2021.

Genome-wide analysis of proline-rich extension-like receptor protein kinase (PERK) in Brassica rapa and its association with the pollen development.

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.

Comparative Transcriptome Analysis of Gene Expression and Regulatory Characteristics Associated with Different Vernalization Periods in Brassica rapa.

Brassica rapa is an important Chinese vegetable crop that is beneficial to human health. The primary factor affecting B. rapa yield is low temperature, which promotes bolting and flowering, thereby lowering its commercial value. However, quickened bolting and flowering can be used for rapid breeding. Therefore, studying the underlying molecular mechanism of vernalization in B.rapa is crucial for solving production-related problems. Here, the transcriptome of two B. rapa accessions were comprehensively analyzed during different vernalization periods. During vernalization, a total of 974,584,022 clean reads and 291.28 Gb of clean data were obtained. Compared to the reference genome of B. rapa, 44,799 known genes and 2280 new genes were identified. A self-organizing feature map analysis of 21,035 differentially expressed genes was screened in two B. rapa accessions, 'Jin Wawa' and 'Xiao Baojian'. The analysis indicated that transcripts related to the plant hormone signal transduction, starch and sucrose metabolism, photoperiod and circadian clock, and vernalization pathways changed notably at different vernalization periods. Moreover, different expression patterns of TPS, UGP, CDF, VIN1, and seven hormone pathway genes were observed during vernalization between the two accessions. The transcriptome results of this study provide a new perspective on the changes that occur during B. rapavernalization, as well as serve as an excellent reference for B. rapa breeding.