QTL mapping and candidate gene analysis reveal two major loci regulating green leaf color in non-heading Chinese cabbage.

KEY MESSAGE: Two major-effect QTL GlcA07.1 and GlcA09.1 for green leaf color were fine mapped into 170.25 kb and 191.41 kb intervals on chromosomes A07 and A09, respectively, and were validated by transcriptome analysis. Non-heading Chinese cabbage (NHCC) is a leafy vegetable with a wide range of green colors. Understanding the genetic mechanism behind broad spectrum of green may facilitate the breeding of high-quality NHCC. Here, we used F2 and F7:8 recombination inbred line (RIL) population from a cross between Wutacai (dark-green) and Erqing (lime-green) to undertake the genetic analysis and quantitative trait locus (QTL) mapping in NHCC. The genetic investigation of the F2 population revealed that the variation of green leaf color was controlled by two recessive genes. Six pigments associated with green leaf color, including total chlorophyll, chlorophyll a, chlorophyll b, total carotenoids, lutein, and carotene were quantified and applied for QTL mapping in the RIL population. A total of 7 QTL were detected across the whole genome. Among them, two major-effect QTL were mapped on chromosomes A07 (GlcA07.1) and A09 (GlcA09.1) corresponding to two QTL identified in the F2 population. The QTL GlcA07.1 and GlcA09.1 were further fine mapped into 170.25 kb and 191.41 kb genomic regions, respectively. By comparing gene expression level and gene annotation, BraC07g023810 and BraC07g023970 were proposed as the best candidates for GlcA07.1, while BraC09g052220 and BraC09g052270 were suggested for GlcA09.1. Two InDel molecular markers (GlcA07.1-BcGUN4 and GlcA09.1-BcSG1) associated with BraC07gA023810 and BraC09g052220 were developed and could effectively identify leaf color in natural NHCC accessions, suggesting their potential for marker-assisted leaf color selection in NHCC breeding.

Potential Regulatory Networks and Heterosis for Flavonoid and Terpenoid Contents in Pak Choi: Metabolomic and Transcriptome Analyses.

Pak choi exhibits a diverse color range and serves as a rich source of flavonoids and terpenoids. However, the mechanisms underlying the heterosis and coordinated regulation of these compounds-particularly isorhamnetin-remain unclear. This study involved three hybrid combinations and the detection of 528 metabolites from all combinations, including 26 flavonoids and 88 terpenoids, through untargeted metabolomics. Analysis of differential metabolites indicated that the heterosis for the flavonoid and terpenoid contents was parent-dependent, and positive heterosis was observed for isorhamnetin in the two hybrid combinations (SZQ, 002 and HMG, ZMG). Moreover, there was a high transcription level of flavone 3'-O-methyltransferase, which is involved in isorhamnetin biosynthesis. The third group was considered the ideal hybrid combination for investigating the heterosis of flavonoid and terpenoid contents. Transcriptome analysis identified a total of 12,652 DEGs (TPM > 1) in various groups that were used for comparison, and DEGs encoding enzymes involved in various categories, including "carotenoid bio-synthesis" and "anthocyanin biosynthesis", were enriched in the hybrid combination (SZQ, 002). Moreover, the category of anthocyanin biosynthesis also was enriched in the hybrid combination (HMG, ZMG). The flavonoid pathway demonstrated more differential metabolites than the terpenoid pathway did. The WGCNA demonstrated notable positive correlations between the dark-green modules and many flavonoids and terpenoids. Moreover, there were 23 ERF genes in the co-expression network (r ≥ 0.90 and p < 0.05). Thus, ERF genes may play a significant role in regulating flavonoid and terpenoid biosynthesis. These findings enhance our understanding of the heterosis and coordinated regulation of flavonoid and terpenoid biosynthesis in pak choi, offering insights for genomics-based breeding improvements.

Transcriptome sequencing and gas chromatography-mass spectrometry analyses provide insights into ß-caryophyllene biosynthesis in Brassica campestris.

Sesquiterpenes are important defensive secondary metabolites and aroma components. However, limited information is available on the mechanism of sesquiterpene formation and composition in the non-heading Chinese cabbage (NHCC) leaf. Therefore, headspace solid-phase microextraction/gas chromatography-mass spectrometry (HS-SPME/GC-MS) combined with transcriptome analysis was used to study the mechanism of volatile organic compound formation. A total of 26 volatile organic compounds were identified in two NHCC cultivars 'SZQ' and 'XQC' and their F1 hybrids. Among these, sesquiterpene ß-caryophyllene was identified only in 'XQC' and F1. Five genes encoding caryophyllene synthase were identified. The candidate ß-caryophyllene synthase genes BcTPSa11 and BcTPSa21 had high expression levels only in 'XQC' and F1. In addition, several transcription factors of MYB-related, MYB, bHLH, and AP2/ERF families were identified by co-expression, suggesting that they regulate ß-caryophyllene biosynthesis. Our results provide a molecular basis for sesquiterpene biosynthesis as well as insights into the regulatory network of ß-caryophyllene in NHCC.

Investigation Into Environmental Selenium and Arsenic Levels and Arseniasis Prevalence in an Arsenic-Affected Coal-Burning Area.

This study aims to explore whether selenium (Se) concentration correlates with arseniasis in a high-arsenic coal area in the southern Shaanxi Province, China. Herein, an epidemiological investigation was conducted among 100 arsenic (As)-poisoned patients in Ziyang County, an area with high soil As and Se levels. Fifty healthy subjects were selected from areas without endemic As poisoning. The subjects in the high-As coal area were diagnosed with either normal, suspicious, mild, moderate, or severe As poisoning. Local coal, water, soil, corn, and pepper samples, as well as hair, blood, and urine samples of subjects and patients were collected and analyzed for their As and Se contents. The contents of As and Se in coal, soil, corn, pepper, and hair samples from Ziyang County were significantly higher than those in the control area. The As content of hair in Ziyang County positively correlated with As poisoning, whereas the Se content of hair and urine negatively correlated with As poisoning. The Se content in the body was negatively correlated with the degree of As poisoning, indicating that Se may accelerate the metabolism and decumulation of As and antagonize As toxicity.

BcGR1.1, a Cytoplasmic Localized Glutathione Reductase, Enhanced Tolerance to Copper Stress in Arabidopsis thaliana.

Copper is a mineral element, which is necessary for the normal growth and development of plants, but high levels of copper will seriously damage plants. Studies have shown that AtGR1 improves the tolerance of Arabidopsis to aluminum and cadmium stress. However, the role of GR in the copper stress response of plants is still unclear. Here, we identified four genes (named BcGR1.1, BcGR1.2, BcGR2.1 and BcGR2.2, respectively) encoding glutathione reductase (GR) in non-heading Chinese cabbage (Brassica campestris (syn. Brassica rapa) ssp. chinensis), which could be divided into two types based on the subcellular localization. Among them, BcGR1.1, which belonged to the cytoplasmic localization type, was significantly upregulated under copper stress. Compared to WT (the wild type), Arabidopsis thaliana heterologously overexpressed BcGR1.1 had longer roots, higher fresh weight, higher GSH levels and GSH/GSSG (oxidized form of GSH) ratio, and accumulated more superoxide dismutase and peroxidase under copper stress. However, in the AsA-GSH cycle under copper stress, the contents of AsA and AsA/DHA were significantly downregulated, and the contents of DHA and T-AsA (total AsA) were upregulated, in the BcGR1.1-overexpressing Arabidopsis. Therefore, BcGR1.1 could improve the scavenging ability of reactive oxygen species (ROS) by increasing the activity of GR, antioxidant enzymes and the utilization of AsA, and then enhance the copper stress tolerance of plants.

[Contrast analysis on two air fluorine content measurement methods].

OBJECTIVE: To take the two kinds of sampling and measurement methods of air fluorine content in the endemic fluorosis area to carry on the comparison, understanding their difference and inside relation. METHODS: Sampled 22 households random on the scene in the disease area with two samplers by two methods, at the position of which, at the same time, equidistance, same highness, as close as possible, but not produce interactive effect, to collect 34 of the air sample, and then gained the results by their respective methods of laboratory analysis and statistical analysis. RESULTS: The test of significance between two methods was P > 0.05, the coefficient of correlation was r = 0.7752, the test of significance was P < 0.01, the equation of linear regression between the GB method (X) and the manual method (Y) was Y = 1.1623X + 0.0008, the test of significance of coefficient of regression was P < 0.01. CONCLUSION: Two kinds of methods had no significant differences. They preset the medium degree positive correlation and a linear regression. The air fluoride in different granularity of suspended particles was not the same. The GB method was more applicable to research of synthesis damage towards the exposing crowd in burning coal fluorine, and manual method was more applicable to research of the damage resulting from the exposing crowd in burning coal fluorine through the breath system. Generally speaking, the results of the manual method was higher than the GB method.

[Pilot experiment of fluorine fixing ratio of coated lump stone coal fuel].

The pilot experiment on coated lump stone coal fuel selected from 16 families in Haoping Shanxi were studied. 8 families burned coating high fluorine lump stone coal with lime, clay and low fluorine anthracite, 8 families burned untreated lump stone coal. The results show that the fluorine-fixing ratio at treated group was 75.0% when coal fluorine compared with coal cinder fluorine. In comparison with untreated group, the concentration of door air fluoride lowered 85.7%, SO2 lowered 75.0%, dust lowered 55.3%.

[Regularity of flourine release from fluorine-rich coal combustion in the fluorine poisoning area].

Laboratory experiments and in situ measurements inside farmer's houses indicate that the fluorine concentration of indoor air was positively related with the fluorine content in the consumed coal (R = 0.612, P<0.01), but fluorine content in the coal had no effect on the release rate of coal fluorine under the usual combustion temperature of about 1000 degrees C. The release rate of coal fluorine varied versus combustion temperature ranging from 200 to 1200 degrees C, following a "S" curve pattern, increasing slowly under 300 to 700 degrees C, but quickly under 700 to 1000 degrees C, and then slowly again before finally reaching 100% under 1100 to 1200 degrees C, this curve can be fit by Logistic equation. The release rate of coal fluorine usually depends upon the existence status of fluorine and the chemical and mineral components of the coal. The fluorine in soft coal or anthracite from Guizhou is released more quickly than in bone coal from Southern Shanxi, with the former almost completely released under 1100 degrees C but the later almost completely released under 1200 degrees C. The combustion temperature of civil stoves is at most 1000 degrees C, under which averagely 86.9% of the fluorine in coal from Guizhou and 80.6% of that in bone coal from Southern Shanxi is released.