Effects of plant morphology, vitamin C, and other co-present pesticides on the deposition, dissipation, and metabolism of chlorothalonil in pakchoi.

Pesticide residues have been a focus of attention of food safety. Different varietal pakchoi plants grown in open fields were studied to understand effects of morphology, leaf wax content, and vitamin C on the deposition, dissipation, and metabolism of chlorothalonil. The loose pakchoi plants and flat leaves were conducive to pesticide deposition, but not plants with erect leaves. Chlorothalonil on nine varieties of pakchoi dissipated in the first-order kinetic with T1/2 s of 1.4 ~ 2.0 days. Vitamin C in pakchoi could promote the dissipation of chlorothalonil. Carbendazim could significantly promote the dissipation of chlorothalonil on pakchoi. Interestingly, four metabolites of chlorothalonil were identified in the pakchoi and the metabolic pathway was predicted by DFT calculations. The risk assessment showed that pakchoi were safe for consumption after 10 days of application of the recommended dose. This work provides important information for the understanding of deposition, dissipation, and metabolism of chlorothalonil in pakchoi.

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.

Study of target spacing of thermo-sensitive carrier on the activity recovery of immobilized penicillin G acylase.

The immobilized penicillin G acylase (PGA) is an important industrial catalyst, the activity recovery rate of it directly affects enterprise efficiency. How to improve the enzyme activity recovery rate has been a research focus in this field. Based on the above problems, this work further improved the activity recovery rate by adjusting the target spacing for the first time. Glycidyl methacrylate (GMA) was used as the immobilized target and methyl methacrylate (MMA) as the copolymer monomer. According to the copolymer composition equation of P(MMA-co-GMA), the thermo-sensitive copolymers, PDEA-b-PHEMA-b-P(MMA-co-GMA) with different target spacings, were synthesized rapidly and efficiently via reversible addition-fragmentation chain transfer (RAFT) polymerization method. The error range between the theoretical and actual values of MMA and GMA in the copolymers carrier was (0-4)%, which demonstrated that the reliability of using composition equation to accurately and quickly synthesize copolymers with specific spacing. Studies on the thermo-sensitive showed that the low critical solution temperature (LCST) of the copolymer carrier decreased with the increase of hydrophobic monomer. Most importantly, the activity recovery rate increased with the increase of target spacing, and when the molar ratio of MMA to GMA in the copolymer was 8.75:1, the recovery of activity of immobilized PGA could be up to 63.50%, which was 21.70% higher than that of pure GMA. This work provided an important idea for improving the activity of immobilized PGA.