Melatonin-induced myeloblastosis viral oncogene homologs alleviate fresh-cut lotus root browning during storage by attenuating flavonoid biosynthesis and reactive oxygen species.

BACKGROUND: Lotus roots (Nelumbo nucifera Gaertn.) are rich in nutrients and have ornamental and food value. However, browning has caused huge economic losses and security risks during the storage and harvesting of fresh-cut lotus. This study investigated the role of melatonin in inhibiting lotus browning, and illustrates its molecular mechanism. RESULTS: The application of melatonin effectively retarded the process of lotus browning, enhanced reactive oxygen species (ROS) scavenging enzyme activity, and inhibited the activity of polyphenol oxidase (PPO), and peroxidase (POD). Melatonin reduced flavonoid content, and decreased enzymatic activity in flavonoid biosynthesis. Transcriptome Sequencing (RNA-seq) was used to screen the genes regulated by exogenous melatonin when defending against fresh-cut lotus browning. Gene co-expression analysis (GCN) indicated that the transcription factors MYB5, MYB6, and MYB308, activated by melatonin, were negatively related to the expression of PPO and the genes related to flavonoid and phenylpropanoid biosynthesis. These myeloblastosis viral oncogene homologs (MYBs) were positively related to the expression of genes encoding the enzymes in glutathione metabolism. CONCLUSION: Melatonin retarded lotus browning by transcriptional suppression of key genes associated with flavonoid and phenylpropanoid biosynthesis through the stimulation of MYB5, MYB6, and MYB308. © 2023 Society of Chemical Industry.

The Bioaccumulation and Tissue Distribution of Arsenic Species in Tilapia.

Arsenic is a public concern due to its widespread occurrence and carcinogenicity. Consumption of arsenic-contaminated fish is an important exposure pathway for human health. This study focused on understanding how exposure to arsenic-contaminated fish is informative to human health risk assessment. While the bioaccumulation and tissue distributions of total arsenic concentration in fish are commonly reported, there are limited studies related to the time-course of arsenic species in various tissues. Using the Tilapia as a case, this study aimed to investigate the bioaccumulation and tissue distributions (liver, gastrointestinal (GI), muscle, and gill) of arsenic species in freshwater fish via diet-borne inorganic arsenic exposure. In particular, the Tilapia were exposed to arsenic (III) and As(V) for 32 days. The accumulation of arsenic in all tissues linearly increased with time in the first 10 days' exposure, while the arsenic levels remained stable in the following 20 days' exposure. The accumulation of arsenic in tissue followed the sequence of intestine > liver > gill > muscle. Meanwhile, more than 90% of arsenic was converted into organic form in liver, gill, and muscle, while organic arsenic contributed about 30⁻80% to the total arsenic in the GI. The percentage of organic form in muscle is the highest, followed by gill, liver, and intestine, and arsenobetaine is the main form of organic arsenic. While the exposure profiles of As(III) and As(V) are quite similar, the absorption rate of As(V) is relatively higher than that of As(III). Information provided here can be instrumental for exposure assessment and risk management for arsenic in aquatic environment.

Effects of LaCoO3 perovskite nanoparticle on Daphnia magna: accumulation, distribution and biomarker responses.

Perovskite nanomaterials (PNMs) have been shown to be promising materials for the effective replacement of conventional energy source materials. With the increasing use of PNMs, they will inevitably enter aquatic environments, giving rise to concerns regarding the environmental impact of PNMs. To fill up the gap in information about the environmental effect of PNMs, Daphnia magna was exposed to a typical PNM LaCoO3 for 48 h, to assess temporal patterns in PNM bioaccumulation and distribution. Synchrotron radiation based micro X-ray fluorescence spectroscopy (µ-XRF) was used to investigate the time dependent spatial distribution of LaCoO3. Reactive oxygen species (ROS), superoxide dismutase (SOD) and Na+/K+-adenosine triphosphatase (ATPase) were measured as key biomarkers. The results showed that oxidative stress was observed at both LaCoO3 concentrations and Na+/K+-ATPase was inhibited by high levels of LaCoO3. The mode of action of LaCoO3 was mainly dependent on the metal forms. At low LaCoO3 levels, food ingestion was the main entry pathway into organisms and LaCoO3 nanoparticle aggregates accumulated in the gut area. At high LaCoO3 levels, both waterborne and dietary uptake was observed and the gut and thoracic limbs were the main target sites for LaCoO3 nanoparticle aggregates and dissolved ions, respectively. LaCoO3 was not found to translocate in daphnids during the 48 h exposure period at either concentration, suggesting that internalization did not occur. These findings help further our understanding of the fate of PNMs in aquatic organisms, as well as the associated biological responses to PNM exposure.