Phytotoxicity of nitrobenzene bioaccumulation in rice seedlings: Nitrobenzene inhibits growth, induces oxidative stress, and reduces photosynthetic pigment synthesis.

Nitrobenzene (NB) has been used in numerous industrial and agricultural fields as an organic compound intermediate. NB has mutagenicity and acute toxicity, and is typically a toxic pollutant in industrial wastewater worldwide. To evaluate its phytotoxicity, we treated rice (Oryza sativa) with different concentrations of NB (0, 5, 25, 50, 75, and 100 mg L-1). NB inhibited growth indices of rice (shoot and root length, fresh shoot and root weight, and dry shoot and root weight) as NB treatment concentrations increased. High concentrations (>25 mg L-1) of NB significantly inhibited rice root and shoot growth; root growth was more susceptible to NB. NB treatment could damage the structure and reduce the activity of rice seedling roots. The result of high performance liquid chromatography (HPLC) indicated that the bioaccumulation of NB in rice seedlings had a dose-dependent effect on the growth inhibition. NB reduced the photosynthetic pigment content and the expression levels of chlorophyll synthesis genes. NB treatment increased active oxygen radicals, electrical conductivity, malondialdehyde (MDA), proline, and soluble sugar contents. The expressions of antioxidant enzyme genes were induced by NB stress, and exhibited a phenomenon of initial increase followed by decrease. When the NB concentration was higher than 50 mg L-1, the gene expression levels decreased rapidly. This study provides insight into the association between exposure to NB and its phytotoxic effects on rice seedlings, and assesses the potential risk of NB bioaccumulation for crops that require a large amount of irrigation water.

Genome-wide identification of the myo-inositol oxygenase gene family in alfalfa (Medicago sativa L.) and expression analysis under abiotic stress.

Myo-inositol oxygenase (MIOX), a pivotal enzyme in the myo-inositol oxygenation pathway, catalyzes the cleavage of myo-inositol to UDP-glucuronic acid and plays a major role in plant adaptation to abiotic stress factors. However, studies pertaining to the MIOX gene family in alfalfa (Medicago sativa L.) are lacking. Therefore, this study characterized ten MsMIOX genes in the alfalfa genome. These genes were divisible into two classes distributed over three chromosomes and produced 12 pairs of fragment repeats and one pair of tandem repeats. Physicochemical properties, subcellular location, protein structure, conserved motifs, and gene structure pertinent to these MsMIOX genes were analyzed. Construction of a phylogenetic tree revealed that similar gene structures and conserved motifs were present in the same MsMIOX groups. Analysis of cis-acting elements revealed the presence of stress- and hormone-induced expression elements in the promoter regions of the MsMIOX genes. qRT-PCR analysis revealed that MsMIOX genes could be induced by various abiotic stress factors, such as salt, saline-alkali, drought, and cold. Under such conditions, MIOX activity in alfalfa was significantly increased. Heterologous MsMIOX2 expression in yeast enhanced salt, saline-alkali, drought, and cold tolerance. Overexpression of MsMIOX2 in the hairy roots of alfalfa decreased O2- and H2O2 content and enhanced the abiotic stress tolerance. This study offers comprehensive perspectives on the functional features of the MsMIOX family and provides a candidate gene for improving the abiotic stress tolerance of alfalfa.

Detecting SARS-CoV-2 in the Breath of COVID-19 Patients.

In the COVID-19 outbreak year 2020, a consensus was reached on the fact that SARS-CoV-2 spreads through aerosols. However, finding an efficient method to detect viruses in aerosols to monitor the risk of similar infections and enact effective control remains a great challenge. Our study aimed to build a swirling aerosol collection (SAC) device to collect viral particles in exhaled breath and subsequently detect SARS-CoV-2 using reverse transcription polymerase chain reaction (RT-PCR). Laboratory tests of the SAC device using aerosolized SARS-CoV-2 pseudovirus indicated that the SAC device can produce a positive result in only 10 s, with a collection distance to the source of 10 cm in a biosafety chamber, when the release rate of the pseudovirus source was 1,000,000 copies/h. Subsequent clinical trials of the device showed three positives and 14 negatives out of 27 patients in agreement with pharyngeal swabs, and 10 patients obtained opposite results, while no positive results were found in a healthy control group (n = 12). Based on standard curve calibration, several thousand viruses per minute were observed in the tested exhalations. Furthermore, referring to the average tidal volume data of adults, it was estimated that an exhaled SARS-CoV-2 concentration of approximately one copy/mL is detectable for COVID-19 patients. This study validates the original concept of breath detection of SARS-CoV-2 using SAC combined with RT-PCR.