Genome Sequence of a Nicotine-Degrading Strain of Arthrobacter

We announce a 4.63-Mb genome assembly of an isolated bacterium that is the first sequenced nicotine-degrading Arthrobacter strain. Nicotine catabolism genes of the nicotine-degrading plasmid pAO1 were predicted, but plasmid function genes were not found. These results will help to better illustrate the molecular mechanism of nicotine degradation by Arthrobacter.     

Xanthomonas campestris sensor kinase HpaS co-opts the orphan response regulator VemR to form a branched two-component system that regulates motility

Xanthomonas campestris pv. campestris (Xcc) controls virulence and plant infection mechanisms via the activity of the sensor kinase and response regulator pair HpaS/hypersensitive response and pathogenicity G (HrpG). Detailed analysis of the regulatory role of HpaS has suggested the occurrence of further regulators besides HrpG. Here we used in vitro and in vivo approaches to identify the orphan response regulator VemR as another partner of HpaS and to characterize relevant interactions between components of this signalling system. Bacterial two-hybrid and protein pull-down assays revealed that HpaS physically interacts with VemR. Phos-tag SDS-PAGE analysis showed that mutation in hpaS reduced markedly the phosphorylation of VemR in vivo. Mutation analysis reveals that HpaS and VemR contribute to the regulation of motility and this relationship appears to be epistatic. Additionally, we show that VemR control of Xcc motility is due in part to its ability to interact and bind to the flagellum rotor protein FliM. Taken together, the findings describe the unrecognized regulatory role of sensor kinase HpaS and orphan response regulator VemR in the control of motility in Xcc and contribute to the understanding of the complex regulatory mechanisms used by Xcc during plant infection.     

Testosterone Affects Neural Gene Expression Differently in Male and Female Juncos: A Role for Hormones in Mediating Sexual Dimorphism and Conflict

Despite sharing much of their genomes, males and females are often highly dimorphic, reflecting at least in part the resolution of sexual conflict in response to sexually antagonistic selection. Sexual dimorphism arises owing to sex differences in gene expression, and steroid hormones are often invoked as a proximate cause of sexual dimorphism. Experimental elevation of androgens can modify behavior, physiology, and gene expression, but knowledge of the role of hormones remains incomplete, including how the sexes differ in gene expression in response to hormones. We addressed these questions in a bird species with a long history of behavioral endocrinological and ecological study, the dark-eyed junco (Junco hyemalis), using a custom microarray. Focusing on two brain regions involved in sexually dimorphic behavior and regulation of hormone secretion, we identified 651 genes that differed in expression by sex in medial amygdala and 611 in hypothalamus. Additionally, we treated individuals of each sex with testosterone implants and identified many genes that may be related to previously identified phenotypic effects of testosterone treatment. Some of these genes relate to previously identified effects of testosterone-treatment and suggest that the multiple effects of testosterone may be mediated by modifying the expression of a small number of genes. Notably, testosterone-treatment tended to alter expression of different genes in each sex: only 4 of the 527 genes identified as significant in one sex or the other were significantly differentially expressed in both sexes. Hormonally regulated gene expression is a key mechanism underlying sexual dimorphism, and our study identifies specific genes that may mediate some of these processes.     

Phosphorylation of the septin cdc3 in g1 by the cdc28 kinase is essential for efficient septin ring disassembly

The septins constitute a family of filament-forming proteins ubiquitous in eukaryotic species. We demonstrate here that the Saccharomyces cerevisiae septin, Cdc3, is a substrate of the cell cycle regulatory cyclin-dependent kinase (Cdk), Cdc28. Two serines near the C-terminus of Cdc3 are phosphorylated in a Cdc28-dependent manner. Analysis of a mutant allele that cannot be phosphorylated at these sites revealed an effect of Cdc28 phosphorylation of Cdc3 at the time of budding. Immunofluorescence analysis of wild-type and mutant Cdc3 indicated that prevention of phosphorylation at Cdc28-dependent sites impairs the disassembly of the old septin ring, which is inherited at mitosis but which usually disappears immediately prior to assembly of a new ring. Furthermore, immuno-fluorescence analysis of septin ring dynamics in a G1 cyclin (Cln) mutant suggests that G1 cyclin function is required for efficient ring disassembly. Thus, phosphorylation of Cdc3 by the Cdc28 kinase at the end of G1 may facilitate initiation of a new cell cycle by promoting disassembly of the obsolete septin ring from the previous cell cycle.     

The use of SARS-CoV-2-related coronaviruses from bats and pangolins to polarize mutations in SARS-Cov-2

正Dear Editor,The coronavirus disease 2019 (COVID-19) caused by the SARS-CoV-2 coronavirus has become a global pandemic.The SARS-CoV-2 genome has a similarity of 96.2%to that of RaTG13, a bat SARS-CoV-2-related coronavirus detected in Rhinolophus affinis (Paraskevis et al., 2020; Zhou et al.,2020). The SARS-CoV-2 genome also has 85.5%-92.4%     

Molecular Mechanism of Nicotine Degradation by a Newly Isolated Strain,Ochrobactrum sp. Strain SJY1

A newly isolated strain, SJY1, identified as Ochrobactrum sp., utilizes nicotine as a sole source of carbon, nitrogen, and energy. Strain SJY1 could efficiently degrade nicotine via a variant of the pyridine and pyrrolidine pathways (the VPP pathway), which highlights bacterial metabolic diversity in relation to nicotine degradation. A 97-kbp DNA fragment containing six nicotine degradation-related genes was obtained by gap closing from the genome sequence of strain SJY1. Three genes, designated vppB, vppD, and vppE, in the VPP pathway were cloned and heterologously expressed, and the related proteins were characterized. The vppB gene encodes a flavin-containing amine oxidase converting 6-hydroxynicotine to 6-hydroxy-N-methylmyosmine. Although VppB specifically catalyzes the dehydrogenation of 6-hydroxynicotine rather than nicotine, it shares higher amino acid sequence identity with nicotine oxidase (38%) from the pyrrolidine pathway than with its isoenzyme (6-hydroxy-l-nicotine oxidase, 24%) from the pyridine pathway. The vppD gene encodes an NADH-dependent flavin-containing monooxygenase, which catalyzes the hydroxylation of 6-hydroxy-3-succinoylpyridine to 2,5-dihydroxypyridine. VppD shows 62% amino acid sequence identity with the hydroxylase (HspB) from Pseudomonas putida strain S16, whereas the specific activity of VppD is ∼10-fold higher than that of HspB. VppE is responsible for the transformation of 2,5-dihydroxypyridine. Sequence alignment and phylogenetic analysis suggested that the VPP pathway, which evolved independently from nicotinic acid degradation, might have a closer relationship with the pyrrolidine pathway. The proteins and functional pathway identified here provide a sound basis for future studies aimed at a better understanding of molecular principles of nicotine degradation.     

In vivo antitumour activity of amphiphilic silicon(IV) phthalocyanine with axially ligated rhodamine B

We explore the possible cellular cytotoxic activity of an amphiphilic silicon(IV) phthalocyanine with axially ligated rhodamine B under ambient light experimental environment as well as its in vivo antitumour potential using Hep3B hepatoma cell model. After loading into the Hep3B hepatoma cells, induction of cellular cytotoxicity and cell cycle arrest were detected. Strong growth inhibition of tumour xenograft together with significant tumour necrosis and limited toxicological effects exerted on the nude mice could be identified.     

Trace detection of picloram using an electrochemical immunosensor based on three-dimensional gold nanoclusters

Picloram, a herbicide widely used for broadleaf weed control, is persistent and mobile in soil and water with adverse health and environmental effects. It is important to develop a sensitive method for accurate detection of trace picloram in the environment. In this article, a type of ordered three-dimensional (3D) gold (Au) nanoclusters obtained by two-step electrodeposition using the spatial obstruction/direction of the polycarbonate membrane is reported. Bovine serum albumin (BSA)-picloram was immobilized on the 3D Au nanoclusters by self-assembly, and then competitive immunoreaction with picloram antibody and target picloram was executed. The horseradish peroxidase (HRP)-labeled secondary antibody was applied for enzyme-amplified amperometric measurement. The electrodeposited Au nanoclusters built direct electrical contact and immobilization interface with protein molecules without postmodification and positioning. Under the optimal conditions, the linear range for picloram determination was 0.001-10 μg/ml with a correlation coefficient of 0.996. The detection and quantification limits were 5.0 × 10⁻⁴ and 0.0021 μg/ml, respectively. Picloram concentrations in peach and excess sludge supernatant extracts were tested by the proposed immunosensor, which exhibited good precision, sensitivity, selectivity, and storage stability.