Antimicrobial aromatic polyketides: a review of their antimicrobial properties and potential use in plant disease control

Aromatic polyketides are secondary metabolites widely found in bacteria, fungi, and plants, which are well-known for their diverse chemical structures and biological functions. The structural diversity of aromatic polyketides arises from a series of enzymatic modifications of the linear poly-β-ketone intermediates during biosynthesis. Their versatile bioactivities are exemplified by reports of their use as antibacterials, antifungals, antivirals, and antiparasitics. Despite many reports on the antimicrobial nature of aromatic polyketides, their potential use as plant disease control agents has still not been systematically explored and discussed. This review highlights examples of the use of aromatic polyketides as plant disease control agents and discusses their function and merits as agrochemicals.     

A systematic correlation analysis of carotenoids,chlorophyll, non-pigmented cell mass,and cell number for the blueprint of Dunaliella salina culture in a photobioreactor

Bioprocess and Biosystems Engineering - Microalgal carotenoids are attractive health ingredients, but their production should be optimized to improve cost-effectiveness. Understanding cellular...     

Structural and functional comparative mapping between the Brassica A genomes in allotetraploid Brassica napus and diploid Brassica rapa

Brassica napus (AACC genome) is an important oilseed crop that was formed by the fusion of the diploids B. rapa (AA) and B. oleracea (CC). The complete genomic sequence of the Brassica A genome will be available soon from the B. rapa genome sequencing project, but it is not clear how informative the A genome sequence in B. rapa (A(r)) will be for predicting the structure and function of the A subgenome in the allotetraploid Brassica species B. napus (A(n)). In this paper, we report the results of structural and functional comparative mapping between the A subgenomes of B. napus and B. rapa based on genetic maps that were anchored with bacterial artificial chromosomes (BACs)-sequence of B. rapa. We identified segmental conservation that represented by syntenic blocks in over one third of the A genome; meanwhile, comparative mapping of quantitative trait loci for seed quality traits identified a dozen homologous regions with conserved function in the A genome of the two species. However, several genomic rearrangement events, such as inversions, intra- and inter-chromosomal translocations, were also observed, covering totally at least 5% of the A genome, between allotetraploid B. napus and diploid B. rapa. Based on these results, the A genomes of B. rapa and B. napus are mostly functionally conserved, but caution will be necessary in applying the full sequence data from B. rapa to the B. napus as a result of genomic rearrangements in the A genome between the two species.     

Discrimination and Detection of Erwinia amylovora and Erwinia pyrifoliae with a Single Primer Set

Erwinia amylovora and Erwinia pyrifoliae cause fire blight and black-shoot blight, respectively, in apples and pears. E. pyrifoliae is less pathogenic and has a narrower host range than that of E. amylovora. Fire blight and black-shoot blight exhibit similar symptoms, making it difficult to distinguish one bacterial disease from the other. Molecular tools that differentiate fire blight from black-shoot blight could guide in the implementation of appropriate management strategies to control both diseases. In this study, a primer set was developed to detect and distinguish E. amylovora from E. pyrifoliae by conventional polymerase chain reaction (PCR). The primers produced amplicons of different sizes that were specific to each bacterial species. PCR products from E. amylovora and E. pyrifoliae cells at concentrations of 10⁴ cfu/ml and 10⁷ cfu/ml, respectively, were amplified, which demonstrated sufficient primer detection sensitivity. This primer set provides a simple molecular tool to distinguish between two types of bacterial diseases with similar symptoms.     

Clinicians’ Tendencies to Under-Rate Parkinsonian Tremors in the Less Affected Hand

The standard assessment method for tremor severity in Parkinson’s disease is visual observation by neurologists using clinical rating scales. This is, therefore, a subjective rating that is dependent on clinical expertise. The objective of this study was to report clinicians’ tendencies to under-rate Parkinsonian tremors in the less affected hand. This was observed through objective tremor measurement with accelerometers. Tremor amplitudes were measured objectively using tri-axis-accelerometers for both hands simultaneously in 53 patients with Parkinson’s disease during resting and postural tremors. The videotaped tremor was rated by neurologists using clinical rating scales. The tremor measured by accelerometer was compared with clinical ratings. Neurologists tended to under-rate the less affected hand in resting tremor when the contralateral hand had severe tremor in Session I. The participating neurologists corrected this tendency in Session II after being informed of it. The under-rating tendency was then repeated by other uninformed neurologists in Session III. Kappa statistics showed high inter-rater agreements and high agreements between estimated scores derived from the accelerometer signals and the mean Clinical Tremor Rating Scale evaluated in every session. Therefore, clinicians need to be aware of this under-rating tendency in visual inspection of the less affected hand in order to make accurate tremor severity assessments.     

Swine liver methylomes of Berkshire,Duroc and Landrace breeds by MeDIPS

Using a methyl‐DNA immunoprecipitation technique in combination with next‐generation deep sequencing, we conducted comprehensive DNA methylation profiling of liver genomes from three pig breeds: Berkshire, Duroc and Landrace. The profiles revealed that the distribution patterns of methylation signals along the genome are conserved among the three pig breeds. Specifically, many signals in coding genes were found in introns, and most signals in the repetitive elements were identified in non‐long terminal repeat (LTR) retrotransposons such as long and short interspersed repetitive elements, implying a significant association with alternative splicing and expression of retrotransposable elements respectively. Differentially methylated regions among the three pig breeds were identified in the non‐LTR retrotransposons, suggesting that they may lead to differential retrotransposable element activity. Altogether, this study provides advanced swine methylome data and valuable resources for understanding the function of DNA methylation in the evolutionary divergence of different pig breeds.     

4-1BB Signaling Breaks the Tolerance of Maternal CD8+ T Cells That Are Reactive with Alloantigens

4-1BB (CD137, TNFRSF9), a member of the activation-induced tumor necrosis factor receptor family, is a powerful T-cell costimulatory molecule. It generally enhances CD8⁺ T responses and even breaks the tolerance of CD8⁺ T cells in an antigen-specific manner. In the present study we found that it was expressed in the placentas of pregnant mice and that its expression coincided with that of the immunesuppressive enzyme indoleamine 2,3-dioxygenase (IDO). Therefore, we investigated whether 4-1BB signaling is involved in fetal rejection using agonistic anti-4-1BB mAb and 4-1BB-deficient mice. Treatment with agonistic anti-4-1BB mAb markedly increased the rate of rejection of allogeneic but not syngeneic fetuses, and this was primarily dependent on CD8⁺ T cells. Complement component 3 (C3) seemed to be the effector molecule because 4-1BB triggering resulting in accumulation of C3 in the placenta, and this accumulation was also reversed by anti-CD8 mAb treatment. These findings demonstrate that 4-1BB triggering breaks the tolerance of CD8⁺ T cells to alloantigens in the placenta. Moreover, triggering 4-1BB protected the pregnant mice from Listeria monocytogenes (LM) infection, but led to rejection of semi-allogeneic fetuses. Therefore, given the cross-recognition of alloantigen by pathogen-reactive CD8⁺ T cells, the true function of 4-1BB may be to reverse the hypo-responsiveness of pathogen-reactive CD8⁺ T cells in the placenta in cases of infection, even if that risks losing the fetus.     

Premature senescence in human breast cancer and colon cancer cells by tamoxifen-mediated reactive oxygen species generation

Aims

Cellular senescence is an important tumor suppression process in vivo. Tamoxifen is a well-known anti-breast cancer drug; however, its molecular function is poorly understood. Here, we examined whether tamoxifen promotes senescence in breast cancer and colon cancer cells for the first time.

Main methods

Human breast cancer MCF-7, T47D, and MDA-MB-435 and colorectal cancer HCT116 cells were treated with tamoxifen. Cellular senescence was measured by SA-β-gal staining and based on the protein expression of p53 and p21^Cip1/WAF1. The production of reactive oxygen species (ROS) was determined by staining with CM-H₂DCFDA and dihydroethidium (DHE). CK2 activity was assessed with a specific peptide substrate.

Key findings

Tamoxifen promoted senescence phenotype and ROS generation in MCF-7 and HCT116 cells. The ROS scavenger, N-acetyl-l-cysteine (NAC), and the NADPH oxidase inhibitor, apocynin, almost completely abolished this event. Tamoxifen inhibited the catalytic activity of CK2. Overexpression of CK2α antagonized senescence mediated by tamoxifen, indicating that tamoxifen induced senescence via a CK2-dependent pathway. A well-known CK2 inhibitor, 5,6-dichloro-1-β-d-ribofuranosylbenzimidazole (DRB), also stimulated ROS production and senescence in MCF-7 cells. Finally, experiments using T47D (wild-type p53) and MDA-MB-435 (mutant p53) cell lines suggested that tamoxifen induces p53-independent ROS production as well as p53-dependent senescence in breast cancer cells.

Significance

These results demonstrate that tamoxifen promotes senescence through a ROS–p53–p21^Cip1/WAF1 dependent pathway by inhibiting CK2 activity in breast cancer and colon cancer cells.