Reciprocal chromosome translocation associated with TDNA-insertion mutation in Arabidopsis: genetic and cytological analyses of consequences for gametophyte development and for construction of doubly mutant lines

Chromosomal rearrangements may complicate construction of Arabidopsis with multiple TDNA-insertion mutations. Here, crossing two lines homozygous for insertions in AtREV3 and AtPOLH (chromosomes I and V, respectively) and selfing F1 plants yielded non-Mendelian F2 genotype distributions: frequencies of +/++/+ and 1/1 2/2 progeny were only 0.42 and 0.25%. However, the normal development and fertility of double mutants showed AtPOLH-1 and AtREV3-2 gametes and 1/1 2/2 embryos to be fully viable. F2 distributions could be quantitatively predicted by assuming that F1 selfing produced inviable (1,2) and (+,+) gametophytes 86% of the time. Some defect intrinsic to the F1 selfing process itself thus appeared responsible. In selfing AtREV3 ^+/2 single mutants, imaging of ovules and pollen showed arrest or abortion, respectively, of half of gametophytes; however, gametogenesis was normal in AtREV3 ^2/2 homozygotes. These findings, taken together, suggested that T-DNA insertion at AtREV3 on chromosome I had caused a reciprocal I–V translocation. Spreads of meiosis I chromosomes in selfing AtREV3 ^+/2 heterozygotes revealed the predicted cruciform four-chromosome structures, which fluorescence in situ hybridization showed to invariably include both translocated and normal chromosomes I and V. Sequencing of the two junctions of T-DNA with AtREV3 DNA and the two with gene At5g59920 suggested translocation via homologous recombination between independent inverted-repeat T-DNA insertions. Thus, when crosses between TDNA-insertion mutants yield anomalous progeny distributions, TDNA-linked translocations should be considered. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Morphogenetic effects of 9-cis-retinoic acid on the regenerating limbs of the axolotl

9-cis-retinoic acid has recently been found to be a high affinity ligand for the retinoic X receptor (RXR). RXRs are believed to be involved in metabolic activities rather than in morphogenetic ones. Interestingly, RXR has been found to form heterodimers involving other receptors from the steroid family, such as the thyroid hormone receptor, vitamin D receptor or retinoic acid receptors (RARs). In this paper we examined whether or not 9-cis-retinoic acid had any morphogenetic properties on the regenerating axolotl limb. It is shown that 9-cis-retinoic acid proximalized regenerating limbs and was somewhat more potent in this action than all-trans-retinoic acid. Based on these observations, the possible roles of other receptors during pattern formation is discussed. Correspondence to: P.A. Tsonis     

Front Cover: Implantable self‐aligning fiber‐optic optomechanical devices for in vivo intraocular pressure‐sensing in artificial cornea

This work addresses an unmet clinical need, that of glaucoma monitoring through intraocular pressure (IOP) interrogation in patients with artificial corneas (keratoprost hesis). We demonstrate direct integration of a low‐drift, fiber‐optic Fabry‐Perot pressure sensor embedded in the keratoprosthesis via rapid, non‐contact micromagnetic fiber alignment. IOP interrogation is achieved by using white‐light interferometry, which provides sub‐mmHg IOP sensitivity. Further details can be found in the article by Pui‐Chuen Hui, Katia Shtyrkova, Chengxin Zhou, et al. ( e202000031 ).

     

Athletic humans and horses: Comparative analysis of interleukin-6 (IL-6) and IL-6 receptor (IL-6R) expression in peripheral blood mononuclear cells in trained and untrained subjects at rest

Background  

Horses and humans share a natural proclivity for athletic performance. In this respect, horses can be considered a reference species in studies designed to optimize physical training and disease prevention. In both species, interleukin-6 (IL-6) plays a major role in regulating the inflammatory process induced during exercise as part of an integrated metabolic regulatory network. The aim of this study was to compare IL-6 and IL-6 receptor (IL-6R) mRNA expression in peripheral blood mononuclear cells (PBMCs) in trained and untrained humans and horses.     

Evaluation of Extracts Produced by Some Tropical Fungi as Potential Cholinesterase Inhibitors

Summary Extracts of culture filtrates of fungal taxa belonging to Chaetomium sp., Guignardia mangiferae, Pestalotiopsis guepinii, Phomopsis sp., Physalospora sp., Xylaria sp., and sterile mycelium isolated as endophytes from leaves of members of the plant families Anacardiaceae, Apocynaceae, Leguminosae and Palmae; and seven different species of Penicillium isolated from insects were tested for their in vitro acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitory activity using Ellman’s colorimetric method adapted for thin layer chromatography. The results showed high rate of cholinesterase inhibitory activity, with the best result being obtained with Penicillium extracts, indicating that they might represent a valuable source for pharmaceutical applications and are worthy of further study.     

Alpha-Linolenic Acid Treatment Reduces the Contusion and Prevents the Development of Anxiety-Like Behavior Induced by a Mild Traumatic Brain Injury in Rats

Approximately, 1.7 million Americans suffer a TBI annually and TBI is a major cause of death and disability. The majority of the TBI cases are of the mild type and while most patients recover completely from mild TBI (mTBI) about 10% result in persistent symptoms and some result in lifelong disability. Anxiety disorders are the second most common diagnosis post-TBI. Of note, TBI-induced anxiety disorders are difficult to treat and remain a chronic condition suggesting that new therapies are needed. Previous work from our laboratory demonstrated that a mild TBI induced an anxiety-like phenotype, a key feature of the human condition, associated with loss of GABAergic interneurons and hyperexcitability in the basolateral amygdala (BLA) in rodents 7 and 30 days after a controlled cortical impact (CCI) injury. We now confirm that animals display significantly increased anxiety-like behavior 30 days after CCI. The anxiety-like behavior was associated with a significant loss of GABAergic interneurons and significant reductions in the frequency and amplitude of spontaneous and miniature GABA_A-receptor-mediated inhibitory postsynaptic currents (IPSCs) in the BLA. Significantly, subchronic treatment with alpha-linolenic acid (ALA) after CCI prevents the development of anxiety-like behavior, the loss of GABAergic interneurons, hyperexcitability in the BLA and reduces the impact injury. Taken together, administration of ALA after CCI is a potent therapy against the neuropathology and pathophysiological effects of mTBI in the BLA.     

The Tropical managed Forests Observatory: a research network addressing the future of tropical logged forests

While attention on logging in the tropics has been increasing, studies on the long-term effects of silviculture on forest dynamics and ecology remain scare and spatially limited. Indeed, most of our knowledge on tropical forests arises from studies carried out in undisturbed tropical forests. This bias is problematic given that logged and disturbed tropical forests are now covering a larger area than the so-called primary forests. A new network of permanent sample plots in logged forests, the Tropical managed Forests Observatory (TmFO), aims to fill this gap by providing unprecedented opportunities to examine long-term data on the resilience of logged tropical forests at regional and global scales. TmFO currently includes 24 experimental sites distributed across three tropical regions, with a total of 490 permanent plots and 921 ha of forest inventories.     

Solid-state synthesis of cyclo LD-diphenylalanine: A chiral phase built from achiral subunits

The solid-state structure of LL/DD or LD/DL diphenylalanine diluted in KBr pellets is studied by infrared (IR) absorption and vibrational circular dichroism (VCD) spectroscopy. The structure depends on the absolute configuration of the residues. The natural LL diphenylalanine exists as a mixture of neutral and zwitterionic structures, depending on the humidity of the sample, while mostly the zwitterion is observed for LD diphenylalanine whatever the experimental conditions. The system undergoes spontaneous cyclization upon heating at 125°C, resulting to the formation of a diketopiperazine (DKP) dipeptide as the only product. The reaction is faster for LD than for LL diphenylalanine. As expected, LL and DD diphenylalanine react to form the LL and DD enantiomers of cyclo diphenylalanine. Interestingly, the DKP dipeptides formed from the LD or DL diphenylalanine show unexpected optical activity, with opposite VCD spectra for the products formed from the LD and DL reagents. This is explained in terms of chirality synchronization between the monomers within the crystal, which retain the symmetry of the reagent, resulting to the formation of a new chiral phase made from transiently chiral molecules.