Estimating seed dispersal distance: A comparison of methods using animal movement and plant genetic data on two primate‐dispersed Neotropical plant species

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An Overview of the Biology of Reaction Wood Formation

Reaction wood possesses altered properties and performs the function of regulating a tree＇s form, but it is a serious defect in wood utility. Trees usually develop reaction wood in response to a gravistimulus. Reaction wood in gymnosperms is referred to as compression wood and develops on the lower side of leaning stems or branches. In arboreal, dicotyledonous angiosperms, however, it is called tension wood and is formed on the upper side of the leaning. Exploring the biology of reaction wood formation is of great value for the understanding of the wood differentiation mechanisms, cambial activity, gravitropism, and the systematics and evolution of plants. After giving an outline of the variety of wood and properties of reaction wood, this review lays emphasis on various stimuli for reaction wood induction and the extensive studies carried out so far on the roles of plant hormones in reaction wood formation. Inconsistent results have been reported for the effects of plant hormones. Both auxin and ethylene regulate the formation of compression wood in gymnosperms. However, the role of ethylene may be indirect as exogenous ethylene cannot induce compression wood formation. Tension wood formation is mainly regulated by auxin and gibberellin. Interactions among hormones and other substances may play important parts in the regulation of reaction wood formation.     

Genetic structure and domestication footprints of the tusk,coat color,and ear morphology in East Chinese pigs

The domestication and artificial selection of wild boars have led to dramatic morphological and behavioral changes, especially in East Chinese (ECN) pigs. Here, we provide insights into the population structure and current genetic diversity of representative ECN pig breeds. We identify a 500-kb region containing six tooth development-relevant genes with almost completely different haplotypes between ECN pigs and Chinese wild boars or European domestic pigs. Notably, the c.195A>G missense mutation in exon 2 of AMBN may cause alterations in its protein structure associated with tusk degradation in ECN pigs. In addition, ESR1 may play an important role in the reproductive performance of ECN pigs. A major haplotype of the large lop ear-related MSRB3 gene and eight alleles in the deafness-related GRM7 gene may affect ear morphology and hearing in ECN pigs. Interestingly, we find that the two-end black (TEB) coat color in Jinhua pigs is most likely caused by EDNRB with genetic mechanisms different from other Chinese TEB pigs. This study identifies key loci that may be artificially selected in Chinese native pigs related to the tusk, coat color, and ear morphology, thus providing new insights into the genetic mechanisms of domesticated pigs.     

Atomistic modelling of interface structure and deformation mechanisms in the Al/GaN multilayer under compression

The properties of ohmic contact and thermal boundary conductance between Al and GaN have been studied extensively, but the interface structures and deformation mechanisms in the Al/GaN multilayer can be rarely found in literatures. By molecular dynamics (MD) simulations, we systematically studied the interface structures and structural deformations in the Al/GaN multilayer. Two kinds of interface structures are identified according to the different terminal surfaces of GaN; glide-set terminal interface and shuffle-set terminal interface. Further analysis shows that interface has the maximum stress and misfit lines have the maximum stress values, which serve as the dislocation sources in the Al layer due to the larger stress in the interface. The mechanical responses of the Al/GaN multilayer exhibit a minor stage and some distinctive drops in the stress–strain curve. The first stage is associated with the dislocation nucleation from the interface. Upon further compression, more slip systems appear in the Al layer and dislocation nucleation in GaN could induce drops in curves. Meanwhile, the multiplications of dislocations cause strain hardening behaviours.     

Moderate activation of Wnt/β-catenin signaling promotes the survival of rat nucleus pulposus cells via regulating apoptosis,autophagy, and senescence

This study aimed to investigate the specific role of Wnt/β-catenin signaling in compression-induced apoptosis, autophagy, and senescence in rat nucleus pulposus (NP) cells. Initially, the cells underwent various periods of exposure to 1.0 MPa compression. Wnt/β-catenin signaling associated molecules were assessed in detail, and then 0, 24 and 48 hours exposure periods were selected. The cells were then divided into control, Wnt/β-catenin inhibitor (IWP-2), Wnt/β-catenin activator (LiCl), and β-catenin overexpression groups. After 0, 24, and 48 hours of compression, apoptosis, autophagy, and senescence were evaluated by Western blot analysis and real-time polymerase chain reaction and were visually observed by Hoechst33258, monodansylcadaverine, and SA-β-gal stainings, respectively. Additionally, the regulatory effect of Wnt/β-catenin signaling on cell morphology, viability, cell cycle, death ratio, and ultrastructure was detected to thoroughly evaluate the survival capacity of NP cells. The results established that compression elicited a time-dependent activation of Wnt/β-catenin signaling. The IWP-2 treatment decreased cell survival rate, which corresponded to downregulation of autophagy as well as increases in apoptosis and senescence. LiCl treatment enabled more efficient of cell survival accompanied by increased autophagy and downregulated apoptosis and senescence; however, in contrast to LiCl, overexpression of β-catenin aggravated compression-induced NP cells death. In conclusion, moderate activation of Wnt/β-catenin signaling enables more efficient of NP cells survival via downregulation of apoptosis, senescence, and upregulation of autophagy, and overactivation of Wnt/β-catenin signaling achieved the opposite effect. Treatment strategies that aim to regulate Wnt/β-catenin signaling might be a novel target for improving compression-induced NP cells death and potential treatment of intervertebral disc degeneration.     

Genetic heterogeneity at the bovine KIT gene in cattle breeds carrying different putative alleles at the spotting locus

According to classical genetic studies, piebaldism in cattle is largely influenced by the allelic series at the spotting locus (S), which includes the S^H (Hereford pattern), S⁺ (non‐spotted) and s (spotted) alleles. The S locus was mapped on bovine chromosome 6 in the region containing the KIT gene. We investigated the KIT gene, analysing its variability and haplotype distribution in cattle of three breeds (Angus, Hereford and Holstein) with different putative alleles (S⁺, S^H and s respectively) at the S locus. Resequencing of a whole of 0.485 Mb revealed 111 polymorphisms. The global nucleotide diversity was 0.087%. Tajima’s D‐values were negative for all breeds, indicating putative directional selection. Of the 28 inferred haplotypes, only five were observed in the Hereford breed, in which one was the most frequent. Coalescent simulation showed that it is highly unlikely (P < 10E‐6) to obtain this low number of haplotypes conditionally on the observed number of segregating SNPs. Therefore, the neutral model could be rejected for the Hereford breed, suggesting that a selection sweep occurred at the KIT locus. Twelve haplotypes were inferred in Holstein and Angus. For these two breeds, the neutral model could not be rejected. High heterogeneity of the KIT gene was confirmed from a phylogenetic analysis. Our results suggest a role of the KIT gene in determining the S^H allele(s) in the Hereford, but no evidence of selective sweep was obtained in Holstein, suggesting that complex mechanisms (or other genes) might be the cause of the spotted phenotype in this breed.     

Mammalian Retromer Is an Adaptable Scaffold for Cargo Sorting from Endosomes

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Appearance of “β-Like” Circular Dichroism Spectra on Protein Aggregation That Is not Accompanied by Transition to β-Structure

CD spectra in the 200 to 250 nm spectral region for small ordered aggregates (trimers-pentamers) of tobacco mosaic virus (TMV) coat protein (CP) and for long virus-like helical aggregates of TMV CP were compared. It was found that small (4S) TMV CP aggregates have a CD spectrum typical of a protein with high -helix content, which agrees well with results of X-ray diffraction studies. But in the long helical aggregates (and in the TMV virions) TMV CP gives -like CD spectra similar to those of many other aggregated proteins. From X-ray diffraction data, it is well known that TMV CP subunits do not change their secondary or tertiary structure on assembly into virions or the helical repolymerized protein. Thus, the change in the shape of 200 to 250 nm CD spectra cannot be employed as the sole criterion of the conversion of a protein to -structure in the course of aggregation.     

Evolution of egg target size: an analysis of selection on correlated characters

In broadcast-spawning marine organisms, chronic sperm limitation should select for traits that improve chances of sperm-egg contact. One mechanism may involve increasing the size of the physical or chemical target for sperm. However, models of fertilization kinetics predict that increasing egg size can reduce net zygote production due to an associated decline in fecundity. An alternate method for increasing physical target size is through addition of energetically inexpensive external structures, such as the jelly coats typical of eggs in species from several phyla. In selection experiments on eggs of the echinoid Dendraster excentricus, in which sperm was used as the agent of selection, eggs with larger overall targets were favored in fertilization. Actual shifts in target size following selection matched quantitative predictions of a model that assumed fertilization was proportional to target size. Jelly volume and ovum volume, two characters that contribute to target size, were correlated both within and among females. A cross-sectional analysis of selection partitioned the independent effects of these characters on fertilization success and showed that they experience similar direct selection pressures. Coupled with data on relative organic costs of the two materials, these results suggest that, under conditions where fertilization is limited by egg target size, selection should favor investment in low-cost accessory structures and may have a relatively weak effect on the evolution of ovum size.     

Biophysical characterization of a designed TMV coat protein mutant, R46G, that elicits a moderate hypersensitivity response in Nicotiana sylvestris

The hypersensitivity resistance response directed by the N' gene in Nicotiana sylvestris is elicited by the tobacco mosaic virus (TMV) coat protein R46G, but not by the U1 wild-type TMV coat protein. In this study, the structural and hydrodynamic properties of R46G and wild-type coat proteins were compared for variations that may explain N' gene elicitation. Circular dichroism spectroscopy reveals no significant secondary or tertiary structural differences between the elicitor and nonelicitor coat proteins. Analytical ultracentrifugation studies, however, do show different concentration dependencies of the weight average sedimentation coefficients at 4 degrees C. Viral reconstitution kinetics at 20 degrees C were used to determine viral assembly rates and as an initial assay of the rate of 20S formation, the obligate species for viral reconstitution. These kinetic results reveal a decreased lag time for reconstitution performed with R46G that initially lack the 20S aggregate. However, experiments performed with 20S initially present reveal no detectable differences indicating that the mechanism of viral assembly is similar for the two coat protein species. Therefore, an increased rate of 20S formation from R46G subunits may explain the differences in the viral reconstitution lag times. The inferred increase in the rate of 20S formation is verified by direct measurement of the 20S boundary as a function of time at 20 degrees C using velocity sedimentation analysis. These results are consistent with the interpretation that there may be an altered size distribution and/or lifetime of the small coat protein aggregates in elicitors that allows N. sylvestris to recognize the invading virus.