Hybrid Decay: A Transgenerational Epigenetic Decline in Vigor and Viability Triggered in Backcross Populations of Teosinte with Maize.

In the course of generating populations of maize with teosinte chromosomal introgressions, an unusual sickly plant phenotype was noted in individuals from crosses with two teosinte accessions collected near Valle de Bravo, Mexico. The plants of these Bravo teosinte accessions appear phenotypically normal themselves and the F1 plants appear similar to typical maize × teosinte F1s. However, upon backcrossing to maize, the BC1 and subsequent generations display a number of detrimental characteristics including shorter stature, reduced seed set, and abnormal floral structures. This phenomenon is observed in all BC individuals and there is no chromosomal segment linked to the sickly plant phenotype in advanced backcross generations. Once the sickly phenotype appears in a lineage, normal plants are never again recovered by continued backcrossing to the normal maize parent. Whole-genome shotgun sequencing reveals a small number of genomic sequences, some with homology to transposable elements, that have increased in copy number in the backcross populations. Transcriptome analysis of seedlings, which do not have striking phenotypic abnormalities, identified segments of 18 maize genes that exhibit increased expression in sickly plants. A de novo assembly of transcripts present in plants exhibiting the sickly phenotype identified a set of 59 upregulated novel transcripts. These transcripts include some examples with sequence similarity to transposable elements and other sequences present in the recurrent maize parent (W22) genome as well as novel sequences not present in the W22 genome. Genome-wide profiles of gene expression, DNA methylation, and small RNAs are similar between sickly plants and normal controls, although a few upregulated transcripts and transposable elements are associated with altered small RNA or methylation profiles. This study documents hybrid incompatibility and genome instability triggered by the backcrossing of Bravo teosinte with maize. We name this phenomenon "hybrid decay" and present ideas on the mechanism that may underlie it

Templateâ Directed Solidification of Eutectic Optical Materials

Mesostructured materials can exhibit enhanced lightâ matter interactions, which can become particularly strong when the characteristic dimensions of the structure are similar to or smaller than the wavelength of light. For controlling visible to nearâ infrared wavelengths, the small characteristic dimensions of the required structures usually demand fabrication by sophisticated lithographic techniques. However, these fabrication methods are restricted to producing 2D and a limited range of 3D structures. When a large volume of structured material is required, the primary approach is to use selfâ assembly, and the literature includes many examples of mesostructured optical materials formed via selfâ assembly. However, selfâ organized materials almost always contain structural imperfections which limit their performance. Emerging work, however, is showing that by performing selfâ assembly within a guiding template, the defect density in selfâ assembled structures can be reduced. Particularly interesting is the possibility that utilizing a template can result in the formation of mesostructures not present in either the template or the native selfâ organizing material. In this review, particular emphasis is placed on emerging results showing the effect of mesoscale templates on the microstructure of solidifying eutectic materials, with a specific focus on how templateâ directed solidification may be a powerful approach for fabricating optically active structures, including optical metamaterials.Templateâ directed assembly gives access to structures that are not present in either the template or the native selfâ organizing material. Proofâ ofâ concept works on templateâ directed selfâ organization of solidifying eutectic materials have exhibited intriguing results for photonics and optical metamaterials. This article provides a review of the challenges and opportunities of this technique for forming optically powerful structures.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/144275/1/adom201800071_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/144275/2/adom201800071.pd

Synthesis and characterization of poly(vinyl chloride-g-epsilon-caprolactone) brush type graft copolymers by ring-opening polymerization and "click" chemistry

WOS: 000491969100001Synthesis of poly(vinyl chloride-g-epsilon-caprolactone) [poly(VC-g-CL)] brush type graft copolymers were archived by "click" chemistry of polyvinyl chloride propargyl (PVC-propargyl) and terminally azido poly(epsilon-caprolactone) ester (PCL-N-3). For this purpose, 2-(2-azidoethoxy)ethan-1-ol (N-3-ol) was obtained by reaction of 2-(2-chloroethoxy)ethan-1-ol and sodium azide. Synthesis of PCL-N-3 was carried out by means of ring-opening polymerization (ROP) of epsilon-caprolactone and N-3-ol. Furthermore, PCL-N-3 was synthesized by using polycaprolactone and N-3-ol. PVC-propargyl was obtained by the reaction of purified polyvinyl chloride with propargyl alcohol. By using PCL-N-3 and PVC-propargyl, poly(VC-g-CL) brush type graft copolymers were obtained via "click" chemistry. The products were characterized by H-1-nuclear magnetic resonance spectroscopy (H-1-NMR), Fourier-transform infrared spectroscopy (FT-IR), gel permeation chromatography (GPC), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The multi instruments studies of the brush type graft copolymers show that the graft copolymers easily built as a result of combination of "click" chemistry and ROP. This work is an example of a type of combination reaction, from ROP to "click" chemistry. The synthesis pathways of this study can pioneer to newer and well-designed materials for wide range applications. This method for synthesis of graft copolymer is simple and efficient