Morphological and Ultrastructural Features of Formation of the Skin of Wheat (Triticum aestivum L.) Kernel

The integumentary tissues of plant seeds protect the embryo (new sporophyte) forming in them from unfavorable external conditions; therefore, comprehensive knowledge about the structural and functional specificity of seed covers in various plants may be of both theoretical and practical interest. As a result of our study, additional data were obtained on the morphological and ultrastructural features of the formation of a multilayer skin of wheat (Triticum aestivum L.) kernel (caryopsis). The ultrastructure research analysis showed that differentiation of the pericarp and inner integument of the ovule leads to the formation of functionally different layers of the skin of mature wheat grain. Thus, the differentiation of exocarp and endocarp cells is accompanied by a significant thickening of the cell walls, which reliably protect the ovule from adverse external conditions. The cells of the two-layer inner integument of the ovule differentiate into cuticular and phenolic layers, which are critical for protecting daughter tissues from various pathogens. The epidermis of the nucellus turns into a layer of mucilage, which apparently helps to maintain the water balance of the seed. Morphological and ultrastructural data showed that the formation of the kernel's skin occurs in coordination with the development of the embryo and endosperm up to the full maturity of the kernel. This is evidenced by the structure of the cytoplasm and nucleus, characteristic of metabolically active protoplasts of cells, which is observed in most integumentary layers at the late stages of maturation. This activity can also be confirmed by a significant increase in the thickness of the cell walls in the cells of two layers of the exocarp and in cross cells in comparison with the earlier stages. Based on these results, we came to the conclusion that the cells of a majority in the covering tissues of the wheat kernel during its ontogenesis are transformed into specialized layers of the skin by terminal differentiation.

Rice caryopsis development I: Dynamic changes in different cell layers

Rice caryopsis as one of the most important food sources for humans has a complex structure that is composed of maternal tissues including the pericarp and testa and filial tissues including the endosperm and embryo. Although rice caryopsis studies have been conducted previously, a systematic characterization throughout the entire developmental process is still lacking. In this study, detailed morphological examinations of caryopses were made during the entire 30-day developmental process. We observed some rapid changes in cell differentiation events and cataloged how cellular degeneration processes occurred in maternal tissues. The differentiations of tube cells and cross cells were achieved by 9 days after pollination (DAP). In the testa, the outer integument was degenerated by 3 DAP, while the outer layer of the inner integument degenerated by 7 DAP. In the nucellus, all tissues with the exception of the nucellar projection and the nucellar epidermis degenerated in the first 5 DAP. By 21 DAP, all maternal tissues, including vascular bundles, the nucellar projection and the nucellar epidermal cells were degenerated. In summary, this study provides a complete atlas of the dynamic changes in cell differentiation and degeneration for individual maternal cell layers of rice caryopsis.

Cell layer-electrospun mesh composites for coronary artery bypass grafts

This work investigates the potential of cell layer-electrospun mesh constructs as coronary artery bypass grafts. These cell-mesh constructs were generated by first culturing a confluent layer of 10T½ smooth muscle progenitor cells on a high strength electrospun mesh with uniaxially aligned fibers. Cell-laden mesh sheets were then wrapped around a cylindrical mandrel such that the mesh fibers were aligned circumferentially. The resulting multi-layered constructs were then cultured for 4 wks in media supplemented with TGF-β1 and ascorbic acid to support 10T½ differentiation toward a smooth muscle cell-like fate as well as to support elastin and collagen production. The underlying hypothesis of this work was that extracellular matrix (ECM) deposited by the cell layers would act as an adhesive agent between the individual mesh layers, providing strength to the construct as well as a source for structural elasticity at low strains. In addition, the structural anisotropy of the mesh would inherently guide desired circumferential cell and ECM alignment. Results demonstrate that the cell-mesh constructs exhibited a J-shaped circumferential stress-strain response similar to that of native coronary artery, while also displaying acceptable tensile strength. Furthermore, associated 10T½ cells and deposited collagen fibers showed a high degree of circumferential alignment. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2200-2209, 2016.