Distinct Differentiation Characteristics of Endothelium Determine Its Ability to Form Pseudo-Embryos in Tomato Ovules

Abstract

The endothelium is an additional cell layer, differentiating from the inner epidermis of the ovule integument. In tomato (Solanum lycopersicum L.), after fertilization, the endothelium separates from integument and becomes an independent tissue developing next to the growing embryo sac. In the absence of fertilization, the endothelium may proliferate and form pseudo-embryo. However, the course of the reorganization of endothelium into pseudo-embryo in tomato ovules is poorly understood. We aimed to investigate specific features of endothelium differentiation and the role of the endothelium in the development of fertilized and unfertilized tomato ovules. The ovules of tomato plants (“YaLF” line), produced by vegetative growth plants of transgenic tomato line expressing the ac gene, encoding chitin-binding protein from Amaranthus caudatus L., were investigated using light and transmission electron microscopy. We showed that in the fertilized ovule of normally developing fruit and in the unfertilized ovule of parthenocarpic fruit, separation of the endothelium from integument occurs via programmed death of cells of the integumental parenchyma, adjacent to the endothelium. Endothelial cells in normally developing ovules change their structural and functional specialization from meristematic to secretory and back to meristematic, and proliferate until seeds fully mature. The secretory activity of the endothelium is necessary for the lysis of dying cells of the integument and provides the space for the growth of the new sporophyte. However, in ovules of parthenocarpic fruits, pseudo-embryo cells do not change their structural and functional organization and remain meristematic, no zone of lysis is formed, and pseudo-embryo cells undergo programmed cell death. Our data shows the key role of the endothelium as a protective and secretory tissue, needed for the normal development of ovules.

Corneal Endothelial Characteristics in Normal Chinese Han Children and Youngsters: A Study from the Specular Microscopy Descriptions

“…Those data affirm that the different endothelial qualifications such as ECD and hexagonality reach the evaluation dimensions consistency which coincide with Joo et al's publications [23]. The size and hexagon of endothelial cell area can be the unique property for the human develop-ment [24]. Meanwhile, Radman et al's literatures have reported that the sharp of the human endothelial be associated with the age growth stage, even that so-called childhood obesity criterion can be realized fiercely different with adolescence and earlier adulthood [25].…”

Morphological Features of the Anther Development in Tomato Plants with Non-Specific Male Sterility

“…The endothelium in the tomato ovule is the internal epidermis of integument, transformed into an independent tissue. In the early stages of embryo development, the endothelium separates and protects the developing endosperm from dying integumental parenchyma cells due to PCD [18]. Tapetal cells in anthers during pollen formation completely degenerates, while the endothelium in tomato ovules remains practically until the seed fully matures.…”

“…Nevertheless, apparently, due to the hormonal deviations in cells around the embryo sac, so-called pseudo-embryonic tissue is formed in the unfertilized ovules from the inner epidermis of the integument. In turn, it stimulates the ovary to develop and form parthenocarpic fruits [18].The aim of this work was to identify the cytoembryological features of anthers and pollen development to establish morphological factors for pollen sterility at key stages of the androecium and gynoecium development in transgenic tomato plants with anomalies of generative organs, as well as in transgenic tomatoes without visible phenotypic anomalies, but with partially sterile pollen. These model tomato plants were previously used to study pseudo-embryo formation in the ovules of parthenocarpic fruits [18].…”

“…Nevertheless, apparently, due to the hormonal deviations in cells around the embryo sac, so-called pseudo-embryonic tissue is formed in the unfertilized ovules from the inner epidermis of the integument. In turn, it stimulates the ovary to develop and form parthenocarpic fruits [18].…”

Morphological and Structural Details of Tomato Seed Coat Formation: A Different Functional Role of the Inner and Outer Epidermises in Unitegmic Ovule

“…In our previous research, a detailed electron microscopic study of the ovule histogenesis in normal and genetically transformed tomatoes was carried out to reveal the cytoembryological causes of the endothelium growth and its transformation into pseudo-embryonic tissue in the ovules of transgenic tomatoes [11]. It was revealed that the mechanism of the detachment process of the inner epidermis from integument is the programmed death of adjacent parenchyma cells of the integument itself [11]. Ricinosomes, which are the markers of PCD, were found in these cells [12].…”