Biomechanical analysis of the Rolled (RLD) leaf phenotype of maize

The pleiotropic effects of the Rld1-O/+ mutation of Zea mays (Poaceae) on leaf phenotype include a suppression of normal transverse unrolling, a reversed top/bottom epidermal polarity, and an apparently straighter longitudinal shape. According to engineering shell theory, there might be mechanical coupling between transverse and longitudinal habit, i.e., the leaf rolling itself might produce the longitudinal straightening. We tested this possibility with quantitative curvature measurements and mechanical uncoupling experiments. The contributions of elastic bending under self weight, mechanical coupling, and rest state of leaf parts to the longitudinal and transverse habit were assessed in Rld1-O/+ mutants and a population of sibling +/+ segregants. Elastic bending and curvature coupling are shown to be relatively unimportant. The Rld1-O/+ mutation is shown to alter not only the unrolling process, but also the developmental longitudinal curving in the growing leaf, leading to a straighter midrib and a rolled lamina. The Rld1-O/+ mutant is thus a suitable model to study the relation between tissue polarity and differential curvature development in the maize leaf. Since on the abaxial side of the leaf, more abundant sclerenchyma is found in +/+ than in Rld1-O/+, a gradient in sclerification may contribute to the development of midrib curvature.     

Development of the pollen grain and tapetum of wheat (Triticum aestivum) in untreated plants and plants treated with chemical hybridizing agent RH0007

Summary A study of pollen development in wheat was made using transmission electron microscopy (TEM). Microspores contain undifferentiated plastids and mitochondria that are dividing. Vacuolation occurs, probably due to the coalescence of small vacuoles budded off the endoplasmic reticulum (ER). As the pollen grain is formed and matures, the ER becomes distended with deposits of granular storage material. Mitochondria proliferate and become filled with cristae. Similarly, plastids divide and accumulate starch. The exine wall is deposited at a rapid rate throughout development, and the precursors appear to be synthesized in the tapetum. Tapetal cells become binucleate during the meiosis stage, and Ubisch bodies form on the plasma membrane surface that faces the locule. Tapetal plastids become surrounded by an electron-translucent halo. Rough ER is associated with the halo around the plastids and with the plasma membrane. We hypothesize that the sporopollenin precursors for both the Ubisch bodies and exine pollen wall are synthesized in the tapetal plastids and are transported to the tapetal cell surface via the ER. The microspore plastids appear to be involved in activities other than precursor synthesis: plastid proliferation in young microspores, and starch synthesis later in development. Plants treated with the chemical hybridizing agent RH0007 show a pattern of development similar to that shown by untreated control plants through the meiosis stage. In the young microspore stage the exine wall is deposited irregularly and is thinner than that of control plants. In many cases the microspores are seen to have wavy contours. With the onset of vacuolation, microspores become plasmolyzed and abort. The tapetal cells in RH0007-treated locules divide normally through the meiosis stage. Less sporopollenin is deposited in the Ubisch bodies, and the pattern is less regular than that of the control. In many cases, the tapetal cells expand into the locule. At the base of one of the locules treated with a dosage of RH0007 that causes 95% male sterility, several microspores survived and developed into pollen grains that were sterile. The conditions at the base of the locule may have reduced the osmotic stress on the microspores, allowing them to survive. Preliminary work showed that the extractable quantity of carotenoids in RHOOO7-treated anthers was slightly greater than in controls. We concluded that RH0007 appears to interfere with the polymerization of carotenoid precursors into the exine wall and Ubisch bodies, rather than interfering with the synthesis of the precursors.     

Localisation of acidic and basic fibroblast growth factors during mouse palate development and their effects on mouse palate mesenchyme cells in vitro

Summary The distribution of acidic and basic fibroblast growth factors (aFGF, bFGF) was mapped during mouse embryonic palate development. Generally, they localised most intensely in the basement membrane and epithelia rather than the mesenchyme. Localisation was predominantly restricted to the palatal nasal, and medial edge epithelia. Staining was particularly intense in the medial edge epithelia at the time of mid-line epithelial seam formation. Intense staining persisted in the epithelia of the degenerating seam and later in the oral and nasal epithelial triangles. Mouse embryonic palate mesenchyme (MEPM) cells cultured in vitro on a variety of substrata (on plastic, on the surface of a collagen gel and within a collagen gel) responded to treatment with aFGF or bFGF. These responses were modulated by the culture substratum. The FGFs stimulated MEPM cell proliferation on plastic and on collagen, but inhibited cell growth in collagen. The FGFs had little effect on protein production when cells were cultured on plastic, but caused a large reduction in on-collagen and incollagen cultures. This reduction was greater in collagenous than non-collagenous proteins. Generally, treatment with FGFs stimulated the production of glycosaminoglycans (GAGs), particularly hyaluronan (HA) and dermatan sulphate (DS). In addition, the size class of HA was shifted to a higher molecular weight form. These data indicate that aFGF and bFGF may play a role in modulating mesenchymal cell matrix biosynthesis, so facilitating palatal epithelial seam degeneration. Correspondence to: M.W.J. Ferguson     

Centrosome linker protein C‐Nap1 maintains stem cells in mouse testes

The centrosome linker component C‐Nap1 (encoded by CEP250) anchors filaments to centrioles that provide centrosome cohesion by connecting the two centrosomes of an interphase cell into a single microtubule organizing unit. The role of the centrosome linker during development of an animal remains enigmatic. Here, we show that male CEP250 ^−/− mice are sterile because sperm production is abolished. Premature centrosome separation means that germ stem cells in CEP250 ^−/− mice fail to establish an E‐cadherin polarity mark and are unable to maintain the older mother centrosome on the basal site of the seminiferous tubules. This failure prompts premature stem cell differentiation in expense of germ stem cell expansion. The concomitant induction of apoptosis triggers the complete depletion of germ stem cells and consequently infertility. Our study reveals a role for centrosome cohesion in asymmetric cell division, stem cell maintenance, and fertility.     

温度对圆尾肖蛸个体发育和繁殖力的影响

圆尾肖蛸(Tetragnotha vermiformis)在我国广泛分布于棉田、稻田、森林、果园。该蜘蛛具有捕食多种农作物害虫的能力,在湖堤、河岸、沟边更是蚊虫的有效天敌。本文仅就圆尾肖蛸的历期和繁殖力与温度的关系方面的试验结果进行了整理,并力图建立相应的数学模型,旨在为保护和利用工作提供科学依据。     

WNT5A signaling affects pituitary gland shape

Wnt signaling is important in organogenesis, and aberrant signaling in mature cells is associated with tumorigenesis. Several members of the Wnt family of signaling molecules are expressed in the developing pituitary gland. Wnt5a is expressed in the neuroectoderm that induces pituitary gland development and has been proposed to influence pituitary cell specification. We discovered that mice deficient in Wnt5a display abnormal morphology in the dorsal part of the developing pituitary. The expression of downstream effectors of the canonical Wnt pathway is not altered, and expression of genes in other signaling pathways such as Shh, Fgf8, Fgf10 and Fgfr2b is intact. Prop1 and Hesx1 are also important for normal shape of the pituitary primordium, but their expression is unaltered in the Wnt5a mutants. Specification of the hormone-producing cell types of the mature anterior pituitary gland occurs appropriately. This study suggests that the primary role of Wnt5a in the developing pituitary gland is in establishment of the shape of the gland.     

Characterization of zebrafish mutants with defects in bone calcification during development

Using the fluorescent dyes calcein and alcian blue, we stained the F3 generation of chemically (ENU) mutagenized zebrafish embryos and larvae, and screened for mutants with defects in bone development. We identified a mutant line, bone calcification slow (bcs), which showed delayed axial vertebra calcification during development. Before 4–5 days post-fertilization (dpf), the bcs embryos did not display obvious abnormalities in bone development (i.e., normal number, size and shape of cartilage and vertebrae). At 5–6 dpf, when vertebrae calcification starts, bcs embryos began to show defects. At 7 dpf, for example, in most of the bcs embryos examined, calcein staining revealed no signals of vertebrae mineralization, whereas during the same developmental stages, 2–14 mineralized vertebrae were observed in wild-type animals. Decreases in the number of calcified vertebrae were also observed in bcs mutants when examined at 9 and 11 dpf, respectively. Interestingly, by 13 dpf the defects in bcs mutants were no longer evident. There were no significant differences in the number of calcified vertebrae between wild-type and mutant animals. We examined the expression of bone development marker genes (e.g., Sox9b, Bmp2b, and Cyp26b1, which play important roles in bone formation and calcification). In mutant fish, we observed slight increases in Sox9b expression, no alterations in Bmp2b expression, but significant increases in Cyp26b1 expression. Together, the data suggest that bcs delays axial skeletal calcification, but does not affect bone formation and maturation.     

Oocyte Mitochondria: Strategies to Improve Embrbryogenesis

Abstract  Mitochondria play a central role to provide ATP for fertilization and preimplantation embryo development in the ooplasm. The mitochondrial dysfunction of oocyte has been proposed as one of the causes of high levels of developmental retardation and arrest that occur in preimplantation embryos generated using Assisted Reproductive Technology. Cytoplasmic transfer (CT) from a donor to a recipient oocyte has been applied to infertility due to dysfunctional ooplasm, with resulting pregnancies and births. However, neither the efficacy nor safety of this procedure has been appropriately investigated. In order to improve embryogenesis, we observed the mitochondrial distribution in ooplasma under the several conditions using mitochondrial GFP-transgenic mice (mtGFP-tg mice) in which the mitochondria are visualized by GFP. In this report, we will present our research about the mitochondrial distribution in ooplasm during early embryogenesis and the fate of injected donor mitochondria after CT using mtGFP-tg mice. The mitochondria in ooplasm from the germinal vesicle stage to the morula stage were accumulated in the perinuclear region. The mitochondria of the mtGFP-tg mouse oocyte transferred into the wild type mouse embryo could be observed until the blastocysts stage, suggesting that the mtGFP-tg mice oocyte is very useful for visual observation of the mitochondrial distribution in the oocyte, and that the aberrant early developmental competences due to the oocyte mitochondrial dysfunction may be overcome by transferring the "normal" mitochondria.