Temporal Markers in Plant Morphogenesis

In plants as well as in animals, time may be registered in permanent structures at all organization levels. In this brief review, some examples of spatial rhythmic patterns related to plant morphogenesis and as far as possible the underlying mechanisms will be described. In conclusion, the practical interest of these structures will be emphazised.     

Polyamines and Plant Morphogenesis

Alterations in free and conjugated polyamines (PAs) and the enzymes involved in their biosynthesis, namely arginine decarboxylase, ornithine decarboxylase and S-adenosyl methionine decarboxylase have been reported to occur during cell division, growth, embryogenesis and rhizogenesis in an array of plant materials. However, the relationship, if any, between them and all these processes has not yet been established. It seems that specific PAs at specific concentration ranges are required during critical stages of growth and morphogenetic events. Furthermore, the effects of PA biosynthesis inhibitors vary considerably at different developmental stages of the same tissue. The present review deals with the available information about the possible role of PAs in aforesaid physiological processes.     

Circamensal Rhythms in Physical Performance

The eumenorrheic menstrual cycle represents a clear inherent biological rhythm that might interact with both physical performance, and/or the physiological response to performance. The predominant hormonal fluctuations throughout the cycle are in the ovarian steroids oestrogen and progesterone. Progesterone has both a thermogenic and ventilatory effect leading to a potential increase in minute ventilation and body temperature during exercise. Oestrogen has been linked to fluctuations in blood flow and heart rate via a vasodilatory mechanism, plus potential variation in muscle strength. If these hormones do indeed influence physical performance, or the physiological response to performance, female athletes might choose to manipulate the cycle through an endogenous hormonal mechanism. Furthermore, researchers utilizing a female population must control for these fluctuations in their research design.     

Arabinogalactan Proteins: Involvement in Plant Growth and Morphogenesis

Arabinogalactan proteins (AGPs) are highly glycosylated hydroxyproline-containing variously located proteoglycans dynamically regulated in the course of plant ontogenesis. Special functions of AGPs are still unclear, but their involvement in vegetative growth and reproduction of plants is well established. This review considers data on the structure, biosynthesis, and metabolism of AGPs. Special attention is given to involvement of AGPs in growth and morphogenesis, and possible mechanisms of their regulatory action are considered. AGPs are also compared with animal proteoglycans.     

Tomato Spotted Wilt Virus Particle Morphogenesis in Plant Cells

A model for the maturation of tomato spotted wilt virus (TSWV) particles is proposed, mainly based on results with a protoplast infection system, in which the chronology of different maturation events could be determined. By using specific monoclonal and polyclonal antisera in immunofluorescence and electron microscopy, the site of TSWV particle morphogenesis was determined to be the Golgi system. The viral glycoproteins G1 and G2 accumulate in the Golgi prior to a process of wrapping, by which the viral nucleocapsids obtain a double membrane. In a later stage of the maturation, these doubly enveloped particles fuse to each other and to the endoplasmic reticulum to form singly enveloped particles clustered in membranes. Similarities and differences between the maturation of animal-infecting (bunya)viruses and plant-infecting tospoviruses are discussed.     

Temporal organization in a morphogenetic field

We have investigated the possibility of self-sustained oscillations of chemical concentrations during morphogenetic processes. In particular, we have shown that, in the case of the Gierer-Meinhardt model, self-sustained oscillations are possible when an order parameter, connected with the decay constants of morphogenes, crosses a critical value. The analytical results are in agreement with the numerical results of Gierer and Meinhardt.     

Studies of Temporal and Spatial Peculiarities of Somitogenesis in Fish Embryos

New data were obtained corroborating that somitogenesis is a rhythmic process, in which the time of somite formation is strictly constant. This constant ( _s ) can be considered as a natural unit of developmental biological clock characterizing rhythmic processes. The constant _s can be determined with an exceptional accuracy that has no analogs among the known biological processes. This fact alone suggests that the accuracy of developmental clock is very high. In addition to the constancy of _s , all forming somites have equal linear size along the notochord axis. In the process with strictly constant temporal and spatial factors, time plays the leading role in triggering the formation of new somite. This became clear in studies of twin embryos. Both embryos had the same number of somites but they were shorter than in the normal embryos. Also, we measured the length of head and both segmented and unsegmented caudal parts of the trunk. Combined with the published data on somitogenesis, our results suggest that the previously proposed scheme for the role of developmental clock in embryogenesis predicts: (1) a possible loss of some embryonic stages without serious consequences for subsequent development and (2) periodic switching on/off any embryonic processes (at the molecular, cellular, or supercellular level) with intervals multiple to _s .     

植物反转录转座子及其分子标记

反转录转座子(retrotransposon)是真核生物中一类可移动因子,可分为m反转录转座子和非LTR反转录转座子。反转录转座子以高拷贝在植物界广泛分布,可以通过纵向和横向分别在世代之间和不同种之间进行传递,同一家族的反转录转座子具有高度的异质性．在一些生物的和非生物的逆境条件下,反转录转座子的转录可以被激活。由于反转录转座子的特点,使其作为一种分子标记得以应用。SSAP、IRAP、REMAP和RBIP等分子标记相继发展起来,在基因作图、生物遗传多样性与系统进化、品种鉴定等方面具有广泛的应用前景。     

基于逆转座子的植物分子标记技术及其应用

逆转座子特异的结构和功能使其作为一种有效的遗传工具应用于许多方面。本文就植物逆座子的组成、类别、以及其作为分子标记体系应用在遗传多样性、种系发生和基因作图等的新进展作一综述。     

Morphogenesis in Relation to Chromosomal Constitution in Long-term Plant Tissue Cultures

A number of strains of callus tissues derived from 1-mm root tips of the garden pea, Pisum sativum L., cultivated on a complex medium containing yeast extract and 2, 4-D for eight years, were tested periodically for their capacity to initiate roots. Chromosomal cytological analyses accompanied each test. It was found that during the prolonged period of subculture there was a progressive loss of organ-forming Capacity in all tissue strains. At the outset all callus tissues could be stimulated to form normal diploid roots. After several years of continuous subculture, some callus tissues formed normal tetraploid roots. Still later, these callus tissues lost completely the capacity to initiate roots. This loss was paralleled by increasing abnormalities in the chromosomal constitution, including higher chromosome numbers and greater frequency of aneuploidy. Early in subculture normal diploid and tetraploid divisions were present in the callus tissues. Later, higher polyploids at 8n and 16n were more frequent, as well as aneuploids around these numbers. Some tissue strains after prolonged cultivation showed a wide range of chromosome numbers at the higher ploidy levels but completely lacked diploid divisions. It is suggested that the loss in organ-forming capacity is correlated with the increase in abnormality of chromosomal constitution. Differentiation of certain characteristic cell types was unaffected by these changes.     

Relationship between immunoglobulin levels and extremes of solar activity

The possible relationship between epidemics and extremes of solar activity has been discussed previously. The purpose of the present study was to verify whether differences in the levels of immunoglobulins (IgA, IgG, IgM) could be noted at the highest (July 1989) and lowest (September 1986) points of the last (21st) and present (22nd) 11-year solar cycle. The work was divided into a 1-month study (covering the month of minimal or maximal solar activity), a 3-month study (1 month before and after the month of minimal or maximal solar activity) and a 5-month study (2 months before and after the month of minimal or maximal solar activity). A trend of a drop-off for all three immunoglobulins was seen on the far side of the maximal point of the solar cycle. Statistical significance was achieved in the 5-month study for IgM (P=0.04), and a strong trend was shown for IgG (P=0.07). Differences between the sexes were also noted.     

Plant Growth and Morphogenesis in vitroIs Promoted by Associative Methylotrophic Bacteria

The effects of aerobic methylotrophic bacteria Methylovorus mayson growth and morphogenesis were studied in in vitropropagated tobacco, potato, and flax. Colonization of plant explants with the methylo-trophic bacteria led to the stable association of bacteria and plants and enhanced the growth and the capacity of the latter for regeneration and root formation. When colonized by the methylotrophic bacteria, the rootless transgenic tobacco plants carrying the agrobacterial cytokinin gene iptrestored their ability to form roots. These data indicate the possibility to employ methylotrophic bacteria as a tool in experimental biology and plant biotechnology.     

Reaction-Diffusion Patterns in Plant Tip Morphogenesis: Bifurcations on Spherical Caps

We study a chemical reaction-diffusion model (the Brusselator) for pattern formation on developing plant tips. A family of spherical cap domains is used to represent tip flattening during development. Applied to conifer embryos, we model the chemical prepatterning underlying cotyledon (“seed leaf”) formation, and demonstrate the dependence of patterns on tip flatness, radius, and precursor concentrations. Parameters for the Brusselator in spherical cap domains can be chosen to give supercritical pitchfork bifurcations of patterned solutions of the nonlinear reaction-diffusion system that correspond to the cotyledon patterns that appear on the flattening tips of conifer embryos.     

分子标记技术及其在植物遗传育种中的应用

本对遗传标记技术的发展历程作了简要的回顾。概述了目前常用的RFLP和RAPD等分子标记技术的基本原理和特点,及其在构建分子遗传图谱、品种间遗传关系分析、进行基因定位和测定遗传距离等遗传育种中的应用。     

海参生物活性研究进展

海参是重要的海洋食物和药物资源,含有多种生物活性成分,如多糖、皂苷、多肽及蛋白质和脂类等其他活性成分,具有增强免疫力、抗凝血、镇痛、抗肿瘤、抗真菌、抗病毒、抗衰老和抗疲劳等生理功能.本文简要介绍了我国海参资源的分布情况,综述了国内外对海参生物活性物质组成及其药理作用研究的新进展.旨在为科学工作者对海参展开细胞和分子水平上的研究、寻找新型的海洋高效药物和功能性食品的开发提供参考,同时为我国丰富的海参资源的开发利用提供新思路.     

The Effects of Varying Chromosome Arm Dosage on Maize Plant Morphogenesis

Maize is an especially well-suited species for studying the effects of aneuploidy on plant development. We used B-A translocations and testers that were crossed seven times into inbred W22 to generate a dosage series for 14 chromosome arms. This is the first report of dosage effects on maize morphogenesis using inbred B-A stocks and inbred tester stocks. We compared plants containing one dose or three doses of each of the 14 chromosome arms with plants containing two doses for seven measured traits. These were leaf width, leaf length, plant height, ear height, internode length, ear node circumference, and tassel branch number. We observed the typical maize aneuploid syndrome wherein one dose was more widespread and more severe in its effects than three doses. All but two of the one-dose effects were negative, and all of the three-dose effects were negative. The occurrence of positive responses by hyperploid plants in our earlier B-A-A study and the absence of any positive responses among the hyperploids reported for the 14 simple B-A translocations tested for dosage effects in the present study and previously may reflect gene dosage interaction between the two chromosome arm segments present in the B-A-A translocations. The overall congruence of our results with those of previous studies suggests that the traits measured are quantitative traits controlled by multiple genes whose activities provide a balanced regulation that transcends individual inbred lines or diverse genetic backgrounds and that such genes may be especially abundant in chromosome arm 1L.